// Software License Agreement (BSD License)
//
// Copyright (c) 2010-2016, Deusty, LLC
// All rights reserved.
//
// Redistribution and use of this software in source and binary forms,
// with or without modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// * Neither the name of Deusty nor the names of its contributors may be used
//   to endorse or promote products derived from this software without specific
//   prior written permission of Deusty, LLC.

#import "AWSDDAbstractDatabaseLogger.h"
#import <math.h>


#if !__has_feature(objc_arc)
#error This file must be compiled with ARC. Use -fobjc-arc flag (or convert project to ARC).
#endif

@interface AWSDDAbstractDatabaseLogger ()

- (void)destroySaveTimer;
- (void)destroyDeleteTimer;

@end

#pragma mark -

@implementation AWSDDAbstractDatabaseLogger

- (instancetype)init {
    if ((self = [super init])) {
        _saveThreshold = 500;
        _saveInterval = 60;           // 60 seconds
        _maxAge = (60 * 60 * 24 * 7); //  7 days
        _deleteInterval = (60 * 5);   //  5 minutes
    }

    return self;
}

- (void)dealloc {
    [self destroySaveTimer];
    [self destroyDeleteTimer];
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Override Me
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (BOOL)db_log:(AWSDDLogMessage *)logMessage {
    // Override me and add your implementation.
    //
    // Return YES if an item was added to the buffer.
    // Return NO if the logMessage was ignored.

    return NO;
}

- (void)db_save {
    // Override me and add your implementation.
}

- (void)db_delete {
    // Override me and add your implementation.
}

- (void)db_saveAndDelete {
    // Override me and add your implementation.
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Private API
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (void)performSaveAndSuspendSaveTimer {
    if (_unsavedCount > 0) {
        if (_deleteOnEverySave) {
            [self db_saveAndDelete];
        } else {
            [self db_save];
        }
    }

    _unsavedCount = 0;
    _unsavedTime = 0;

    if (_saveTimer && !_saveTimerSuspended) {
        dispatch_suspend(_saveTimer);
        _saveTimerSuspended = YES;
    }
}

- (void)performDelete {
    if (_maxAge > 0.0) {
        [self db_delete];

        _lastDeleteTime = dispatch_time(DISPATCH_TIME_NOW, 0);
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Timers
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (void)destroySaveTimer {
    if (_saveTimer) {
        dispatch_source_cancel(_saveTimer);

        if (_saveTimerSuspended) {
            // Must resume a timer before releasing it (or it will crash)
            dispatch_resume(_saveTimer);
            _saveTimerSuspended = NO;
        }

        #if !OS_OBJECT_USE_OBJC
        dispatch_release(_saveTimer);
        #endif
        _saveTimer = NULL;
    }
}

- (void)updateAndResumeSaveTimer {
    if ((_saveTimer != NULL) && (_saveInterval > 0.0) && (_unsavedTime > 0.0)) {
        uint64_t interval = (uint64_t)(_saveInterval * (NSTimeInterval) NSEC_PER_SEC);
        dispatch_time_t startTime = dispatch_time(_unsavedTime, interval);

        dispatch_source_set_timer(_saveTimer, startTime, interval, 1ull * NSEC_PER_SEC);

        if (_saveTimerSuspended) {
            dispatch_resume(_saveTimer);
            _saveTimerSuspended = NO;
        }
    }
}

- (void)createSuspendedSaveTimer {
    if ((_saveTimer == NULL) && (_saveInterval > 0.0)) {
        _saveTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, self.loggerQueue);

        dispatch_source_set_event_handler(_saveTimer, ^{ @autoreleasepool {
                                                            [self performSaveAndSuspendSaveTimer];
                                                        } });

        _saveTimerSuspended = YES;
    }
}

- (void)destroyDeleteTimer {
    if (_deleteTimer) {
        dispatch_source_cancel(_deleteTimer);
        #if !OS_OBJECT_USE_OBJC
        dispatch_release(_deleteTimer);
        #endif
        _deleteTimer = NULL;
    }
}

- (void)updateDeleteTimer {
    if ((_deleteTimer != NULL) && (_deleteInterval > 0.0) && (_maxAge > 0.0)) {
        uint64_t interval = (uint64_t)(_deleteInterval * (NSTimeInterval) NSEC_PER_SEC);
        dispatch_time_t startTime;

        if (_lastDeleteTime > 0) {
            startTime = dispatch_time(_lastDeleteTime, interval);
        } else {
            startTime = dispatch_time(DISPATCH_TIME_NOW, interval);
        }

        dispatch_source_set_timer(_deleteTimer, startTime, interval, 1ull * NSEC_PER_SEC);
    }
}

- (void)createAndStartDeleteTimer {
    if ((_deleteTimer == NULL) && (_deleteInterval > 0.0) && (_maxAge > 0.0)) {
        _deleteTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, self.loggerQueue);

        if (_deleteTimer != NULL) {
            dispatch_source_set_event_handler(_deleteTimer, ^{ @autoreleasepool {
                                                                  [self performDelete];
                                                              } });

            [self updateDeleteTimer];

            if (_deleteTimer != NULL) {
                dispatch_resume(_deleteTimer);
            }
        }
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Configuration
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (NSUInteger)saveThreshold {
    // The design of this method is taken from the AWSDDAbstractLogger implementation.
    // For extensive documentation please refer to the AWSDDAbstractLogger implementation.

