/*
 * Thin C wrapper around mspack's LZX decompressor for use from Rust FFI.
 * This provides a simple buffer-to-buffer decompression function.
 */
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>

/* Stub for xenia_log (referenced by lzxd.c debug macros) */
void xenia_log(const char *fmt, ...) {
    (void)fmt;
}

/* Pull in mspack headers from xenia's third_party */
#define HAVE_CONFIG_H
#include "config.h"
#include "mspack.h"
#include "system.h"
#include "lzx.h"

/* Memory-backed file for mspack I/O */
typedef struct {
    struct mspack_system sys;
    void *buffer;
    off_t buffer_size;
    off_t offset;
} mspack_memory_file;

static struct mspack_file *mem_open(struct mspack_system *self, const char *fn, int mode) {
    (void)self; (void)fn; (void)mode;
    return NULL;
}
static void mem_close(struct mspack_file *file) { (void)file; }

static int mem_read(struct mspack_file *file, void *buffer, int chars) {
    mspack_memory_file *memfile = (mspack_memory_file *)file;
    off_t remaining = memfile->buffer_size - memfile->offset;
    off_t total = (off_t)chars < remaining ? (off_t)chars : remaining;
    memcpy(buffer, (uint8_t *)memfile->buffer + memfile->offset, total);
    memfile->offset += total;
    return (int)total;
}

static int mem_write(struct mspack_file *file, void *buffer, int chars) {
    mspack_memory_file *memfile = (mspack_memory_file *)file;
    off_t remaining = memfile->buffer_size - memfile->offset;
    off_t total = (off_t)chars < remaining ? (off_t)chars : remaining;
    memcpy((uint8_t *)memfile->buffer + memfile->offset, buffer, total);
    memfile->offset += total;
    return (int)total;
}

static int mem_seek(struct mspack_file *file, off_t offset, int mode) {
    (void)file; (void)offset; (void)mode;
    return -1;
}

static off_t mem_tell(struct mspack_file *file) {
    (void)file;
    return 0;
}

static void mem_msg(struct mspack_file *file, const char *format, ...) {
    (void)file; (void)format;
}

static void *mem_alloc(struct mspack_system *self, size_t bytes) {
    (void)self;
    return calloc(bytes, 1);
}

static void mem_free(void *ptr) { free(ptr); }

static void mem_copy(void *src, void *dest, size_t bytes) {
    memcpy(dest, src, bytes);
}

/*
 * Decompress LZX data from a memory buffer.
 * Returns 0 on success, non-zero on error.
 */
int xenia_lzx_decompress(
    const void *lzx_data, uint32_t lzx_len,
    void *dest, uint32_t dest_len,
    uint32_t window_size)
{
    /* Calculate window_bits from window_size (find the bit position) */
    uint32_t window_bits = 0;
    uint32_t tmp = window_size;
    while (tmp > 1) {
        tmp >>= 1;
        window_bits++;
    }
    if ((1u << window_bits) != window_size || window_bits < 15 || window_bits > 21) {
        return 1;
    }

    /* Set up mspack memory system */
    struct mspack_system sys;
    memset(&sys, 0, sizeof(sys));
    sys.open = mem_open;
    sys.close = mem_close;
    sys.read = mem_read;
    sys.write = mem_write;
    sys.seek = mem_seek;
    sys.tell = mem_tell;
    sys.message = mem_msg;
    sys.alloc = mem_alloc;
    sys.free = mem_free;
    sys.copy = mem_copy;

    mspack_memory_file src_file;
    memset(&src_file, 0, sizeof(src_file));
    src_file.buffer = (void *)lzx_data;
    src_file.buffer_size = (off_t)lzx_len;
    src_file.offset = 0;

    mspack_memory_file dst_file;
    memset(&dst_file, 0, sizeof(dst_file));
    dst_file.buffer = dest;
    dst_file.buffer_size = (off_t)dest_len;
    dst_file.offset = 0;

    struct lzxd_stream *lzxd = lzxd_init(
        &sys,
        (struct mspack_file *)&src_file,
        (struct mspack_file *)&dst_file,
        (int)window_bits,
        0,       /* reset_interval: 0 = never reset */
        0x8000,  /* input_buffer_size */
        (off_t)dest_len,
        0        /* is_delta */
    );

    if (!lzxd) {
        return 2;
    }

    int result = lzxd_decompress(lzxd, (off_t)dest_len);
    lzxd_free(lzxd);
    return result;
}