<?PHP // $Id$

/// FUNCTIONS FOR DATABASE HANDLING  ////////////////////////////////

function execute_sql($command, $feedback=true) {
/// Completely general function - it just runs some SQL and reports success.

    global $db;
    
    $result = $db->Execute("$command");

    if ($result) {
        if ($feedback) {
            echo "<P><FONT COLOR=green><B>".get_string("success")."</B></FONT></P>";
        }
        return true;
    } else {
        if ($feedback) {
            echo "<P><FONT COLOR=red><B>".get_string("error")."</B></FONT></P>";
        }
        return false;
    }
}

function modify_database($sqlfile="", $sqlstring="") {
/// Assumes that the input text (file or string consists of 
/// a number of SQL statements ENDING WITH SEMICOLONS.  The 
/// semicolons MUST be the last character in a line.
/// Lines that are blank or that start with "#" are ignored.
/// Only tested with mysql dump files (mysqldump -p -d moodle)

    global $CFG;

    $success = true;  // Let's be optimistic :-)

    if (!empty($sqlfile)) {
        if (!is_readable($sqlfile)) {
            $success = false;
            echo "<P>Tried to modify database, but \"$sqlfile\" doesn't exist!</P>";
            return $success;
        } else {
            $lines = file($sqlfile);
        }
    } else {
        $lines[] = $sqlstring;
    }

    $command = "";

    foreach ($lines as $line) {
        $line = rtrim($line);
        $length = strlen($line);

        if ($length and $line[0] <> "#") { 
            if (substr($line, $length-1, 1) == ";") {
                $line = substr($line, 0, $length-1);   // strip ;
                $command .= $line;
                $command = str_replace("prefix_", $CFG->prefix, $command); // Table prefixes
                if (! execute_sql($command)) {
                    $success = false;
                }
                $command = "";
            } else {
                $command .= $line;
            }
        }
    }

    return $success;

}

/// FUNCTIONS TO MODIFY TABLES ////////////////////////////////////////////

function table_column($table, $oldfield, $field, $type="integer", $size="10",
                      $signed="unsigned", $default="0", $null="not null", $after="") {
/// Add a new field to a table, or modify an existing one (if oldfield is defined).
    global $CFG, $db;

    switch (strtolower($CFG->dbtype)) {

        case "mysql":
        case "mysqlt":

            switch (strtolower($type)) {
                case "text":
                    $type = "TEXT";
                    $signed = "";
                    break;
                case "integer":
                    $type = "INTEGER($size)";
                    break;
                case "varchar":
                    $type = "VARCHAR($size)";
                    $signed = "";
                    break;
            }

            if (!empty($oldfield)) {
                $operation = "CHANGE $oldfield $field";
            } else {
                $operation = "ADD $field";
            }

            $default = "DEFAULT '$default'";

            if (!empty($after)) {
                $after = "AFTER `$after`";
            }

            execute_sql("ALTER TABLE {$CFG->prefix}$table $operation $type $signed $default $null $after");
            break;

        case "postgres7":        // From Petri Asikainen
            //Check db-version
            $dbinfo = $db->ServerInfo();
            $dbver = substr($dbinfo[version],0,3);
            
            $field = "$field";
            //to prevent conflicts with reserved words
            $oldfield = "\"$oldfield\"";

            switch (strtolower($type)) {
                case "integer":
                    if ($size <= 2) {
                        $type = "INT2";
                    } 
                    if ($size <= 4) {
                        $type = "INT";
                    }
                    if  ($size > 4) {
                        $type = "INT8";
                    }
                    break;
                case "varchar":
                    $type = "VARCHAR($size)";
                    break;
            }

            $default = "'$default'";

            //After is not implemented in postgesql
            //if (!empty($after)) {
            //    $after = "AFTER '$after'";
            //}

            if ($oldfield != "\"\"") {
                execute_sql("ALTER TABLE {$CFG->prefix}$table RENAME COLUMN $oldfield TO $field");
            } else {
                execute_sql("ALTER TABLE {$CFG->prefix}$table ADD COLUMN $field $type");
            }

            if ($dbver >= "7.3") {
                // modifying 'not null' is posible before 7.3
                //update default values to table
                if ($null == "NOT NULL") {
                    execute_sql("UPDATE {$CFG->prefix}$table SET $field=$default where $field IS NULL");
                    execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $null");
                } else {
                    execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field DROP NOT NULL");
                }
            }

            execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET DEFAULT $default");

            break;

        default:
            switch (strtolower($type)) {
                case "integer":
                    $type = "INTEGER";
                    break;
                case "varchar":
                    $type = "VARCHAR";
                    break;
            }

            $default = "DEFAULT '$default'";

            if (!empty($after)) {
                $after = "AFTER $after";
            }

            if (!empty($oldfield)) {
                execute_sql("ALTER TABLE {$CFG->prefix}$table RENAME COLUMN $oldfield $field");
            } else {
                execute_sql("ALTER TABLE {$CFG->prefix}$table ADD COLUMN $field $type");
            }

            execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $null");
            execute_sql("ALTER TABLE {$CFG->prefix}$table ALTER COLUMN $field SET $default");
            break;

