/*
 Author: José Bollo <jobol@nonadev.net>
 Author: José Bollo <jose.bollo@iot.bzh>

 https://gitlab.com/jobol/mustach

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
*/

#define _GNU_SOURCE

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>

#include "mustach.h"

#define NAME_LENGTH_MAX   1024
#define DEPTH_MAX         256

static int getpartial(struct mustach_itf *itf, void *closure, const char *name, char **result)
{
	int rc;
	FILE *file;
	size_t size;

	*result = NULL;
	file = open_memstream(result, &size);
	if (file == NULL)
		rc = MUSTACH_ERROR_SYSTEM;
	else {
		rc = itf->put(closure, name, 0, file);
		if (rc == 0)
			/* adds terminating null */
			rc = fputc(0, file) ? MUSTACH_ERROR_SYSTEM : 0;
		fclose(file);
		if (rc < 0) {
			free(*result);
			*result = NULL;
		}
	}
	return rc;
}

static int process(const char *template, struct mustach_itf *itf, void *closure, FILE *file, const char *opstr, const char *clstr)
{
	char name[NAME_LENGTH_MAX + 1], *partial, c;
	const char *beg, *term;
	struct { const char *name, *again; size_t length; int emit, entered; } stack[DEPTH_MAX];
	size_t oplen, cllen, len, l;
	int depth, rc, emit;

	emit = 1;
	oplen = strlen(opstr);
	cllen = strlen(clstr);
	depth = 0;
	for(;;) {
		beg = strstr(template, opstr);
		if (beg == NULL) {
			/* no more mustach */
			if (emit)
				fwrite(template, strlen(template), 1, file);
			return depth ? MUSTACH_ERROR_UNEXPECTED_END : 0;
		}
		if (emit)
			fwrite(template, (size_t)(beg - template), 1, file);
		beg += oplen;
		term = strstr(beg, clstr);
		if (term == NULL)
			return MUSTACH_ERROR_UNEXPECTED_END;
		template = term + cllen;
		len = (size_t)(term - beg);
		c = *beg;
		switch(c) {
		case '!':
		case '=':
			break;
		case '{':
			for (l = 0 ; clstr[l] == '}' ; l++);
			if (clstr[l]) {
				if (!len || beg[len-1] != '}')
					return MUSTACH_ERROR_BAD_UNESCAPE_TAG;
				len--;
			} else {
				if (term[l] != '}')
					return MUSTACH_ERROR_BAD_UNESCAPE_TAG;
				template++;
			}
			c = '&';
			/*@fallthrough@*/
		case '^':
		case '#':
		case '/':
		case '&':
		case '>':
#if !defined(NO_EXTENSION_FOR_MUSTACH) && !defined(NO_COLON_EXTENSION_FOR_MUSTACH)
		case ':':
#endif
			beg++; len--;
		default:
			while (len && isspace(beg[0])) { beg++; len--; }
			while (len && isspace(beg[len-1])) len--;
			if (len == 0)
				return MUSTACH_ERROR_EMPTY_TAG;
			if (len > NAME_LENGTH_MAX)
				return MUSTACH_ERROR_TAG_TOO_LONG;
			memcpy(name, beg, len);
			name[len] = 0;
			break;
		}
		switch(c) {
		case '!':
			/* comment */
			/* nothing to do */
			break;
		case '=':
			/* defines separators */
			if (len < 5 || beg[len - 1] != '=')
				return MUSTACH_ERROR_BAD_SEPARATORS;
			beg++;
			len -= 2;
			for (l = 0; l < len && !isspace(beg[l]) ; l++);
			if (l == len)
				return MUSTACH_ERROR_BAD_SEPARATORS;
			opstr = strndupa(beg, l);
			while (l < len && isspace(beg[l])) l++;
			if (l == len)
				return MUSTACH_ERROR_BAD_SEPARATORS;
			clstr = strndupa(beg + l, len - l);
			oplen = strlen(opstr);
			cllen = strlen(clstr);
			break;
		case '^':
		case '#':
			/* begin section */
			if (depth == DEPTH_MAX)
				return MUSTACH_ERROR_TOO_DEPTH;
			rc = emit;
			if (rc) {
				rc = itf->enter(closure, name);
				if (rc < 0)
					return rc;
			}
			stack[depth].name = beg;
			stack[depth].again = template;
			stack[depth].length = len;
			stack[depth].emit = emit;
			stack[depth].entered = rc;
			if ((c == '#') == (rc == 0))
				emit = 0;
			depth++;
			break;
		case '/':
			/* end section */
			if (depth-- == 0 || len != stack[depth].length || memcmp(stack[depth].name, name, len))
				return MUSTACH_ERROR_CLOSING;
			rc = emit && stack[depth].entered ? itf->next(closure) : 0;
			if (rc < 0)
				return rc;
			if (rc) {
				template = stack[depth++].again;
			} else {
				emit = stack[depth].emit;
				if (emit && stack[depth].entered)
					itf->leave(closure);
			}
			break;
		case '>':
			/* partials */
			if (emit) {
				rc = getpartial(itf, closure, name, &partial);
				if (rc == 0) {
					rc = process(partial, itf, closure, file, opstr, clstr);
					free(partial);
				}
				if (rc < 0)
					return rc;
			}
			break;
		default:
			/* replacement */
			if (emit) {
				rc = itf->put(closure, name, c != '&', file);
				if (rc < 0)
					return rc;
			}
			break;
		}
	}
}

int fmustach(const char *template, struct mustach_itf *itf, void *closure, FILE *file)
{
	int rc = itf->start ? itf->start(closure) : 0;
	if (rc == 0)
		rc = process(template, itf, closure, file, "{{", "}}");
	return rc;
}

int fdmustach(const char *template, struct mustach_itf *itf, void *closure, int fd)
{
	int rc;
	FILE *file;

	file = fdopen(fd, "w");
	if (file == NULL) {
		rc = MUSTACH_ERROR_SYSTEM;
		errno = ENOMEM;
	} else {
		rc = fmustach(template, itf, closure, file);
		fclose(file);
	}
	return rc;
}

int mustach(const char *template, struct mustach_itf *itf, void *closure, char **result, size_t *size)
{
	int rc;
	FILE *file;
	size_t s;

	*result = NULL;
	if (size == NULL)
		size = &s;
	file = open_memstream(result, size);
	if (file == NULL) {
		rc = MUSTACH_ERROR_SYSTEM;
		errno = ENOMEM;
	} else {
		rc = fmustach(template, itf, closure, file);
		if (rc == 0)
			/* adds terminating null */
			rc = fputc(0, file) ? MUSTACH_ERROR_SYSTEM : 0;
		fclose(file);
		if (rc >= 0)
			/* removes terminating null of the length */
			(*size)--;
		else {
			free(*result);
			*result = NULL;
			*size = 0;
		}
	}
	return rc;
}