#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <errno.h>

#include <pthread.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>

#include <fcntl.h>


#include "private.h"
#include "default.h"
#include "sysinfo.h"

fastwriter_t *fastwriter_init(const char *fs, fastwriter_flags_t flags) {
    fastwriter_t *ctx;
    
    ctx = (fastwriter_t*)malloc(sizeof(fastwriter_t));
    if (!ctx) return ctx;
    
    memset(ctx, 0, sizeof(fastwriter_t));
    ctx->params.flags = flags;
    ctx->api = &fastwriter_default_api;
    
    return ctx;
}

void fastwriter_destroy(fastwriter_t *ctx) {
    free(ctx);
}

int fastwriter_set_buffer_size(fastwriter_t *ctx, size_t buffer_size) {
    ctx->params.buffer_size = buffer_size;
    
    return 0;
}

static void *fastwriter_writer_thread(void *user);

int fastwriter_open(fastwriter_t *ctx, const char *name, fastwriter_flags_t flags) {
    int i;
    int err;
    int e[4];
    
    ctx->flags = flags | ctx->params.flags;
    
    switch (ctx->params.buffer_size) {
     case FASTWRITER_BUFFER_DEFAULT:
        ctx->size = FASTWRITER_DEFAULT_BUFFER_SIZE;
	break;
     case FASTWRITER_BUFFER_MAX:
        ctx->size = get_free_memory();

	if ((ctx->size - FASTWRITER_RESERVE_MEMORY) < FASTWRITER_DEFAULT_BUFFER_SIZE)
    	    ctx->size = FASTWRITER_DEFAULT_BUFFER_SIZE;
	else
	    ctx->size -= FASTWRITER_RESERVE_MEMORY;

        break;
     default:
	ctx->size = ctx->params.buffer_size;
    }
    
    ctx->buffer = malloc(ctx->size);
    if (!ctx->buffer) {
	fastwriter_close(ctx);
	return ENOMEM;
    }
    ctx->err = 0;
    ctx->written = 0;
    ctx->commited = 0;
    ctx->chunked = 0;
    
    ctx->tail = 0;
    ctx->head = 0;
    ctx->pos = 0;
    
    err = ctx->api->open(ctx, name, ctx->flags);
    if (err) {
	fastwriter_close(ctx);
	return err;
    }

    e[0] = pthread_mutex_init(&ctx->data_cond_mutex, NULL);
    e[1] = pthread_mutex_init(&ctx->space_cond_mutex, NULL);
    e[2] = pthread_cond_init(&ctx->data_cond, NULL);
    e[3] = pthread_cond_init(&ctx->space_cond, NULL);
    
    if (e[0]|e[1]|e[2]|e[3]) {
	if (!e[3]) pthread_cond_destroy(&ctx->space_cond);
	if (!e[2]) pthread_cond_destroy(&ctx->data_cond);
	if (!e[1]) pthread_mutex_destroy(&ctx->space_cond_mutex);
	if (!e[0]) pthread_mutex_destroy(&ctx->data_cond_mutex);
	
	fastwriter_close(ctx);
	
	for (i = 0; i < 4; i++) 
	    if (e[i]) return e[i];
    }
    
    ctx->clean_locks = 1;
    ctx->run_flag = 1;
    
    err = pthread_create(&ctx->wthread, NULL, &fastwriter_writer_thread, ctx);
    if (err) {
	ctx->run_flag = 0;
	fastwriter_close(ctx);
	return err;
    }
    
    return 0;
}

int fastwriter_close(fastwriter_t *ctx) {
    if ((!ctx->err)&&(ctx->pos != ctx->head))
	return EBADFD;

    if (ctx->run_flag) {
	ctx->run_flag = 0;

	pthread_mutex_lock(&ctx->data_cond_mutex);
	pthread_cond_broadcast(&ctx->data_cond);
	pthread_mutex_unlock(&ctx->data_cond_mutex);
	
	pthread_join(ctx->wthread, NULL);
    }
    
    if (ctx->clean_locks) {
	pthread_cond_destroy(&ctx->space_cond);
	pthread_cond_destroy(&ctx->data_cond);
	pthread_mutex_destroy(&ctx->space_cond_mutex);
	pthread_mutex_destroy(&ctx->data_cond_mutex);
    
	ctx->clean_locks = 0;
    }
    
    ctx->api->close(ctx);

    if (ctx->buffer) {
	free(ctx->buffer);
	ctx->buffer = NULL;
    }
    
    return 0;
    