    }
}


/// GENERIC FUNCTIONS TO CHECK AND COUNT RECORDS ////////////////////////////////////////

function record_exists($table, $field1="", $value1="", $field2="", $value2="", $field3="", $value3="") {
/// Returns true or false depending on whether the specified record exists

    global $CFG;

    if ($field1) {
        $select = "WHERE $field1 = '$value1'";
        if ($field2) {
            $select .= " AND $field2 = '$value2'";
            if ($field3) {
                $select .= " AND $field3 = '$value3'";
            }
        }
    } else {
        $select = "";
    }

    return record_exists_sql("SELECT * FROM $CFG->prefix$table $select LIMIT 1");
}


function record_exists_sql($sql) {
/// Returns true or false depending on whether the specified record exists
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute($sql);
    if (empty($rs)) return false;

    if ( $rs->RecordCount() ) {
        return true;
    } else {
        return false;
    }
}


function count_records($table, $field1="", $value1="", $field2="", $value2="", $field3="", $value3="") {
/// Get all the records and count them

    global $CFG;

    if ($field1) {
        $select = "WHERE $field1 = '$value1'";
        if ($field2) {
            $select .= " AND $field2 = '$value2'";
            if ($field3) {
                $select .= " AND $field3 = '$value3'";
            }
        }
    } else {
        $select = "";
    }

    return count_records_sql("SELECT COUNT(*) FROM $CFG->prefix$table $select");
}

function count_records_select($table, $select="") {
/// Get all the records and count them

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    return count_records_sql("SELECT COUNT(*) FROM $CFG->prefix$table $select");
}


function count_records_sql($sql) {
/// Get all the records and count them
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return 0;

    return $rs->fields[0];
}


/// GENERIC FUNCTIONS TO GET, INSERT, OR UPDATE DATA  ///////////////////////////////////

function get_record($table, $field1, $value1, $field2="", $value2="", $field3="", $value3="") {
/// Get a single record as an object

    global $CFG;

    $select = "WHERE $field1 = '$value1'";

    if ($field2) {
        $select .= " AND $field2 = '$value2'";
        if ($field3) {
            $select .= " AND $field3 = '$value3'";
        }
    }

    return get_record_sql("SELECT * FROM $CFG->prefix$table $select");
}

function get_record_sql($sql) {
/// Get a single record as an object
/// The sql statement is provided as a string.
/// A LIMIT is normally added to only look for 1 record

    global $db, $CFG;

    if ($CFG->debug > 7) {    // Debugging mode - don't use limit
       $limit = "";
    } else {
       $limit = " LIMIT 1";    // Workaround - limit to one record
    }

    if (!$rs = $db->Execute("$sql$limit")) {
        if ($CFG->debug > 7) {    // Debugging mode - print checks
            $db->debug=true;
            $db->Execute("$sql$limit");
            $db->debug=false;
        }
        return false;
    }

    if (!$recordcount = $rs->RecordCount()) {
        return false;                 // Found no records
    }

    if ($recordcount == 1) {          // Found one record
        return (object)$rs->fields;

    } else {                          // Error: found more than one record
        notify("Error:  Turn off debugging to hide this error.");
        notify("$sql$limit");
        if ($records = $rs->GetAssoc(true)) {
            notify("Found more than one record in get_record_sql !");
            print_object($records);
        } else {
            notify("Very strange error in get_record_sql !");
            print_object($rs);
        }
        print_continue("$CFG->wwwroot/admin/config.php");
    }
}

function get_record_select($table, $select="", $fields="*") {
/// Gets one record from a table, as an object
/// "select" is a fragment of SQL to define the selection criteria

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    return get_record_sql("SELECT $fields FROM $CFG->prefix$table $select");
}


function get_records($table, $field="", $value="", $sort="", $fields="*", $limitfrom="", $limitnum="") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// If "fields" is specified, only those fields are returned
/// The "key" is the first column returned, eg usually "id"
/// limitfrom and limitnum must both be specified or not at all

    global $CFG;

    if ($field) {
        $select = "WHERE $field = '$value'";
    } else {
        $select = "";
    }

    if ($limitfrom !== "") {
        switch ($CFG->dbtype) {
            case "mysql":
                 $limit = "LIMIT $limitfrom,$limitnum";
                 break;
            case "postgres7":
                 $limit = "LIMIT $limitnum OFFSET $limitfrom";
                 break;
            default: 
                 $limit = "LIMIT $limitnum,$limitfrom";
        }
    } else {
        $limit = "";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql("SELECT $fields FROM $CFG->prefix$table $select $sort $limit");
}

function get_records_select($table, $select="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// "select" is a fragment of SQL to define the selection criteria
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql("SELECT $fields FROM $CFG->prefix$table $select $sort");
}


