#include <cassert>
#include <cmath>
#include <cstdlib>
#include <cstdio>
#include <cstring>

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
#include "aixlog.hpp"

#include "util.h"


#define PALETTE_ROWS 16
#define PALETTE_COLUMNS 16
#define PALETTE_BORDER 1
const uint MAX_FILESIZE = 2 * 1024 * 1024; // 2MB
const uint MAX_STRING_LENGTH = 1024;


//-----------------
// C Strings

const char*
utilBaseName(const char* path_str)
{
	assert(std::strlen(path_str) < MAX_STRING_LENGTH);
	const char* output = std::strrchr(path_str, '/');
	if (output)
		return output;
	else
		return path_str;
}

bool
utilCopyCStr(char* dest, const char* src, uint max_len)
{
	assert(std::strlen(src) < MAX_STRING_LENGTH && max_len <= MAX_STRING_LENGTH);
	if (std::strlen(src) + 1 > max_len)
		return false;

	std::memcpy(dest, src, std::strlen(src) + 1);
	return true;
}

bool
utilConcatPath(char* out, const char* base_dir, const char* file_name, uint max_len)
{
	size_t l1 = std::strlen(base_dir);
	size_t l2 = std::strlen(file_name);
	size_t padded = l1 + l2 + 2; // NOTE: null term + '/'

	if (padded <= MAX_STRING_LENGTH && padded <= max_len) {
		int c = std::snprintf(out, padded, "%s/%s", base_dir, file_name);
		if (c > 0)
			return true;
		else
			return false;
	}

	return false;
}

bool
utilMatchPrefix(const char* lhs, const char* rhs, int sz)
{
	int rc = strncmp(lhs, rhs, sz);
	return (rc >= 0);
}

//-----------------
// Memory allocation

void *
utilLogAlloc(uint item_count, uint type_size, const char* file_name, const int line)
{
	assert(item_count > 0); // that was a fun bug

	void* mem = std::calloc(item_count, type_size);

	if (mem == nullptr) {
		LOG(ERROR) << "Memory allocation failed, called from "
					<< file_name << ":" << line;
	}

	assert(mem != nullptr); // might as well stop execution here

	return mem;
}

void utilSafeFree(const void* mem)
{
	if (mem != nullptr) {
		std::free((void *) mem);
		mem = nullptr;
	}
}

//-----------------
// File I/O

// TODO: don't use ftell() to get filesize
// 	https://wiki.sei.cmu.edu/confluence/display/c/FIO19-C.+Do+not+use+fseek%28%29+and+ftell%28%29+to+compute+the+size+of+a+regular+file
char *
utilDumpTextFile(const char* filename)
{
	LOG(INFO) << "loading filename, " << filename << "\n";
	std::FILE* fp = std::fopen(filename, "rt");
	assert(fp);

	std::fseek(fp, 0, SEEK_END);
	uint length = std::ftell(fp);
	std::fseek(fp, 0, SEEK_SET);
	assert(length < MAX_FILESIZE);
	// TODO: check error codes for fseek and ftell

	char* buf = UTIL_ALLOC(length, char);
	assert(buf);

	std::fread(buf, sizeof(char), length, fp);
	// TODO: check fp w/ ferror() here

	return buf;
}

// TODO: might want to do the base_dir concat in this function to prevent clobbering
//	user files on accident
bool
utilWriteTextFile(const char* filename, const char* text)
{
	size_t text_len = std::strlen(text);

	if (text_len >= MAX_FILESIZE) {
		LOG(ERROR) << "that string is too big\n";
		return false;
	}

	std::FILE* fp = fopen(filename, "wt");
	if (fp) {
		size_t written = fwrite(text, sizeof(char), text_len, fp);
		fclose(fp);
		if (written == text_len) {
			LOG(DEBUG) << "successfuly wrote " << written << " bytes\n";
			return true;
		} else {
			LOG(ERROR) << "error writing to file: " << filename << "\n";
			return false;
		}
	}

	LOG(DEBUG) << text << "\n";
	return false;
}

//-----------------
// utilImage

util_image
utilLoadImage(const char* base_dir, const char* filename)
{
	const uint max_path = 256; // NOTE: util_image.file_path is char[256]
	const char* base_name = utilBaseName(filename);
	// NOTE: +1 for '/' char, +1 for null
	uint l = std::strlen(base_dir) + std::strlen(base_name) + 2;
	assert(l < max_path);
	char full_path[l];
	std::memcpy(full_path, base_dir, std::strlen(base_dir) + 1);
	std::strcat(std::strcat(full_path, "/"), base_name);
	LOG(INFO) << "Loading Image: " << full_path << "\n";

	util_image image;
	std::memcpy(image.file_path, full_path, std::strlen(full_path) + 1);
	stbi_set_flip_vertically_on_load(1);
	image.pixels = stbi_load(full_path, &image.w, &image.h, &image.num_channels, 0);
	image.bits_per_channel = 8;
	image.data_len = image.w * image.h * image.num_channels; // NOTE: assumes 8 bits per channel

	if (image.pixels == 0) {
		LOG(ERROR) << stbi_failure_reason() << "\n";
		utilFreeImage(image);
		return image;
	}

	LOG(INFO) << "Image properties, data_len: " << image.data_len
		<< ", width: " << image.w << ", height: " << image.h << "\n";

	return image;
}

void
utilFreeImage(util_image image)
{
	image.w = image.h = image.data_len = 0;
	image.bits_per_channel = 8;
	image.num_channels = 4;
	std::memset(image.file_path, 0, std::strlen(image.file_path) + 1);
	utilSafeFree(image.pixels);
}

// need to init default values from scene file, or finally make default config?
v2f
utilGetPaletteCoords(util_image& palette_image, uint color_index)
{
	v2i tex_coords;
	v2f normalized;

	if (PALETTE_ROWS * PALETTE_COLUMNS < color_index) {
		LOG(ERROR) << "index out of range\n";
		return normalized;
	}

	if (palette_image.pixels == nullptr) {
		LOG(ERROR) << "palatte image not loaded\n";
		return normalized;
	}

	// NOTE: we're aiming to sample near the middle of the palette 'square' so GL_NEAREST
	//		doesn't try to sample the border color
	v2i palette_square;
	palette_square.x = palette_image.w / PALETTE_ROWS;
	palette_square.y = palette_image.h / PALETTE_COLUMNS;
	uint v_row = (uint) std::floor(color_index / PALETTE_ROWS);
	uint u_column = color_index % PALETTE_ROWS;
	tex_coords.x = u_column * palette_square.x + palette_square.x / 2;
	tex_coords.y = v_row * palette_square.y + palette_square.y / 2;
	// NOTE: flip y coord
	tex_coords.y = palette_image.h - tex_coords.y;

	normalized.x = (float) tex_coords.x / palette_image.w;
	normalized.y = (float) tex_coords.y / palette_image.h;

	return normalized;
}