#include "../../include/replay_buffer/replay_buffer_disk.h"
#include "../../include/utils.h"

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#include <assert.h>

#define REPLAY_BUFFER_FILE_SIZE_BYTES 1024 * 1024 * 256 /* 256MB */
#define FILE_PREFIX "Replay"

static void gsr_replay_buffer_disk_set_impl_funcs(gsr_replay_buffer_disk *self);

static void gsr_av_packet_disk_init(gsr_av_packet_disk *self, const AVPacket *av_packet, size_t data_index, double timestamp) {
    self->packet = *av_packet;
    self->packet.data = NULL;
    self->data_index = data_index;
    self->timestamp = timestamp;
}

static gsr_replay_buffer_file* gsr_replay_buffer_file_create(char *replay_directory, size_t replay_storage_counter, double timestamp, int *replay_storage_fd) {
    gsr_replay_buffer_file *self = calloc(1, sizeof(gsr_replay_buffer_file));
    if(!self) {
        fprintf(stderr, "gsr error: gsr_av_packet_file_init: failed to create buffer file\n");
        return NULL;
    }

    if(create_directory_recursive(replay_directory) != 0) {
        fprintf(stderr, "gsr error: gsr_av_packet_file_init: failed to create replay directory: %s\n", replay_directory);
        free(self);
        return NULL;
    }

    char filename[PATH_MAX];
    snprintf(filename, sizeof(filename), "%s/%s_%d.gsr", replay_directory, FILE_PREFIX, (int)replay_storage_counter);
    *replay_storage_fd = creat(filename, 0700);
    if(*replay_storage_fd <= 0) {
        fprintf(stderr, "gsr error: gsr_av_packet_file_init: failed to create replay file: %s\n", filename);
        free(self);
        return NULL;
    }

    self->id = replay_storage_counter;
    self->start_timestamp = timestamp;
    self->end_timestamp = timestamp;
    self->ref_counter = 1;
    self->fd = -1;

    self->packets = NULL;
    self->capacity_num_packets = 0;
    self->num_packets = 0;
    return self;
}

static gsr_replay_buffer_file* gsr_replay_buffer_file_ref(gsr_replay_buffer_file *self) {
    if(self->ref_counter >= 1)
        ++self->ref_counter;
    return self;
}

static void gsr_replay_buffer_file_free(gsr_replay_buffer_file *self, const char *replay_directory) {
    self->ref_counter = 0;

    if(self->fd > 0) {
        close(self->fd);
        self->fd = -1;
    }

    char filename[PATH_MAX];
    snprintf(filename, sizeof(filename), "%s/%s_%d.gsr", replay_directory, FILE_PREFIX, (int)self->id);
    remove(filename);

    if(self->packets) {
        free(self->packets);
        self->packets = NULL;
    }
    self->num_packets = 0;
    self->capacity_num_packets = 0;

    free(self);
}

static void gsr_replay_buffer_file_unref(gsr_replay_buffer_file *self, const char *replay_directory) {
    if(self->ref_counter > 0)
        --self->ref_counter;

    if(self->ref_counter <= 0)
        gsr_replay_buffer_file_free(self, replay_directory);
}

static void gsr_replay_buffer_disk_clear(gsr_replay_buffer *replay_buffer) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;

    for(size_t i = 0; i < self->num_files; ++i) {
        gsr_replay_buffer_file_unref(self->files[i], self->replay_directory);
    }
    self->num_files = 0;

    if(self->storage_fd > 0) {
        close(self->storage_fd);
        self->storage_fd = 0;
    }

    self->storage_num_bytes_written = 0;
}

static void gsr_replay_buffer_disk_destroy(gsr_replay_buffer *replay_buffer) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    gsr_replay_buffer_disk_clear(replay_buffer);

    if(self->owns_directory) {
        remove(self->replay_directory);
        self->owns_directory = false;
    }
}

static bool file_write_all(int fd, const uint8_t *data, size_t size, size_t *bytes_written_total) {
    *bytes_written_total = 0;
    while(*bytes_written_total < size) {
        const ssize_t bytes_written = write(fd, data + *bytes_written_total, size - *bytes_written_total);
        if(bytes_written == -1) {
            if(errno == EAGAIN)
                continue;
            else
                return false;
        }
        *bytes_written_total += bytes_written;
    }
    return true;
}