function get_records_list($table, $field="", $values="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Differs from get_records() in that the values variable 
/// can be a comma-separated list of values eg  "4,5,6,10"
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($field) {
        $select = "WHERE $field in ($values)";
    } else {
        $select = "";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql("SELECT $fields FROM $CFG->prefix$table $select $sort");
}


function get_records_sql($sql) {
/// Get a number of records as an array of objects
/// The "key" is the first column returned, eg usually "id"
/// The sql statement is provided as a string.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() > 0 ) {
        if ($records = $rs->GetAssoc(true)) {
            foreach ($records as $key => $record) {
                $objects[$key] = (object) $record;
            }
            return $objects;
        } else {
            return false;
        }
    } else {
        return false;
    }
}

function get_records_menu($table, $field="", $value="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// If "fields" is specified, only those fields are returned
/// The "key" is the first column returned, eg usually "id"

    global $CFG;

    if ($field) {
        $select = "WHERE $field = '$value'";
    } else {
        $select = "";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql_menu("SELECT $fields FROM $CFG->prefix$table $select $sort");
}

function get_records_select_menu($table, $select="", $sort="", $fields="*") {
/// Get a number of records as an array of objects
/// Can optionally be sorted eg "time ASC" or "time DESC"
/// "select" is a fragment of SQL to define the selection criteria
/// Returns associative array of first two fields

    global $CFG;

    if ($select) {
        $select = "WHERE $select";
    }

    if ($sort) {
        $sort = "ORDER BY $sort";
    }

    return get_records_sql_menu("SELECT $fields FROM $CFG->prefix$table $select $sort");
}


function get_records_sql_menu($sql) {
/// Given an SQL select, this function returns an associative 
/// array of the first two columns.  This is most useful in 
/// combination with the choose_from_menu function to create 
/// a form menu.

    global $db;

    $rs = $db->Execute("$sql");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() > 0 ) {
        while (!$rs->EOF) {
            $menu[$rs->fields[0]] = $rs->fields[1];
            $rs->MoveNext();
        }
        return $menu;
        
    } else {
        return false;
    }
}

function get_field($table, $return, $field1, $value1, $field2="", $value2="", $field3="", $value3="") {
/// Get a single field from a database record

    global $db, $CFG;

    $select = "WHERE $field1 = '$value1'";

    if ($field2) {
        $select .= " AND $field2 = '$value2'";
        if ($field3) {
            $select .= " AND $field3 = '$value3'";
        }
    }

    $rs = $db->Execute("SELECT $return FROM $CFG->prefix$table $select");
    if (empty($rs)) return false;

    if ( $rs->RecordCount() == 1 ) {
        return $rs->fields["$return"];
    } else {
        return false;
    }
}

function set_field($table, $newfield, $newvalue, $field1, $value1, $field2="", $value2="", $field3="", $value3="") {
/// Set a single field in a database record

    global $db, $CFG;

    $select = "WHERE $field1 = '$value1'";

    if ($field2) {
        $select .= " AND $field2 = '$value2'";
        if ($field3) {
            $select .= " AND $field3 = '$value3'";
        }
    }

    return $db->Execute("UPDATE $CFG->prefix$table SET $newfield = '$newvalue' $select");
}


function delete_records($table, $field1="", $value1="", $field2="", $value2="", $field3="", $value3="") {
/// Delete one or more records from a table

    global $db, $CFG;

    if ($field1) {
        $select = "WHERE $field1 = '$value1'";
        if ($field2) {
            $select .= " AND $field2 = '$value2'";
            if ($field3) {
                $select .= " AND $field3 = '$value3'";
            }
        }
    } else {
        $select = "";
    }

    return $db->Execute("DELETE FROM $CFG->prefix$table $select");
}

function delete_records_select($table, $select="") {
/// Delete one or more records from a table
/// "select" is a fragment of SQL to define the selection criteria

    global $CFG, $db;

    if ($select) {
        $select = "WHERE $select";
    }

    return $db->Execute("DELETE FROM $CFG->prefix$table $select");
}


function insert_record($table, $dataobject, $returnid=true) {
/// Insert a record into a table and return the "id" field if required
/// If the return ID isn't required, then this just reports success as true/false.
/// $dataobject is an object containing needed data

    global $db, $CFG;

    // Determine all the fields needed
    if (! $columns = $db->MetaColumns("$CFG->prefix$table")) {
        return false;
    }
    $data = (array)$dataobject;

    // Pull out data from the dataobject that matches the fields in the table.
    // If fields are missing or empty, then try to set the defaults explicitly
    // because some databases (eg PostgreSQL) don't always set them properly
    foreach ($columns as $column) {
        if(isset($column->primary_key) and $column->primary_key == 1) {
            $pkey = $column->name; // take column name of primary key
        }    
        if ($column->name <> "id") {
            if (isset($data[$column->name])) { 
                if ((string)$data[$column->name] == "" and !empty($column->has_default) and !empty($column->default_value)) {
                    $ddd[$column->name] = $column->default_value;
                } else {
                    $ddd[$column->name] = $data[$column->name];
                }
            } else {
                if (!empty($column->has_default) and !empty($column->default_value)) {
                    $ddd[$column->name] = $column->default_value;
                } 
            }
        }
    }