    // Note: The internal implementation MUST access the colorsEnabled variable directly,
    // This method is designed explicitly for external access.
    //
    // Using "self." syntax to go through this method will cause immediate deadlock.
    // This is the intended result. Fix it by accessing the ivar directly.
    // Great strides have been take to ensure this is safe to do. Plus it's MUCH faster.

    NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");
    NSAssert(![self isOnInternalLoggerQueue], @"MUST access ivar directly, NOT via self.* syntax.");

    dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];

    __block NSUInteger result;

    dispatch_sync(globalLoggingQueue, ^{
        dispatch_sync(self.loggerQueue, ^{
            result = self->_saveThreshold;
        });
    });

    return result;
}

- (void)setSaveThreshold:(NSUInteger)threshold {
    dispatch_block_t block = ^{
        @autoreleasepool {
            if (self->_saveThreshold != threshold) {
                self->_saveThreshold = threshold;

                // Since the saveThreshold has changed,
                // we check to see if the current unsavedCount has surpassed the new threshold.
                //
                // If it has, we immediately save the log.

                if ((self->_unsavedCount >= self->_saveThreshold) && (self->_saveThreshold > 0)) {
                    [self performSaveAndSuspendSaveTimer];
                }
            }
        }
    };

    // The design of the setter logic below is taken from the AWSDDAbstractLogger implementation.
    // For documentation please refer to the AWSDDAbstractLogger implementation.

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];
        NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");

        dispatch_async(globalLoggingQueue, ^{
            dispatch_async(self.loggerQueue, block);
        });
    }
}

- (NSTimeInterval)saveInterval {
    // The design of this method is taken from the AWSDDAbstractLogger implementation.
    // For extensive documentation please refer to the AWSDDAbstractLogger implementation.

    // Note: The internal implementation MUST access the colorsEnabled variable directly,
    // This method is designed explicitly for external access.
    //
    // Using "self." syntax to go through this method will cause immediate deadlock.
    // This is the intended result. Fix it by accessing the ivar directly.
    // Great strides have been take to ensure this is safe to do. Plus it's MUCH faster.

    NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");
    NSAssert(![self isOnInternalLoggerQueue], @"MUST access ivar directly, NOT via self.* syntax.");

    dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];

    __block NSTimeInterval result;

    dispatch_sync(globalLoggingQueue, ^{
        dispatch_sync(self.loggerQueue, ^{
            result = self->_saveInterval;
        });
    });

    return result;
}

- (void)setSaveInterval:(NSTimeInterval)interval {
    dispatch_block_t block = ^{
        @autoreleasepool {
            // C99 recommended floating point comparison macro
            // Read: isLessThanOrGreaterThan(floatA, floatB)

            if (/* saveInterval != interval */ islessgreater(self->_saveInterval, interval)) {
                self->_saveInterval = interval;

                // There are several cases we need to handle here.
                //
                // 1. If the saveInterval was previously enabled and it just got disabled,
                //    then we need to stop the saveTimer. (And we might as well release it.)
                //
                // 2. If the saveInterval was previously disabled and it just got enabled,
                //    then we need to setup the saveTimer. (Plus we might need to do an immediate save.)
                //
                // 3. If the saveInterval increased, then we need to reset the timer so that it fires at the later date.
                //
                // 4. If the saveInterval decreased, then we need to reset the timer so that it fires at an earlier date.
                //    (Plus we might need to do an immediate save.)

                if (self->_saveInterval > 0.0) {
                    if (self->_saveTimer == NULL) {
                        // Handles #2
                        //
                        // Since the saveTimer uses the unsavedTime to calculate it's first fireDate,
                        // if a save is needed the timer will fire immediately.

                        [self createSuspendedSaveTimer];
                        [self updateAndResumeSaveTimer];
                    } else {
                        // Handles #3
                        // Handles #4
                        //
                        // Since the saveTimer uses the unsavedTime to calculate it's first fireDate,
                        // if a save is needed the timer will fire immediately.