static bool gsr_replay_buffer_disk_create_next_file(gsr_replay_buffer_disk *self, double timestamp) {
    if(self->num_files + 1 >= GSR_REPLAY_BUFFER_CAPACITY_NUM_FILES) {
        fprintf(stderr, "gsr error: gsr_replay_buffer_disk_create_next_file: too many replay buffer files created! (> %d), either reduce the replay buffer time or report this as a bug\n", (int)GSR_REPLAY_BUFFER_CAPACITY_NUM_FILES);
        return false;
    }

    gsr_replay_buffer_file *replay_buffer_file = gsr_replay_buffer_file_create(self->replay_directory, self->storage_counter, timestamp, &self->storage_fd);
    if(!replay_buffer_file)
        return false;

    self->files[self->num_files] = replay_buffer_file;
    ++self->num_files;
    ++self->storage_counter;
    return true;
}

static bool gsr_replay_buffer_disk_append_to_current_file(gsr_replay_buffer_disk *self, const AVPacket *av_packet, double timestamp) {
    gsr_replay_buffer_file *replay_buffer_file = self->files[self->num_files - 1];
    replay_buffer_file->end_timestamp = timestamp;

    if(replay_buffer_file->num_packets + 1 >= replay_buffer_file->capacity_num_packets) {
        size_t new_capacity_num_packets = replay_buffer_file->capacity_num_packets * 2;
        if(new_capacity_num_packets == 0)
            new_capacity_num_packets = 256;

        void *new_packets = realloc(replay_buffer_file->packets, new_capacity_num_packets * sizeof(gsr_av_packet_disk));
        if(!new_packets) {
            fprintf(stderr, "gsr error: gsr_replay_buffer_disk_append_to_current_file: failed to reallocate replay buffer file packets\n");
            return false;
        }

        replay_buffer_file->capacity_num_packets = new_capacity_num_packets;
        replay_buffer_file->packets = new_packets;
    }

    gsr_av_packet_disk *packet = &replay_buffer_file->packets[replay_buffer_file->num_packets];
    gsr_av_packet_disk_init(packet, av_packet, self->storage_num_bytes_written, timestamp);
    ++replay_buffer_file->num_packets;

    size_t bytes_written = 0;
    const bool file_written = file_write_all(self->storage_fd, av_packet->data, av_packet->size, &bytes_written);
    self->storage_num_bytes_written += bytes_written;
    if(self->storage_num_bytes_written >= REPLAY_BUFFER_FILE_SIZE_BYTES) {
        self->storage_num_bytes_written = 0;
        close(self->storage_fd);
        self->storage_fd = 0;
    }

    return file_written;
}

static void gsr_replay_buffer_disk_remove_first_file(gsr_replay_buffer_disk *self) {
    gsr_replay_buffer_file_unref(self->files[0], self->replay_directory);
    for(size_t i = 1; i < self->num_files; ++i) {
        self->files[i - 1] = self->files[i];
    }
    --self->num_files;
}

static bool gsr_replay_buffer_disk_append(gsr_replay_buffer *replay_buffer, const AVPacket *av_packet, double timestamp) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    bool success = false;

    if(self->storage_fd <= 0) {
        if(!gsr_replay_buffer_disk_create_next_file(self, timestamp))
            goto done;
    }

    const bool data_written = gsr_replay_buffer_disk_append_to_current_file(self, av_packet, timestamp);

    if(self->num_files > 1) {
        const double buffer_time_accumulated = timestamp - self->files[1]->start_timestamp;
        if(buffer_time_accumulated >= self->replay_buffer_time)
            gsr_replay_buffer_disk_remove_first_file(self);
    }

    success = data_written;

    done:
    return success;
}

static AVPacket* gsr_replay_buffer_disk_iterator_get_packet(gsr_replay_buffer *replay_buffer, gsr_replay_buffer_iterator iterator) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    assert(iterator.file_index < self->num_files);
    assert(iterator.packet_index < self->files[iterator.file_index]->num_packets);
    return &self->files[iterator.file_index]->packets[iterator.packet_index].packet;
}