    // Construct SQL queries
    if (! $numddd = count($ddd)) {
        return false;
    }

    $count = 0;
    $inscolumns = "";
    $insvalues = "";
    $select = "";

    foreach ($ddd as $key => $value) {
        if (!is_null($value)){
            if ($select) {
                $inscolumns .= ", ";
                $insvalues .= ", ";
                $select .= " AND ";
            }
            $inscolumns .= "$key";
            $insvalues .= "'$value'";
            $select .= "$key = '$value'";
        }
    }

    if (! $rs = $db->Execute("INSERT INTO $CFG->prefix$table ($inscolumns) VALUES ($insvalues)")) {
        return false;
    }

    if ($returnid) {
        if ($CFG->dbtype == "mysql" ) { 
            return $db->Insert_ID();   // ADOdb has stored the ID for us, but it isn't reliable
        }
        
        if ($CFG->dbtype == "postgres7" and isset($pkey)){
            $oid = $db->Insert_ID();
            if ($rs = $db->Execute("SELECT $pkey FROM $CFG->prefix$table WHERE oid = $oid")) {
                if ($rs->RecordCount() == 1) {
                    return $rs->fields[0];
                } else {
                    return false;
                }
            }
        }    
        // Try to pull the record out again to find the id.  This is the most cross-platform method.
        if ($rs = $db->Execute("SELECT id FROM $CFG->prefix$table WHERE $select")) {
            if ($rs->RecordCount() == 1) {
                return $rs->fields[0];
            }
        }

        return false;

    } else {
        return true;
    }
}


function update_record($table, $dataobject) {
/// Update a record in a table
/// $dataobject is an object containing needed data
/// Relies on $dataobject having a variable "id" to 
/// specify the record to update

    global $db, $CFG;

    if (! isset($dataobject->id) ) {
        return false;
    }

    // Determine all the fields in the table
    if (!$columns = $db->MetaColumns("$CFG->prefix$table")) {
        return false;
    }
    $data = (array)$dataobject;

    // Pull out data matching these fields
    foreach ($columns as $column) {
        if ($column->name <> "id" and isset($data[$column->name]) ) {
            $ddd[$column->name] = $data[$column->name];
        }
    }

    // Construct SQL queries
    $numddd = count($ddd);
    $count = 0;
    $update = "";

    foreach ($ddd as $key => $value) {
        $count++;
        $update .= "$key = '$value'";
        if ($count < $numddd) {
            $update .= ", ";
        }
    }

    if ($rs = $db->Execute("UPDATE $CFG->prefix$table SET $update WHERE id = '$dataobject->id'")) {
        return true;
    } else {
        return false;
    }
}


/// USER DATABASE ////////////////////////////////////////////////

function get_user_info_from_db($field, $value) {
/// Get a complete user record, which includes all the info 
/// in the user record, as well as membership information
/// Suitable for setting as $USER session cookie.

    if (!$field or !$value) {
        return false;
    }

    if (! $user = get_record_select("user", "$field = '$value' AND deleted <> '1'")) {
        return false;
    }

    // Add membership information

    if ($site = get_site()) { // Everyone is always a member of the top course
        $user->student[$site->id] = true;
    }

    if ($students = get_records("user_students", "userid", $user->id)) {
        foreach ($students as $student) {
            if (get_field("course", "visible", "id", $student->course)) {
                $user->student[$student->course] = true;
                $user->zoom[$student->course] = $student->zoom;
            }
        }
    }

    if ($teachers = get_records("user_teachers", "userid", $user->id)) {
        foreach ($teachers as $teacher) {
            $user->teacher[$teacher->course] = true;
            if ($teacher->editall) {
                $user->teacheredit[$teacher->course] = true;
            }
        }
    }

    if ($admins = get_records("user_admins", "userid", $user->id)) {
        foreach ($admins as $admin) {
            $user->admin = true;
            break;
        }
    }

    if ($displays = get_records("course_display", "userid", $user->id)) {
        foreach ($displays as $display) {
            $user->display[$display->course] = $display->display;
        }
    }

    return $user;
}

function update_user_in_db() {
/// Updates user record to record their last access

   global $db, $USER, $REMOTE_ADDR, $CFG;

   if (!isset($USER->id)) 
       return false;

   $timenow = time();
   if ($db->Execute("UPDATE {$CFG->prefix}user SET lastIP='$REMOTE_ADDR', lastaccess='$timenow' 
                     WHERE id = '$USER->id' ")) {
       return true;
   } else {
       return false;
   }
}


function adminlogin($username, $md5password) {
/// Does this username and password specify a valid admin user?

