#include <stdio.h>
#include <string.h>
#include <libgen.h>
#include <expat.h>
#include <SDL.h>
#include "logging.h"
#include "base64.h"
#include "compression.h"
#include "map.h"
#include "resources/image.h"

struct tmx {
	char *dirname;
	struct map *map;
	enum {
		TMX_PARSING_NONE = 0,
		TMX_PARSING_MAP,
		TMX_PARSING_TILESET,
		TMX_PARSING_IMAGE,
		TMX_PARSING_LAYER,
		TMX_PARSING_DATA
	} parsing;
	struct tileset *cur_tileset;
	struct layer *cur_layer;
	enum {
		TMX_DATA_ENC_NONE = 0,
		TMX_DATA_ENC_BASE64,
		TMX_DATA_ENC_CSV
	} data_encoding;
	enum {
		TMX_DATA_COMP_NONE = 0,
		TMX_DATA_COMP_GZIP,
		TMX_DATA_COMP_ZLIB
	} data_compression;
	char *layer_data;
};

#define foreach_tmx_attr(attr)                                                \
	for (; (attr)[0] != NULL; (attr) += 2)

#define tmx_get_int_attr(attr, name, p)                                       \
	do {                                                                  \
		if (strcmp((attr)[0], (name)) == 0) {                         \
			if (sscanf((attr)[1], "%d", (p)) != 1) {              \
				err(1, "Invalid \"%s\" attribute", (name));   \
			}                                                     \
		}                                                             \
	} while (0);

#define tmx_get_string_attr(attr, name, p)                                    \
	do {                                                                  \
		if (strcmp((attr)[0], (name)) == 0) {                         \
			(p) = strdup((attr)[1]);                              \
		}                                                             \
	} while (0);

static void
tmx_start_map(struct tmx *cur_tmx, const char **attr)
{
	if (cur_tmx->map != NULL) {
		err(1, "Found multiple maps in TMX file");
	}

	cur_tmx->map = malloc(sizeof(*cur_tmx->map));
	if (cur_tmx->map == NULL) {
		err(1, "Failed to allocate map");
	}
	memset(cur_tmx->map, 0, sizeof(*cur_tmx->map));

	foreach_tmx_attr (attr) {
		tmx_get_int_attr(attr, "width", &cur_tmx->map->width);
		tmx_get_int_attr(attr, "height", &cur_tmx->map->height);
		tmx_get_int_attr(attr, "tilewidth", &cur_tmx->map->tilewidth);
		tmx_get_int_attr(attr, "tileheight", &cur_tmx->map->tileheight);
	}
}

static void
tmx_start_tileset(struct tmx *cur_tmx, const char **attr)
{
	struct tileset *new_tileset;

	if (cur_tmx->map == NULL) {
		err(1, "Malformed TMX file");
	}

	new_tileset = malloc(sizeof(*new_tileset));
	if (new_tileset == NULL) {
		err(1, "Failed to allocate tileset");
	}
	memset(new_tileset, 0, sizeof(*new_tileset));

	if (cur_tmx->cur_tileset == NULL) {
		cur_tmx->map->tilesets = new_tileset;
	} else {
		cur_tmx->cur_tileset->next = new_tileset;
	}
	cur_tmx->cur_tileset = new_tileset;

	foreach_tmx_attr (attr) {
		tmx_get_int_attr(attr, "firstgid",
				&cur_tmx->cur_tileset->firstgid);
		tmx_get_int_attr(attr, "tilewidth",
				&cur_tmx->cur_tileset->tilewidth);
		tmx_get_int_attr(attr, "tileheight",
				&cur_tmx->cur_tileset->tileheight);
	}

	/* TODO: Parse tilesets referenced in "source" attributes. */
}

static void
tmx_start_image(struct tmx *cur_tmx, const char **attr)
{
	char *source;
	char *path;

	if (cur_tmx->cur_tileset == NULL) {
		err(1, "Malformed TMX file");
	}

	source = NULL;
	foreach_tmx_attr (attr) {
		tmx_get_string_attr(attr, "source", source);
	}
	if (source == NULL) {
		err(1, "No \"source\" attribute found in \"image\" tag");
	}