static uint8_t* gsr_replay_buffer_disk_iterator_get_packet_data(gsr_replay_buffer *replay_buffer, gsr_replay_buffer_iterator iterator) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    assert(iterator.file_index < self->num_files);
    gsr_replay_buffer_file *file = self->files[iterator.file_index];
    assert(iterator.packet_index < file->num_packets);

    if(file->fd <= 0) {
        char filename[PATH_MAX];
        snprintf(filename, sizeof(filename), "%s/%s_%d.gsr", self->replay_directory, FILE_PREFIX, (int)file->id);
        file->fd = open(filename, O_RDONLY);
        if(file->fd <= 0) {
            fprintf(stderr, "gsr error: gsr_replay_buffer_disk_iterator_get_packet_data: failed to open file\n");
            return NULL;
        }
    }

    const gsr_av_packet_disk *packet = &self->files[iterator.file_index]->packets[iterator.packet_index];
    if(lseek(file->fd, packet->data_index, SEEK_SET) == -1) {
        fprintf(stderr, "gsr error: gsr_replay_buffer_disk_iterator_get_packet_data: failed to seek\n");
        return NULL;
    }

    uint8_t *packet_data = malloc(packet->packet.size);
    if(read(file->fd, packet_data, packet->packet.size) != packet->packet.size) {
        fprintf(stderr, "gsr error: gsr_replay_buffer_disk_iterator_get_packet_data: failed to read data from file\n");
        free(packet_data);
        return NULL;
    }

    return packet_data;
}

static gsr_replay_buffer* gsr_replay_buffer_disk_clone(gsr_replay_buffer *replay_buffer) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    gsr_replay_buffer_disk *destination = calloc(1, sizeof(gsr_replay_buffer_disk));
    if(!destination)
        return NULL;

    gsr_replay_buffer_disk_set_impl_funcs(destination);

    destination->replay_buffer_time = self->replay_buffer_time;
    destination->storage_counter = self->storage_counter;
    destination->storage_num_bytes_written = self->storage_num_bytes_written;
    destination->storage_fd = 0; // We only want to read from the clone. If there is a need to write to it in the future then TODO change this

    for(size_t i = 0; i < self->num_files; ++i) {
        destination->files[i] = gsr_replay_buffer_file_ref(self->files[i]);
    }
    destination->num_files = self->num_files;

    snprintf(destination->replay_directory, sizeof(destination->replay_directory), "%s", self->replay_directory);
    destination->owns_directory = false;

    return (gsr_replay_buffer*)destination;
}

/* Binary search */
static size_t gsr_replay_buffer_file_find_packet_index_by_time_passed(const gsr_replay_buffer_file *self, int seconds) {
    const double now = clock_get_monotonic_seconds();
    if(self->num_packets == 0) {
        return 0;
    }

    size_t lower_bound = 0;
    size_t upper_bound = self->num_packets;
    size_t index = 0;

    for(;;) {
        index = lower_bound + (upper_bound - lower_bound) / 2;
        const gsr_av_packet_disk *packet = &self->packets[index];
        const double time_passed_since_packet = now - packet->timestamp;
        if(time_passed_since_packet >= seconds) {
            if(lower_bound == index)
                break;
            lower_bound = index;
        } else {
            if(upper_bound == index)
                break;
            upper_bound = index;
        }
    }

    return index;
}

/* Binary search */
static gsr_replay_buffer_iterator gsr_replay_buffer_disk_find_file_index_by_time_passed(gsr_replay_buffer *replay_buffer, int seconds) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;

    const double now = clock_get_monotonic_seconds();
    if(self->num_files == 0) {
        return (gsr_replay_buffer_iterator){0, 0};
    }

    size_t lower_bound = 0;
    size_t upper_bound = self->num_files;
    size_t file_index = 0;

    for(;;) {
        file_index = lower_bound + (upper_bound - lower_bound) / 2;
        const gsr_replay_buffer_file *file = self->files[file_index];
        const double time_passed_since_file_start = now - file->start_timestamp;
        const double time_passed_since_file_end = now - file->end_timestamp;
        if(time_passed_since_file_start >= seconds && time_passed_since_file_end <= seconds) {
            break;
        } else if(time_passed_since_file_start >= seconds) {
            if(lower_bound == file_index)
                break;
            lower_bound = file_index;
        } else {
            if(upper_bound == file_index)
                break;
            upper_bound = file_index;
        }
    }