    global $CFG;

    return record_exists_sql("SELECT u.id 
                                FROM {$CFG->prefix}user u, 
                                     {$CFG->prefix}user_admins a 
                              WHERE u.id = a.userid 
                                AND u.username = '$username' 
                                AND u.password = '$md5password'");
}


function get_guest() {
    return get_user_info_from_db("username", "guest");
}


function get_admin () {
/// Returns $user object of the main admin user

    global $CFG;

    if ( $admins = get_admins() ) {
        foreach ($admins as $admin) {
            return $admin;   // ie the first one 
        }
    } else {
        return false;
    }
}

function get_admins() {
/// Returns list of all admins

    global $CFG;

    return get_records_sql("SELECT u.* 
                              FROM {$CFG->prefix}user u, 
                                   {$CFG->prefix}user_admins a
                             WHERE a.userid = u.id
                             ORDER BY u.id ASC");
}

function get_creators() {
/// Returns list of all admins

    global $CFG;

    return get_records_sql("SELECT u.*
                              FROM {$CFG->prefix}user u,
                                   {$CFG->prefix}user_coursecreators a
                             WHERE a.userid = u.id
                             ORDER BY u.id ASC");
}

function get_teacher($courseid) {
/// Returns $user object of the main teacher for a course

    global $CFG;

    if ( $teachers = get_course_teachers($courseid, "t.authority ASC")) {
        foreach ($teachers as $teacher) {
            if ($teacher->authority) {
                return $teacher;   // the highest authority teacher
            }
        }
    } else {
        return false;
    }
}

function get_recent_enrolments($courseid, $timestart) {
/// Searches logs to find all enrolments since a certain date
/// and returns the data (used to print recent activity)

    global $CFG;

    return get_records_sql("SELECT u.id, u.firstname, u.lastname
                            FROM {$CFG->prefix}user u,
                                 {$CFG->prefix}user_students s,
                                 {$CFG->prefix}log l
                            WHERE l.time > '$timestart' 
                              AND l.course = '$courseid'
                              AND l.module = 'course' 
                              AND l.action = 'enrol'
                              AND l.info = u.id
                              AND u.id = s.userid
                              AND s.course = '$courseid'
                              GROUP BY l.info
                              ORDER BY l.time ASC");
}

function get_course_students($courseid, $sort="u.lastaccess DESC") {
/// Returns list of all students in this course
/// if courseid = 0 then return ALL students in all courses

    global $CFG;

    return get_records_sql("SELECT u.id, u.username, u.firstname, u.lastname, u.maildisplay, u.mailformat,
                            u.email, u.city, u.country, u.lastaccess, u.lastlogin, u.picture
                            FROM {$CFG->prefix}user u, 
                                 {$CFG->prefix}user_students s
                            WHERE s.course = '$courseid' AND s.userid = u.id AND u.deleted = '0'
                            ORDER BY $sort");
}

function get_course_teachers($courseid, $sort="t.authority ASC") {
/// Returns list of all teachers in this course
/// if courseid = 0 then return ALL teachers in all courses

    global $CFG;

    return get_records_sql("SELECT u.*,t.authority,t.role,t.editall
                            FROM {$CFG->prefix}user u, 
                                 {$CFG->prefix}user_teachers t
                            WHERE t.course = '$courseid' AND t.userid = u.id AND u.deleted = '0'
                            ORDER BY $sort");
}

function get_course_users($courseid, $sort="u.lastaccess DESC") {
/// Returns all the users of a course: students and teachers
/// If the "course" is actually the site, then return all site users.

    $site = get_site();

    if ($courseid == $site->id) {
        return get_site_users($sort);
    }

    /// Using this method because the single SQL just would not always work!

    $teachers = get_course_teachers($courseid, $sort);
    $students = get_course_students($courseid, $sort);

    if ($teachers and $students) {
        return array_merge($teachers, $students);
    } else if ($teachers) {
        return $teachers;
    } else {
        return $students;
    }

    /// Why wouldn't this work?
    ///    return get_records_sql("SELECT u.* FROM user u, user_students s, user_teachers t
    ///                            WHERE (s.course = '$courseid' AND s.userid = u.id) OR 
    ///                                  (t.course = '$courseid' AND t.userid = u.id)
    ///                            ORDER BY $sort");
}

function get_site_users($sort="u.lastaccess DESC") {
/// Returns a list of all active users who are enrolled 
/// or teaching in courses on this server

    global $CFG, $db;

    //$db->debug = true;

    return get_records_sql("SELECT u.id, u.username, u.firstname, u.lastname, u.maildisplay, u.mailformat,
                                   u.email, u.city, u.country, u.lastaccess, u.lastlogin, u.picture
                              FROM {$CFG->prefix}user u, 
                                   {$CFG->prefix}user_students s, 
                                   {$CFG->prefix}user_teachers t,
                                   {$CFG->prefix}user_coursecreators c,
                                   {$CFG->prefix}user_admins a
                             WHERE s.userid = u.id 
                                OR t.userid = u.id
                                OR a.userid = u.id
                                OR c.userid = u.id
                             GROUP BY u.id 
                             ORDER BY $sort ");
}