                        [self updateAndResumeSaveTimer];
                    }
                } else if (self->_saveTimer) {
                    // Handles #1

                    [self destroySaveTimer];
                }
            }
        }
    };

    // The design of the setter logic below is taken from the AWSDDAbstractLogger implementation.
    // For documentation please refer to the AWSDDAbstractLogger implementation.

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];
        NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");

        dispatch_async(globalLoggingQueue, ^{
            dispatch_async(self.loggerQueue, block);
        });
    }
}

- (NSTimeInterval)maxAge {
    // The design of this method is taken from the AWSDDAbstractLogger implementation.
    // For extensive documentation please refer to the AWSDDAbstractLogger implementation.

    // Note: The internal implementation MUST access the colorsEnabled variable directly,
    // This method is designed explicitly for external access.
    //
    // Using "self." syntax to go through this method will cause immediate deadlock.
    // This is the intended result. Fix it by accessing the ivar directly.
    // Great strides have been take to ensure this is safe to do. Plus it's MUCH faster.

    NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");
    NSAssert(![self isOnInternalLoggerQueue], @"MUST access ivar directly, NOT via self.* syntax.");

    dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];

    __block NSTimeInterval result;

    dispatch_sync(globalLoggingQueue, ^{
        dispatch_sync(self.loggerQueue, ^{
            result = self->_maxAge;
        });
    });

    return result;
}

- (void)setMaxAge:(NSTimeInterval)interval {
    dispatch_block_t block = ^{
        @autoreleasepool {
            // C99 recommended floating point comparison macro
            // Read: isLessThanOrGreaterThan(floatA, floatB)

            if (/* maxAge != interval */ islessgreater(self->_maxAge, interval)) {
                NSTimeInterval oldMaxAge = self->_maxAge;
                NSTimeInterval newMaxAge = interval;

                self->_maxAge = interval;

                // There are several cases we need to handle here.
                //
                // 1. If the maxAge was previously enabled and it just got disabled,
                //    then we need to stop the deleteTimer. (And we might as well release it.)
                //
                // 2. If the maxAge was previously disabled and it just got enabled,
                //    then we need to setup the deleteTimer. (Plus we might need to do an immediate delete.)
                //
                // 3. If the maxAge was increased,
                //    then we don't need to do anything.
                //
                // 4. If the maxAge was decreased,
                //    then we should do an immediate delete.

                BOOL shouldDeleteNow = NO;

                if (oldMaxAge > 0.0) {
                    if (newMaxAge <= 0.0) {
                        // Handles #1

                        [self destroyDeleteTimer];
                    } else if (oldMaxAge > newMaxAge) {
                        // Handles #4
                        shouldDeleteNow = YES;
                    }
                } else if (newMaxAge > 0.0) {
                    // Handles #2
                    shouldDeleteNow = YES;
                }

                if (shouldDeleteNow) {
                    [self performDelete];

                    if (self->_deleteTimer) {
                        [self updateDeleteTimer];
                    } else {
                        [self createAndStartDeleteTimer];
                    }
                }
            }
        }
    };

    // The design of the setter logic below is taken from the AWSDDAbstractLogger implementation.
    // For documentation please refer to the AWSDDAbstractLogger implementation.

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];
        NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");

        dispatch_async(globalLoggingQueue, ^{
            dispatch_async(self.loggerQueue, block);
        });
    }
}

- (NSTimeInterval)deleteInterval {
    // The design of this method is taken from the AWSDDAbstractLogger implementation.
    // For extensive documentation please refer to the AWSDDAbstractLogger implementation.

    // Note: The internal implementation MUST access the colorsEnabled variable directly,
    // This method is designed explicitly for external access.
    //
    // Using "self." syntax to go through this method will cause immediate deadlock.
    // This is the intended result. Fix it by accessing the ivar directly.
    // Great strides have been take to ensure this is safe to do. Plus it's MUCH faster.

    NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");
    NSAssert(![self isOnInternalLoggerQueue], @"MUST access ivar directly, NOT via self.* syntax.");

    dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];

    __block NSTimeInterval result;

    dispatch_sync(globalLoggingQueue, ^{
        dispatch_sync(self.loggerQueue, ^{
            result = self->_deleteInterval;
        });
    });

    return result;
}

- (void)setDeleteInterval:(NSTimeInterval)interval {
    dispatch_block_t block = ^{
        @autoreleasepool {
            // C99 recommended floating point comparison macro
            // Read: isLessThanOrGreaterThan(floatA, floatB)

            if (/* deleteInterval != interval */ islessgreater(self->_deleteInterval, interval)) {
                self->_deleteInterval = interval;