    const gsr_replay_buffer_file *file = self->files[file_index];
    const size_t packet_index = gsr_replay_buffer_file_find_packet_index_by_time_passed(file, seconds);

    return (gsr_replay_buffer_iterator){packet_index, file_index};
}

static gsr_replay_buffer_iterator gsr_replay_buffer_disk_find_keyframe(gsr_replay_buffer *replay_buffer, gsr_replay_buffer_iterator start_iterator, int stream_index, bool invert_stream_index) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    gsr_replay_buffer_iterator keyframe_iterator = {(size_t)-1, 0};
    size_t packet_index = start_iterator.packet_index;
    for(size_t file_index = start_iterator.file_index; file_index < self->num_files; ++file_index) {
        const gsr_replay_buffer_file *file = self->files[file_index];
        for(; packet_index < file->num_packets; ++packet_index) {
            const gsr_av_packet_disk *packet = &file->packets[packet_index];
            if((packet->packet.flags & AV_PKT_FLAG_KEY) && (invert_stream_index ? packet->packet.stream_index != stream_index : packet->packet.stream_index == stream_index)) {
                keyframe_iterator.packet_index = packet_index;
                keyframe_iterator.file_index = file_index;
                goto done;
            }
        }
        packet_index = 0;
    }
    done:
    return keyframe_iterator;
}

static bool gsr_replay_buffer_disk_iterator_next(gsr_replay_buffer *replay_buffer, gsr_replay_buffer_iterator *iterator) {
    gsr_replay_buffer_disk *self = (gsr_replay_buffer_disk*)replay_buffer;
    if(iterator->file_index >= self->num_files)
        return false;

    if(iterator->packet_index + 1 >= self->files[iterator->file_index]->num_packets) {
        if(iterator->file_index + 1 >= self->num_files)
            return false;

        if(self->files[iterator->file_index + 1]->num_packets == 0)
            return false;

        ++iterator->file_index;
        iterator->packet_index = 0;
        return true;
    } else {
        ++iterator->packet_index;
        return true;
    }
}

static void get_current_time(char *time_str, size_t time_str_size) {
    time_t now = time(NULL);
    struct tm *t = localtime(&now);
    strftime(time_str, time_str_size - 1, "%Y-%m-%d_%H-%M-%S", t);
}

static void gsr_replay_buffer_disk_set_impl_funcs(gsr_replay_buffer_disk *self) {
    self->replay_buffer.destroy = gsr_replay_buffer_disk_destroy;
    self->replay_buffer.append = gsr_replay_buffer_disk_append;
    self->replay_buffer.clear = gsr_replay_buffer_disk_clear;
    self->replay_buffer.iterator_get_packet = gsr_replay_buffer_disk_iterator_get_packet;
    self->replay_buffer.iterator_get_packet_data = gsr_replay_buffer_disk_iterator_get_packet_data;
    self->replay_buffer.clone = gsr_replay_buffer_disk_clone;
    self->replay_buffer.find_packet_index_by_time_passed = gsr_replay_buffer_disk_find_file_index_by_time_passed;
    self->replay_buffer.find_keyframe = gsr_replay_buffer_disk_find_keyframe;
    self->replay_buffer.iterator_next = gsr_replay_buffer_disk_iterator_next;
}

gsr_replay_buffer* gsr_replay_buffer_disk_create(const char *replay_directory, double replay_buffer_time) {
    assert(replay_buffer_time > 0);
    gsr_replay_buffer_disk *replay_buffer = calloc(1, sizeof(gsr_replay_buffer_disk));
    if(!replay_buffer)
        return NULL;

    char time_str[128];
    get_current_time(time_str, sizeof(time_str));

    replay_buffer->num_files = 0;
    replay_buffer->storage_counter = 0;
    replay_buffer->replay_buffer_time = replay_buffer_time;
    snprintf(replay_buffer->replay_directory, sizeof(replay_buffer->replay_directory), "%s/gsr-replay-%s.gsr", replay_directory, time_str);
    replay_buffer->owns_directory = true;

    gsr_replay_buffer_disk_set_impl_funcs(replay_buffer);
    return (gsr_replay_buffer*)replay_buffer;
}