function get_users($get=true, $search="", $confirmed=false, $exceptions="", $sort="firstname ASC") {
/// Returns a subset of users, 
/// $get - if false then only a count of the records is returned
/// $search is a simple string to search for
/// $confirmed is a switch to allow/disallow unconfirmed users
/// $exceptions is a list of IDs to ignore, eg 2,4,5,8,9,10
/// $sort is a sorting criteria to use

    if ($search) {
        $search = " AND (firstname LIKE '%$search%'
                     OR lastname LIKE '%$search%'
                     OR email LIKE '%$search%') ";
    }

    if ($confirmed) {
        $confirmed = " AND confirmed = '1' ";
    }

    if ($exceptions) {
        $exceptions = " AND id NOT IN ($exceptions) ";
    }

    if ($sort and $get) {
        $sort = " ORDER BY $sort ";
    } else {
        $sort = "";
    }

    if ($get) {
        return get_records_select("user", "username <> 'guest' AND deleted = 0 $search $confirmed $exceptions $sort");
    } else {
        return count_records_select("user", "username <> 'guest' AND deleted = 0 $search $confirmed $exceptions $sort");
    }
}


function get_users_listing($sort, $dir="ASC", $page=1, $recordsperpage=20, $search="") {
    global $CFG;

    switch ($CFG->dbtype) {
        case "mysql":
             $limit = "LIMIT $page,$recordsperpage";
             break;
        case "postgres7":
             $limit = "LIMIT $recordsperpage OFFSET ".($page);
             break;
        default: 
             $limit = "LIMIT $recordsperpage,$page";
    }

    if ($search) {
        $search = " AND (firstname LIKE '%$search%'
                     OR lastname LIKE '%$search%'
                     OR email LIKE '%$search%') ";
    }

    return get_records_sql("SELECT id, username, email, firstname, lastname, city, country, lastaccess  
                              FROM {$CFG->prefix}user 
                             WHERE username <> 'guest' 
                               AND deleted <> '1' $search
                          ORDER BY $sort $dir $limit");

}

function get_users_confirmed() {
    global $CFG;
    return get_records_sql("SELECT * 
                              FROM {$CFG->prefix}user 
                             WHERE confirmed = 1 
                               AND deleted = 0
                               AND username <> 'guest' 
                               AND username <> 'changeme'");
}


function get_users_unconfirmed($cutofftime=2000000000) {
    global $CFG;
    return get_records_sql("SELECT * 
                             FROM {$CFG->prefix}user 
                            WHERE confirmed = 0
                              AND firstaccess > 0 
                              AND firstaccess < '$cutofftime'");
}


function get_users_longtimenosee($cutofftime) {
    global $CFG;

    $db->debug = true;
    return get_records_sql("SELECT u.* 
                              FROM {$CFG->prefix}user u, 
                                   {$CFG->prefix}user_students s
                             WHERE u.lastaccess > '0' 
                               AND u.lastaccess < '$cutofftime' 
                               AND u.id = s.userid
                          GROUP BY u.id");
}


/// OTHER SITE AND COURSE FUNCTIONS /////////////////////////////////////////////


function get_site () {
/// Returns $course object of the top-level site.

    if ( $course = get_record("course", "category", 0)) {
        return $course;
    } else {
        return false;
    }
}


function get_courses($categoryid="all", $sort="sortorder ASC", $fields="*") {
/// Returns list of courses, for whole site, or category

    if ($categoryid == "all") {
        $courses = get_records("course", "", "", $sort, $fields);
    } else {
        $courses = get_records("course", "category", "$categoryid", $sort, $fields);
    }

    if ($courses) {  /// Remove unavailable courses from the list
        foreach ($courses as $key => $course) {
            if (!$course->visible) {
                if (!isteacher($course->id)) {
                    unset($courses[$key]);
                }
            }
        }
    }
    return $courses;
}


function get_my_courses($userid, $sort="c.fullname ASC") {
    global $CFG;

    return get_records_sql("SELECT c.* 
                              FROM {$CFG->prefix}course c, 
                                   {$CFG->prefix}user_students s, 
                                   {$CFG->prefix}user_teachers t 
                             WHERE (s.userid = '$userid' AND s.course = c.id)
                                OR (t.userid = '$userid' AND t.course = c.id)
                             GROUP BY c.id 
                             ORDER BY $sort");
}


function get_courses_search($search, $sort="fullname ASC", $page=0, $recordsperpage=50) {
/// Returns a list of courses that match a search

    global $CFG;

    switch ($CFG->dbtype) {
        case "mysql":
             $limit = "LIMIT $page,$recordsperpage";
             break;
        case "postgres7":
             $limit = "LIMIT $recordsperpage OFFSET ".($page * $recordsperpage);
             break;
        default: 
             $limit = "LIMIT $recordsperpage,$page";
    }

    //to allow caseinsensitive search for postgesql
    if ($CFG->dbtype == "postgres7") {
       $LIKE = "ILIKE";
    } else {
       $LIKE = "LIKE";
    }

    $fullnamesearch = "";
    $summarysearch = "";

