#include "bf_compiler.h"

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <libtcc.h>

struct str_buffer {
	char *data;
	size_t len;
	size_t capacity;
};

static void str_buffer_init(struct str_buffer *buffer, size_t capacity)
{
	buffer->data = malloc(capacity);
	assert(buffer->data != NULL);
	buffer->len = 0;
	buffer->capacity = capacity;
}

static void str_buffer_deinit(struct str_buffer *buffer)
{
	free(buffer->data);
	buffer->data = NULL;
	buffer->capacity = 0;
	buffer->len = 0;
}

static void str_buffer_append_with_len(struct str_buffer *buffer, const char *text, size_t text_len)
{
	if (buffer->len + text_len > buffer->capacity) {
		while (buffer->len + text_len > buffer->capacity) {
			buffer->capacity *= 2;
		}

		buffer->data = realloc(buffer->data, buffer->capacity);
		assert(buffer->data != NULL);
	}

	memcpy(buffer->data + buffer->len, text, text_len);
	buffer->len += text_len;
}

static void str_buffer_append(struct str_buffer *buffer, const char *text)
{
	str_buffer_append_with_len(buffer, text, strlen(text));
}

static int bf_compiler_compile_tinycc(struct bf_compiler *compiler, const char *output_filename, const char *program, size_t program_len)
{
	struct str_buffer c_program = { 0 };
	str_buffer_init(&c_program, 128);

	int rc = -1;
	TCCState *state = tcc_new();
	if (!state) {
		goto err;
	}

	const char *cell_type = NULL;
	if (compiler->cell_size == 8) {
		cell_type = "uint8_t";
	} else if (compiler->cell_size == 16) {
		cell_type = "uint16_t";
	} else if (compiler->cell_size == 32) {
		cell_type = "uint32_t";
	} else {
		return -1;
	}

	char line_buffer[256] = { 0 };

	str_buffer_append(&c_program, "#include <inttypes.h>\n");
	str_buffer_append(&c_program, "#include <stdlib.h>\n");
	str_buffer_append(&c_program, "#include <assert.h>\n");

	snprintf(line_buffer, sizeof(line_buffer), "typedef %s cell_t;\n", cell_type);
	str_buffer_append(&c_program, line_buffer);

	str_buffer_append(&c_program, "int main()\n");
	str_buffer_append(&c_program, "{\n");

	snprintf(line_buffer, sizeof(line_buffer), "size_t data_len = %d;\n", compiler->data_len);
	str_buffer_append(&c_program, line_buffer);

	str_buffer_append(&c_program, "cell_t data_pointer = 0;\n");
	str_buffer_append(&c_program, "cell_t *data = calloc(data_len, sizeof(cell_t));\n");
	str_buffer_append(&c_program, "assert(data != NULL);\n");

	for (int i = 0; i < program_len; i++) {
		char inst = program[i];

		if (inst == '>') {
			str_buffer_append(&c_program, "data_pointer++;\n");
		} else if (inst == '<') {
			str_buffer_append(&c_program, "data_pointer--;\n");
		} else if (inst == '+') {
			str_buffer_append(&c_program, "data[data_pointer]++;\n");
		} else if (inst == '-') {
			str_buffer_append(&c_program, "data[data_pointer]--;\n");
		} else if (inst == '.') {
			str_buffer_append(&c_program, "putchar(data[data_pointer]); fflush(0);\n");
		} else if (inst == ',') {
			str_buffer_append(&c_program, "data[data_pointer] = getchar();\n");
		} else if (inst == '[') {
			str_buffer_append(&c_program, "while (data[data_pointer] != 0) {\n");
		} else if (inst == ']') {
			str_buffer_append(&c_program, "}\n");
		}
	}

	str_buffer_append(&c_program, "free(data);\n");
	str_buffer_append(&c_program, "return 0;\n");
	str_buffer_append(&c_program, "}\n");
	str_buffer_append_with_len(&c_program, "\0", 1);

	tcc_set_output_type(state, TCC_OUTPUT_EXE);
	tcc_set_options(state, "-w");
	if (tcc_compile_string(state, c_program.data) == -1) {
		goto err;
	}

	if (tcc_output_file(state, output_filename)) {
		goto err;
	}

	rc = 0;
err:
	tcc_delete(state);
	str_buffer_deinit(&c_program);
	return rc;
}