	/* TODO: Move to end tag handler and check for "loadimage" property. */
	path = malloc(strlen(cur_tmx->dirname) + strlen(source) + 2);
	if (path == NULL) {
		err(1, "Failed to allocate resource path string");
	}
	sprintf(path, "%s/%s", cur_tmx->dirname, source);
	cur_tmx->cur_tileset->image = img_png_get(path);
	free(path);

	debug("  Found tileset with firstgid %d and source \"%s\"",
			cur_tmx->cur_tileset->firstgid, source);

	free(source);
}

static void
tmx_start_layer(struct tmx *cur_tmx, const char **attr)
{
	struct layer *new_layer;

	if (cur_tmx->map == NULL) {
		err(1, "Malformed TMX file");
	}

	new_layer = malloc(sizeof(*new_layer));
	if (new_layer == NULL) {
		err(1, "Failed to allocate layer");
	}
	memset(new_layer, 0, sizeof(*new_layer));

	if (cur_tmx->cur_layer == NULL) {
		cur_tmx->map->layers = new_layer;
	} else {
		cur_tmx->cur_layer->next = new_layer;
	}
	cur_tmx->cur_layer = new_layer;

	foreach_tmx_attr (attr) {
		tmx_get_string_attr(attr, "name", cur_tmx->cur_layer->name);
	}

	debug("  Found layer with name \"%s\"", cur_tmx->cur_layer->name);
}

static void
tmx_start_data(struct tmx *cur_tmx, const char **attr)
{
	if (cur_tmx->cur_layer == NULL) {
		err(1, "Malformed TMX file");
	}

	foreach_tmx_attr (attr) {
		if (strcmp(attr[0], "encoding") == 0) {
			if (strcmp(attr[1], "base64") == 0) {
				cur_tmx->data_encoding = TMX_DATA_ENC_BASE64;
			} else if (strcmp(attr[1], "csv") == 0) {
				cur_tmx->data_encoding = TMX_DATA_ENC_CSV;
			} else {
				err(1, "Unsupported data encoding in TMX file");
			}
		} else if (strcmp(attr[0], "compression") == 0) {
			if (strcmp(attr[1], "gzip") == 0) {
				cur_tmx->data_compression = TMX_DATA_COMP_GZIP;
			} else if (strcmp(attr[1], "zlib") == 0) {
				cur_tmx->data_compression = TMX_DATA_COMP_ZLIB;
			} else {
				err(1, "Unsupported compression in TMX file");
			}
		}
	}
}

static void XMLCALL
tmx_start(void *data, const char *el, const char **attr)
{
	struct tmx *cur_tmx;

	cur_tmx = (struct tmx *) data;

	if (strcmp(el, "map") == 0) {
		tmx_start_map(cur_tmx, attr);
		cur_tmx->parsing = TMX_PARSING_MAP;
	} else if (strcmp(el, "tileset") == 0) {
		tmx_start_tileset(cur_tmx, attr);
		cur_tmx->parsing = TMX_PARSING_TILESET;
	} else if (strcmp(el, "image") == 0) {
		tmx_start_image(cur_tmx, attr);
		cur_tmx->parsing = TMX_PARSING_IMAGE;
	} else if (strcmp(el, "layer") == 0) {
		tmx_start_layer(cur_tmx, attr);
		cur_tmx->parsing = TMX_PARSING_LAYER;
	} else if (strcmp(el, "data") == 0) {
		tmx_start_data(cur_tmx, attr);
		cur_tmx->parsing = TMX_PARSING_DATA;
	}

	/* TODO: Handle objectgroup, object, properties, and property tags. */
}

static void
tmx_end_data(struct tmx *cur_tmx)
{
	size_t decoded_len;
	size_t decomp_len;
	char *decoded_buf;
	char *decomp_buf;

	decoded_len = strlen(cur_tmx->layer_data);

	decomp_len = 4 * cur_tmx->map->width * cur_tmx->map->height;
	debug("  Expected map data size: %d", decomp_len);

	decoded_buf = malloc(decoded_len + 1);
	if (decoded_buf == NULL) {
		err(1, "Failed to allocate map layer data buffer");
	}