    $searchterms = explode(" ", $search);     // Search for words independently

    foreach ($searchterms as $searchterm) {
        if ($fullnamesearch) {
            $fullnamesearch .= " AND ";
        }
        $fullnamesearch .= " fullname $LIKE '%$searchterm%' ";

        if ($summarysearch) {
            $summarysearch .= " AND ";
        }
        $summarysearch .= " summary $LIKE '%$searchterm%' ";
    }


    $courses = get_records_sql("SELECT * 
                                  FROM {$CFG->prefix}course
                                 WHERE ($fullnamesearch OR $summarysearch)
                              ORDER BY $sort $limit");

    if ($courses) {  /// Remove unavailable courses from the list
        foreach ($courses as $key => $course) {
            if (!$course->visible) {
                if (!isteacher($course->id)) {
                    unset($courses[$key]);
                }
            }
        }
    }

    return $courses;
}


function get_categories($parent="none", $sort="sortorder ASC") {
/// Returns a sorted list of categories

    if ($parent == "none") {
        $categories = get_records("course_categories", "", "", $sort);
    } else {
        $categories = get_records("course_categories", "parent", $parent, $sort);
    }
    if ($categories) {  /// Remove unavailable categories from the list
        $admin = isadmin();
        foreach ($categories as $key => $category) {
            if (!$category->visible) {
                if (!$admin) {
                    unset($categories[$key]);
                }
            }
        }
    }
    return $categories;
}


function fix_course_sortorder($categoryid, $sort="sortorder ASC") {
/// Given a category object, this function makes sure the courseorder 
/// variable reflects the real world.

    if (!$courses = get_records("course", "category", "$categoryid", "$sort", "id, sortorder")) {
        return true;
    }

    $count = 0;
    $modified = false;

    foreach ($courses as $course) {
        if ($course->sortorder != $count) {
            set_field("course", "sortorder", $count, "id", $course->id);
            $modified = true;
        }
        $count++;
    }

    if ($modified) {
        set_field("course_categories", "timemodified", time(), "id", $categoryid);
    }

    return true;
}

function make_default_scale() {
/// This function creates a default separated/connected scale
/// so there's something in the database.  The locations of 
/// strings and files is a bit odd, but this is because we 
/// need to maintain backward compatibility with many different
/// existing language translations and older sites.

    global $CFG;

    $defaultscale = NULL;
    $defaultscale->courseid = 0;
    $defaultscale->userid = 0;
    $defaultscale->name  = get_string("separateandconnected");
    $defaultscale->scale = get_string("postrating1", "forum").",".
                           get_string("postrating2", "forum").",".
                           get_string("postrating3", "forum");
    $defaultscale->timemodified = time();

    /// Read in the big description from the file.  Note this is not 
    /// HTML (despite the file extension) but Moodle format text.
    $parentlang = get_string("parentlang");
    if (is_readable("$CFG->dirroot/lang/$CFG->lang/help/forum/ratings.html")) {
        $file = file("$CFG->dirroot/lang/$CFG->lang/help/forum/ratings.html");
    } else if ($parentlang and is_readable("$CFG->dirroot/lang/$parentlang/help/forum/ratings.html")) {
        $file = file("$CFG->dirroot/lang/$parentlang/help/forum/ratings.html");
    } else if (is_readable("$CFG->dirroot/lang/en/help/forum/ratings.html")) {
        $file = file("$CFG->dirroot/lang/en/help/forum/ratings.html");
    } else {
        $file = "";
    }

    $defaultscale->description = addslashes(implode("", $file));

    if ($defaultscale->id = insert_record("scale", $defaultscale)) {
        execute_sql("UPDATE {$CFG->prefix}forum SET scale = '$defaultscale->id'");
    }
}

function get_scales_menu($courseid=0) {
/// Returns a menu of all available scales
/// from the site as well as the given course

    global $CFG;
    
    $sql = "SELECT id, name FROM {$CFG->prefix}scale 
             WHERE courseid = '0' or courseid = '$courseid' 
          ORDER BY courseid ASC, name ASC";

    if ($scales = get_records_sql_menu("$sql")) {
        return $scales;
    }

    make_default_scale();

    return get_records_sql_menu("$sql");
}

/// MODULE FUNCTIONS /////////////////////////////////////////////////

function get_course_mods($courseid) {
/// Just gets a raw list of all modules in a course
    global $CFG;

    return get_records_sql("SELECT cm.*, m.name as modname
                            FROM {$CFG->prefix}modules m, 
                                 {$CFG->prefix}course_modules cm
                            WHERE cm.course = '$courseid' 
                            AND cm.deleted = '0'
                            AND cm.module = m.id ");
}

function get_coursemodule_from_instance($modulename, $instance, $courseid) {
/// Given an instance of a module, finds the coursemodule description

    global $CFG;

    return get_record_sql("SELECT cm.*, m.name
                           FROM {$CFG->prefix}course_modules cm, 
                                {$CFG->prefix}modules md, 
                                {$CFG->prefix}$modulename m 
                           WHERE cm.course = '$courseid' AND 
                                 cm.deleted = '0' AND
                                 cm.instance = m.id AND 
                                 md.name = '$modulename' AND 
                                 md.id = cm.module AND
                                 m.id = '$instance'");

