#include <stdio.h>
#include <string.h>
#include <mysql/mysql.h>

#define NAME        "sql_printf"
#define N_ARGS      1
#define BLOCK_SIZE  1024

extern "C" {

typedef struct {
	int * org_type;
	char * data;
	unsigned long len;
	unsigned long alloc;
}
Buffer;

static void buffer_append_len(Buffer *buffer, const char *string, unsigned long len) {
	if (!string) return;
	unsigned long new_len = buffer->len + len;

	if (new_len > buffer->alloc) {
		buffer->alloc = new_len + BLOCK_SIZE - (new_len % BLOCK_SIZE);
		buffer->data = (char *) realloc(buffer->data, sizeof(char) * buffer->alloc);
	}

	strncpy(&buffer->data[buffer->len], string, len);
	buffer->len = new_len;
}

static void buffer_append(Buffer *buffer, const char *string) {
	if (!string) return;
	buffer_append_len(buffer, string, strlen(string));
}

char * sql_printf(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *error) {
	unsigned int i = 1;
	unsigned long j = 0;
	Buffer *buffer = (Buffer *) initid->ptr;
	char *format = args->args[0];
	
	if (!format) {
		*is_null = 1;
		return NULL;
	}

	while (1) {
		const char *delimiter = NULL;
		unsigned long aux = j;

		while (j < args->lengths[0] && format[j] != '%')
			j++;

		buffer_append_len(buffer, &format[aux], j - aux);

		if (j == args->lengths[0])
			break;
			
		char c = format[j+1];
		j += 2;
	
		switch (c) {
			case 't':
				delimiter = "`";
				break;
			case 'v':
				if (buffer->org_type[i] == STRING_RESULT)
					delimiter = "'";
				break;
			case 's':
				break;
			case '%':
				buffer_append(buffer, "%");
				continue;
			default:
				*error = 1;
				return NULL;
		}
		
		if (i >= args->arg_count) {
			*error = 1;
			return NULL;
		}

		char *arg = args->args[i];

		if (arg != NULL) {
			buffer_append(buffer, delimiter);
			buffer_append_len(buffer, arg, args->lengths[i]);
			buffer_append(buffer, delimiter);
		} else
			buffer_append(buffer, "NULL");

		i++;
	}

	*length = buffer->len;
	return buffer->data;
}

bool sql_printf_init(UDF_INIT *initid, UDF_ARGS *args, char *message) {
	if (args->arg_count >= N_ARGS) {
		unsigned int i;
		Buffer *buffer = (Buffer *) malloc(sizeof(Buffer));
		buffer->org_type = (int *) malloc(sizeof(int) * args->arg_count);
		buffer->alloc = BLOCK_SIZE;
		buffer->data = (char *) malloc(sizeof(char) * buffer->alloc);
		buffer->len = 0;
		
		for (i = 0; i < args->arg_count; i++) {
			buffer->org_type[i] = args->arg_type[i];
			args->arg_type[i] = STRING_RESULT;
		}

		initid->ptr = (char *) buffer;
		initid->maybe_null = 1;
		initid->const_item = 0;
		return 0;
	} else {
		sprintf(message, "%s must have at least %d parameters", NAME, N_ARGS);
		return 1;
	}
}

void sql_printf_deinit(UDF_INIT *initid) {
	Buffer *buffer = (Buffer *) initid->ptr;
	free(buffer->org_type);
	free(buffer->data);
	free(buffer);
}

}