	if (cur_tmx->data_encoding == TMX_DATA_ENC_BASE64) {
		debug("  Decoding base 64 layer data...");
		base64_decode(cur_tmx->layer_data,
				decoded_buf, decoded_len + 1);
	}

	if (cur_tmx->data_compression == TMX_DATA_COMP_NONE) {
		debug("  Layer data already decompressed");
		decomp_buf = decoded_buf;
	} else if (cur_tmx->data_compression == TMX_DATA_COMP_ZLIB) {
		debug("  Decompressing layer data with zlib...");
		decomp_buf = malloc(decomp_len);
		if (decomp_buf == NULL) {
			err(1, "Failed to allocate map layer data buffer");
		}
		decompress(decoded_buf, decoded_len, decomp_buf, decomp_len);
		free(decoded_buf);
	} else if (cur_tmx->data_compression == TMX_DATA_COMP_GZIP) {
		debug("  Decompressing layer data with gzip...");
		decomp_buf = malloc(decomp_len);
		if (decomp_buf == NULL) {
			err(1, "Failed to allocate map layer data buffer");
		}
		decompress(decoded_buf, decoded_len, decomp_buf, decomp_len);
		free(decoded_buf);
	} else {
		/* This should never happen.  This branch exists only to silence
		 * GCC's maybe-uninitialized warning on decomp_buf below. */
		return;
	}

	free(cur_tmx->layer_data);

	cur_tmx->cur_layer->tiles = (Uint32 *) decomp_buf;
}

static void XMLCALL
tmx_end(void *data, const char *el)
{
	struct tmx *cur_tmx;

	cur_tmx = (struct tmx *) data;

	if (strcmp(el, "data") == 0) {
		tmx_end_data(cur_tmx);
	}

	cur_tmx->parsing = TMX_PARSING_NONE;
}

static void XMLCALL
tmx_data(void *data, const char *s, int len)
{
	struct tmx *cur_tmx;
	char *s_z;
	char *s_z_trimmed, *s_z_trimmed_end;

	cur_tmx = (struct tmx *) data;

	if (cur_tmx->parsing != TMX_PARSING_DATA) {
		return;
	}

	s_z = s_z_trimmed = strndup(s, len);

	while(isspace(*s_z_trimmed)) {
		++s_z_trimmed;
		--len;
	}
	if (*s_z_trimmed == '\0') {
		return;
	}
	s_z_trimmed_end = s_z_trimmed + len - 1;
	while (s_z_trimmed_end > s_z_trimmed && isspace(*s_z_trimmed_end)) {
		--s_z_trimmed_end;
	}
	*(s_z_trimmed_end + 1) = '\0';

	cur_tmx->layer_data = strdup(s_z_trimmed);

	free(s_z);
}

struct map *
tmx_load(const char *path)
{
	XML_Parser p;
	struct tmx cur_tmx;
	char *path_dup;
	FILE *tmx_fp;
	void *tmx_buf;
	size_t len;

	debug("Parsing TMX file \"%s\"...", path);

	p = XML_ParserCreate(NULL);
	if (p == NULL) {
		err(1, "Failed to create TMX parser");
	}

	XML_SetElementHandler(p, tmx_start, tmx_end);
	XML_SetCharacterDataHandler(p, tmx_data);

	memset(&cur_tmx, 0, sizeof(cur_tmx));
	path_dup = strdup(path);
	cur_tmx.dirname = dirname(path_dup);
	XML_SetUserData(p, &cur_tmx);

	tmx_fp = fopen(path, "rb");
	if (tmx_fp == NULL) {
		err(1, "Failed to open TMX file");
	}

	tmx_buf = XML_GetBuffer(p, 8192);
	if (tmx_buf == NULL) {
		err(1, "Failed to create TMX parse buffer");
	}

	while (!feof(tmx_fp)) {
		len = fread(tmx_buf, 1, 8192, tmx_fp);
		if (XML_ParseBuffer(p, len, feof(tmx_fp)) == XML_STATUS_ERROR) {
			err(1, "Failed to parse TMX file (%s)",
					XML_ErrorString(XML_GetErrorCode(p)));
		}
	}

	fclose(tmx_fp);

	free(path_dup);

	return cur_tmx.map;
}