}

function get_all_instances_in_course($modulename, $course) {
/// Returns an array of all the active instances of a particular
/// module in a given course, sorted in the order they are defined
/// in the course.   Returns false on any errors.
/// $course is a course object, this depends on an accurate $course->modinfo

    global $CFG;

    if (!$modinfo = unserialize($course->modinfo)) {
        return array();
    }

    if (!$rawmods = get_records_sql("SELECT cm.id as coursemodule, m.*,cw.section,cm.visible as visible 
                            FROM {$CFG->prefix}course_modules cm, 
                                 {$CFG->prefix}course_sections cw, 
                                 {$CFG->prefix}modules md, 
                                 {$CFG->prefix}$modulename m 
                            WHERE cm.course = '$course->id' AND 
                                  cm.instance = m.id AND 
                                  cm.deleted = '0' AND
                                  cm.section = cw.id AND 
                                  md.name = '$modulename' AND 
                                  md.id = cm.module")) {
        return array();
    }

    // Hide non-visible instances from students
    if (isteacher($course->id)) {
        $invisible = -1;
    } else {
        $invisible = 0;
    }

    foreach ($modinfo as $mod) {
        if ($mod->mod == $modulename and $mod->visible > $invisible) {
            $outputarray[] = $rawmods[$mod->cm];
        }
    }

    return $outputarray;

}


function instance_is_visible($moduletype, $module) {
/// Given a valid module object with info about the id and course, 
/// and the module's type (eg "forum") returns whether the object 
/// is visible or not

    global $CFG;

    if ($records = get_records_sql("SELECT cm.instance, cm.visible
                                    FROM {$CFG->prefix}course_modules cm,
                                         {$CFG->prefix}modules m
                                   WHERE cm.course = '$module->course' AND
                                         cm.module = m.id AND 
                                         m.name = '$moduletype' AND 
                                         cm.instance = '$module->id'")) { 

        foreach ($records as $record) { // there should only be one - use the first one
            return $record->visible;
        }
    }

    return true;  // visible by default!
}


/// LOG FUNCTIONS /////////////////////////////////////////////////////


function add_to_log($course, $module, $action, $url="", $info="") {
/// Add an entry to the log table.  These are "action" focussed rather
/// than web server hits, and provide a way to easily reconstruct what 
/// any particular student has been doing.
///
/// course = the course id
/// module = forum, journal, resource, course, user etc
/// action = view, edit, post (often but not always the same as the file.php)
/// url    = the file and parameters used to see the results of the action
/// info   = additional description information 

    global $db, $CFG, $USER, $REMOTE_ADDR;

    if (isset($USER->realuser)) {  // Don't log
        return;
    }

    $userid = empty($USER->id) ? "" : $USER->id;

    $timenow = time();
    $info = addslashes($info);

    $result = $db->Execute("INSERT INTO {$CFG->prefix}log (time,
                                        userid,
                                        course,
                                        ip,
                                        module,
                                        action,
                                        url,
                                        info)
                             VALUES ('$timenow',
                                        '$userid',
                                        '$course',
                                        '$REMOTE_ADDR',
                                        '$module',
                                        '$action',
                                        '$url',
                                        '$info')");

    if (!$result and ($CFG->debug > 7)) {
        echo "<P>Error: Could not insert a new entry to the Moodle log</P>";  // Don't throw an error
    }    
}


function get_logs($select, $order) {
    global $CFG;

    return get_records_sql("SELECT l.*, u.firstname, u.lastname, u.picture 
                              FROM {$CFG->prefix}log l, 
                                   {$CFG->prefix}user u 
                                   $select $order");
}

function get_logs_usercourse($userid, $courseid, $coursestart) {
    global $CFG;

    if ($courseid) {
       $courseselect = " AND course = '$courseid' ";
    }

    return get_records_sql("SELECT floor((`time` - $coursestart)/86400) as day, count(*) as num 
                            FROM {$CFG->prefix}log 
                           WHERE userid = '$userid' 
                             AND `time` > '$coursestart' $courseselect
                        GROUP BY day ");
}

function get_logs_userday($userid, $courseid, $daystart) {
    global $CFG;

    if ($courseid) {
       $courseselect = " AND course = '$courseid' ";
    }

    return get_records_sql("SELECT floor((`time` - $daystart)/3600) as hour, count(*) as num
                            FROM {$CFG->prefix}log
                           WHERE userid = '$userid' 
                             AND `time` > '$daystart' $courseselect
                        GROUP BY hour ");
}

/// GENERAL HELPFUL THINGS  ///////////////////////////////////

function print_object($object) {
/// Mostly just for debugging

    echo "<PRE>";
    print_r($object);
    echo "</PRE>";
}


// vim:autoindent:expandtab:shiftwidth=4:tabstop=4:tw=140:
?>