                // There are several cases we need to handle here.
                //
                // 1. If the deleteInterval was previously enabled and it just got disabled,
                //    then we need to stop the deleteTimer. (And we might as well release it.)
                //
                // 2. If the deleteInterval was previously disabled and it just got enabled,
                //    then we need to setup the deleteTimer. (Plus we might need to do an immediate delete.)
                //
                // 3. If the deleteInterval increased, then we need to reset the timer so that it fires at the later date.
                //
                // 4. If the deleteInterval decreased, then we need to reset the timer so that it fires at an earlier date.
                //    (Plus we might need to do an immediate delete.)

                if (self->_deleteInterval > 0.0) {
                    if (self->_deleteTimer == NULL) {
                        // Handles #2
                        //
                        // Since the deleteTimer uses the lastDeleteTime to calculate it's first fireDate,
                        // if a delete is needed the timer will fire immediately.

                        [self createAndStartDeleteTimer];
                    } else {
                        // Handles #3
                        // Handles #4
                        //
                        // Since the deleteTimer uses the lastDeleteTime to calculate it's first fireDate,
                        // if a save is needed the timer will fire immediately.

                        [self updateDeleteTimer];
                    }
                } else if (self->_deleteTimer) {
                    // Handles #1

                    [self destroyDeleteTimer];
                }
            }
        }
    };

    // The design of the setter logic below is taken from the AWSDDAbstractLogger implementation.
    // For documentation please refer to the AWSDDAbstractLogger implementation.

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];
        NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");

        dispatch_async(globalLoggingQueue, ^{
            dispatch_async(self.loggerQueue, block);
        });
    }
}

- (BOOL)deleteOnEverySave {
    // The design of this method is taken from the AWSDDAbstractLogger implementation.
    // For extensive documentation please refer to the AWSDDAbstractLogger implementation.

    // Note: The internal implementation MUST access the colorsEnabled variable directly,
    // This method is designed explicitly for external access.
    //
    // Using "self." syntax to go through this method will cause immediate deadlock.
    // This is the intended result. Fix it by accessing the ivar directly.
    // Great strides have been take to ensure this is safe to do. Plus it's MUCH faster.

    NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");
    NSAssert(![self isOnInternalLoggerQueue], @"MUST access ivar directly, NOT via self.* syntax.");

    dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];

    __block BOOL result;

    dispatch_sync(globalLoggingQueue, ^{
        dispatch_sync(self.loggerQueue, ^{
            result = self->_deleteOnEverySave;
        });
    });

    return result;
}

- (void)setDeleteOnEverySave:(BOOL)flag {
    dispatch_block_t block = ^{
        self->_deleteOnEverySave = flag;
    };

    // The design of the setter logic below is taken from the AWSDDAbstractLogger implementation.
    // For documentation please refer to the AWSDDAbstractLogger implementation.

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_queue_t globalLoggingQueue = [AWSDDLog loggingQueue];
        NSAssert(![self isOnGlobalLoggingQueue], @"Core architecture requirement failure");

        dispatch_async(globalLoggingQueue, ^{
            dispatch_async(self.loggerQueue, block);
        });
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark Public API
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (void)savePendingLogEntries {
    dispatch_block_t block = ^{
        @autoreleasepool {
            [self performSaveAndSuspendSaveTimer];
        }
    };

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_async(self.loggerQueue, block);
    }
}

- (void)deleteOldLogEntries {
    dispatch_block_t block = ^{
        @autoreleasepool {
            [self performDelete];
        }
    };

    if ([self isOnInternalLoggerQueue]) {
        block();
    } else {
        dispatch_async(self.loggerQueue, block);
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma mark AWSDDLogger
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

- (void)didAddLogger {
    // If you override me be sure to invoke [super didAddLogger];

    [self createSuspendedSaveTimer];

    [self createAndStartDeleteTimer];
}

- (void)willRemoveLogger {
    // If you override me be sure to invoke [super willRemoveLogger];

    [self performSaveAndSuspendSaveTimer];

    [self destroySaveTimer];
    [self destroyDeleteTimer];
}

- (void)logMessage:(AWSDDLogMessage *)logMessage {
    if ([self db_log:logMessage]) {
        BOOL firstUnsavedEntry = (++_unsavedCount == 1);

        if ((_unsavedCount >= _saveThreshold) && (_saveThreshold > 0)) {
            [self performSaveAndSuspendSaveTimer];
        } else if (firstUnsavedEntry) {
            _unsavedTime = dispatch_time(DISPATCH_TIME_NOW, 0);
            [self updateAndResumeSaveTimer];
        }
    }
}

- (void)flush {
    // This method is invoked by AWSDDLog's flushLog method.
    //
    // It is called automatically when the application quits,
    // or if the developer invokes AWSDDLog's flushLog method prior to crashing or something.

    [self performSaveAndSuspendSaveTimer];
}

@end