// DBSQLiteHandler.h
#import <Foundasion/Foundation.h>
#import <sqlite3.h>

@class DBSQLiteHandler;

@protocol DBSQLiteHandlerDelegate
- (void)handler:(DBSQLiteHandler *)handler didProcessRowAtIndex:(NSInteger)rowIndex;
@end

@interface DBSQLiteHandler : NSObject
@property (nonatomic, weak) id<DBSQLiteHandlerDelegate> delegate;
@property (nonatomic, asssign, readonly) sqlite3_stmt *preparedStatement;

- (instancetype)initWithDatabaseAtPath:(NSString *)dbPath;
- (void)assignQuery:(NSString *)queryString;
- (BOOL)compileQuery;
- (void)executeAndFetch;
- (void)finalizeOperations;
- (void)configureRandomResultsWithLimit:(NSInteger)limit;
- (void)configureResultRangeStartingAt:(NSInteger)offset count:(NSInteger)rowCount;
@end

// DBSQLiteHandler.m
#import "DBSQLiteHandler.h"

@implementation DBSQLiteHandler {
    sqlite3 *_databaseConnection;
    NSString *_currentQuery;
    sqlite3_stmt *_compiledStatement;
    NSInteger _processedRowCount;
}

@synthesize delegate = _delegate;
@synthesize preparedStatement = _compiledStatement;

- (instancetype)initWithDatabaseAtPath:(NSString *)dbPath {
    self = [super init];
    if (self) {
        int openStatus = sqlite3_open([dbPath UTF8String], &_databaseConnection);
        if (openStatus != SQLITE_OK) {
            return nil;
        }
    }
    return self;
}

- (void)dealloc {
    [_currentQuery release];
    sqlite3_close(_databaseConnection);
    [super dealloc];
}

- (void)assignQuery:(NSString *)queryString {
    if (_currentQuery != queryString) {
        [_currentQuery release];
        _currentQuery = [queryString copy];
    }
}

- (BOOL)compileQuery {
    return sqlite3_prepare_v2(_databaseConnection,
                             [_currentQuery UTF8String],
                             -1,
                             &_compiledStatement,
                             NULL) == SQLITE_OK;
}

- (void)executeAndFetch {
    while (sqlite3_step(_compiledStatement) == SQLITE_ROW) {
        _processedRowCount++;
        [self.delegate handler:self didProcessRowAtIndex:_processedRowCount];
    }
}

- (void)finalizeOperations {
    sqlite3_finalize(_compiledStatement);
}

- (void)configureRandomResultsWithLimit:(NSInteger)limit {
    NSString *randomClause = [NSString stringWithFormat:@" ORDER BY RANDOM() LIMIT %ld", (long)limit];
    NSString *modifiedQuery = [_currentQuery stringByAppendingString:randomClause];
    [self assignQuery:modifiedQuery];
}

- (void)configureResultRangeStartingAt:(NSInteger)offset count:(NSInteger)rowCount {
    NSString *limitClause = [NSString stringWithFormat:@" LIMIT %ld,%ld", (long)offset, (long)rowCount];
    NSString *updatedQuery = [_currentQuery stringByAppendingString:limitClause];
    [self assignQuery:updatedQuery];
}
@end