}


static inline size_t fastwriter_compute_free_space(fastwriter_t *ctx) {
    if (ctx->pos < ctx->tail) return ctx->tail - ctx->pos;
    return ctx->tail + ctx->size - ctx->pos - 1;
}

int fastwriter_get_stats(fastwriter_t *ctx, fastwriter_stats_t *stats) {
    stats->buffer_size = ctx->size;
    stats->buffer_used = ctx->size - fastwriter_compute_free_space(ctx);
    stats->buffer_max = ctx->max_usage;
    stats->commited = ctx->commited;
    stats->written = ctx->written;
    return 0;
}


static void *fastwriter_writer_thread(void *user) {
    int err = 0;
    fastwriter_write_flags_t flags;
    size_t size;
    size_t head;

    fastwriter_t *ctx = (fastwriter_t*)user;

    while ((ctx->run_flag)||(ctx->head != ctx->tail)) {
	if (ctx->head != ctx->tail) {
	    head = ctx->head;

	    if (head > ctx->tail) {
		size = head - ctx->tail;
		flags = FASTWRITER_WRITE_FLAGS_DEFAULT;
	    } else { 
		size = ctx->size - ctx->tail;
		flags = FASTWRITER_WRITE_FLAG_FORCE;
	    }
	    
	    if (!ctx->run_flag) 
		flags |= FASTWRITER_WRITE_FLAG_FORCE;

	    err = ctx->api->write(ctx, flags, size, ctx->buffer + ctx->tail, &size);
	    if (err) {
		ctx->err = err;
		ctx->run_flag = 0;

		pthread_mutex_lock(&ctx->space_cond_mutex);
		pthread_cond_broadcast(&ctx->space_cond);
		pthread_mutex_unlock(&ctx->space_cond_mutex);
		
		return NULL;
	    }
	    
	    if (size > 0) {
		ctx->written += size;
		
		size += ctx->tail;
		if (size == ctx->size) ctx->tail = 0;
		else ctx->tail = size;
	    
		pthread_mutex_lock(&ctx->space_cond_mutex);
		pthread_cond_broadcast(&ctx->space_cond);
		pthread_mutex_unlock(&ctx->space_cond_mutex);
	    } else {
		pthread_mutex_lock(&ctx->data_cond_mutex);
		while ((ctx->run_flag)&&(ctx->head == head)) {
		    pthread_cond_wait(&ctx->data_cond, &ctx->data_cond_mutex);
		}
	    }
	} else {
	    pthread_mutex_lock(&ctx->data_cond_mutex);
	    while ((ctx->run_flag)&&(ctx->head == ctx->tail)) {
		pthread_cond_wait(&ctx->data_cond, &ctx->data_cond_mutex);
	    }
	}
    }
    
    return NULL;
}


int fastwriter_push(fastwriter_t *ctx, size_t size, const void *data) {
    size_t part1, end;
    size_t free = fastwriter_compute_free_space(ctx);

    if (free < size) {
	ctx->max_usage = ctx->size;
	
	if ((ctx->flags&FASTWRITER_FLAGS_BLOCK)==0)
	    return EWOULDBLOCK;
	
	pthread_mutex_lock(&ctx->space_cond_mutex);
	while ((ctx->run_flag)&&(fastwriter_compute_free_space(ctx) < size)) {
	    pthread_cond_wait(&ctx->space_cond, &ctx->space_cond_mutex);
	}
	pthread_mutex_unlock(&ctx->space_cond_mutex);
    } else {
	end = ctx->size - (free - size);
	if (end > ctx->max_usage) ctx->max_usage = end;
    }
    
    if (!ctx->run_flag) {
	if (ctx->err) return ctx->err;
	return EBADFD;
    }
    
    if (ctx->pos < ctx->tail) end = ctx->tail;
    else end = ctx->size;
    

    part1 = end - ctx->pos;
    
    if (part1 > size) {
	    // tail < pos (we have checked for free space)
	end = size - part1;
	memcpy(ctx->buffer + ctx->pos, data, part1);
	memcpy(ctx->buffer, data + part1, end);
	ctx->pos = end;
    } else {
	memcpy(ctx->buffer + ctx->pos, data, size);
	ctx->pos += size;
	
	if (ctx->pos == ctx->size) ctx->pos = 0;
    }
    
    ctx->chunked += size;
    
    return 0;
}


int fastwriter_commit(fastwriter_t *ctx) {
    ctx->head = ctx->pos;

    pthread_mutex_lock(&ctx->data_cond_mutex);
    pthread_cond_broadcast(&ctx->data_cond);
    pthread_mutex_unlock(&ctx->data_cond_mutex);
    
    ctx->commited += ctx->chunked;
    ctx->chunked = 0;

    return 0;
}


int fastwriter_cancel(fastwriter_t *ctx) {
    ctx->pos = ctx->head;
    
    ctx->chunked = 0;
    
    return 0;
}


int fastwriter_push_data(fastwriter_t *ctx, size_t size, const void *buf) {
    int err;
    err = fastwriter_push(ctx, size, buf);
    if (err) return err;
    
    err = fastwriter_commit(ctx);
    if (err) fastwriter_cancel(ctx);

    return err;
}