#include <stdlib.h>
#include <assert.h>
#include <stdio.h>
#include <stdbool.h>
#include <ctype.h>

#include "stmd.h"
#include "scanners.h"
#include "uthash.h"

#define peek_at(i, n) (i)->data[n]

static void incorporate_line(strbuf *ln, int line_number, block** curptr);
static void finalize(block* b, int line_number);

static block* make_block(int tag, int start_line, int start_column)
{
	block* e;
	e = (block*) malloc(sizeof(block));
	e->tag = tag;
	e->open = true;
	e->last_line_blank = false;
	e->start_line = start_line;
	e->start_column = start_column;
	e->end_line = start_line;
	e->children = NULL;
	e->last_child = NULL;
	e->parent = NULL;
	e->top = NULL;
	e->attributes.refmap = NULL;
	strbuf_init(&e->string_content, 32);
	e->inline_content = NULL;
	e->next = NULL;
	e->prev = NULL;
	return e;
}

// Create a root document block.
extern block* make_document()
{
	block * e = make_block(document, 1, 1);
	reference * map = NULL;
	reference ** refmap;
	refmap = (reference**) malloc(sizeof(reference*));
	*refmap = map;
	e->attributes.refmap = refmap;
	e->top = e;
	return e;
}

// Returns true if line has only space characters, else false.
bool is_blank(strbuf *s, int offset)
{
	while (offset < s->size) {
		switch (s->ptr[offset]) {
			case '\n':
				return true;
			case ' ':
				offset++;
				break;
			default:
				return false;
		}
	}

	return true;
}

static inline bool can_contain(int parent_type, int child_type)
{
	return ( parent_type == document ||
			parent_type == block_quote ||
			parent_type == list_item ||
			(parent_type == list && child_type == list_item) );
}

static inline bool accepts_lines(int block_type)
{
	return (block_type == paragraph ||
			block_type == atx_header ||
			block_type == indented_code ||
			block_type == fenced_code);
}

static void add_line(block* block, chunk *ch, int offset)
{
	assert(block->open);
	strbuf_put(&block->string_content, ch->data + offset, ch->len - offset);
}

static void remove_trailing_blank_lines(strbuf *ln)
{
	int i;

	for (i = ln->size - 1; i >= 0; --i) {
		char c = ln->ptr[i];

		if (c != ' ' && c != '\t' && c != '\r' && c != '\n')
			break;
	}

	if (i < 0) {
		strbuf_clear(ln);
		return;
	}

	i = strbuf_strchr(ln, '\n', i);
	if (i >= 0)
		strbuf_truncate(ln, i);
}

// Check to see if a block ends with a blank line, descending
// if needed into lists and sublists.
static bool ends_with_blank_line(block* block)
{
	if (block->last_line_blank) {
		return true;
	}
	if ((block->tag == list || block->tag == list_item) && block->last_child) {
		return ends_with_blank_line(block->last_child);
	} else {
		return false;
	}
}

// Break out of all containing lists
static int break_out_of_lists(block ** bptr, int line_number)
{
	block * container = *bptr;
	block * b = container->top;
	// find first containing list:
	while (b && b->tag != list) {
		b = b->last_child;
	}
	if (b) {
		while (container && container != b) {
			finalize(container, line_number);
			container = container->parent;
		}
		finalize(b, line_number);
		*bptr = b->parent;
	}
	return 0;
}


static void finalize(block* b, int line_number)
{
	int firstlinelen;
	int pos;
	block* item;
	block* subitem;

	if (!b->open)
		return; // don't do anything if the block is already closed

	b->open = false;
	if (line_number > b->start_line) {
		b->end_line = line_number - 1;
	} else {
		b->end_line = line_number;
	}

	switch (b->tag) {
		case paragraph:
			pos = 0;
			while (strbuf_at(&b->string_content, 0) == '[' &&
					(pos = parse_reference(&b->string_content, b->top->attributes.refmap))) {

				strbuf_drop(&b->string_content, pos);
			}
			if (is_blank(&b->string_content, 0)) {
				b->tag = reference_def;
			}
			break;

		case indented_code:
			remove_trailing_blank_lines(&b->string_content);
			strbuf_putc(&b->string_content, '\n');
			break;

		case fenced_code:
			// first line of contents becomes info
			firstlinelen = strbuf_strchr(&b->string_content, '\n', 0);

			strbuf_init(&b->attributes.fenced_code_data.info, 0);
			strbuf_set(
				&b->attributes.fenced_code_data.info,
				b->string_content.ptr,
				firstlinelen
			);

			strbuf_drop(&b->string_content, firstlinelen + 1);

			strbuf_trim(&b->attributes.fenced_code_data.info);
			unescape_buffer(&b->attributes.fenced_code_data.info);
			break;

		case list: // determine tight/loose status
			b->attributes.list_data.tight = true; // tight by default
			item = b->children;

			while (item) {
				// check for non-final non-empty list item ending with blank line:
				if (item->last_line_blank && item->next) {
					b->attributes.list_data.tight = false;
					break;
				}
				// recurse into children of list item, to see if there are
				// spaces between them:
				subitem = item->children;
				while (subitem) {
					if (ends_with_blank_line(subitem) &&
							(item->next || subitem->next)) {
						b->attributes.list_data.tight = false;
						break;
					}
					subitem = subitem->next;
				}
				if (!(b->attributes.list_data.tight)) {
					break;
				}
				item = item->next;
			}

			break;

		default:
			break;
	}
}

// Add a block as child of another.  Return pointer to child.
extern block* add_child(block* parent,
		int block_type, int start_line, int start_column)
{
	assert(parent);

	// if 'parent' isn't the kind of block that can accept this child,
	// then back up til we hit a block that can.
	while (!can_contain(parent->tag, block_type)) {
		finalize(parent, start_line);
		parent = parent->parent;
	}

	block* child = make_block(block_type, start_line, start_column);
	child->parent = parent;
	child->top = parent->top;

	if (parent->last_child) {
		parent->last_child->next = child;
		child->prev = parent->last_child;
	} else {
		parent->children = child;
		child->prev = NULL;
	}
	parent->last_child = child;
	return child;
}

// Free a block list and any children.
extern void free_blocks(block* e)
{
	block * next;
	while (e != NULL) {
		next = e->next;
		free_inlines(e->inline_content);
		strbuf_free(&e->string_content);
		if (e->tag == fenced_code) {
			strbuf_free(&e->attributes.fenced_code_data.info);
		} else if (e->tag == document) {
			free_reference_map(e->attributes.refmap);
		}
		free_blocks(e->children);
		free(e);
		e = next;
	}
}

// Walk through block and all children, recursively, parsing
// string content into inline content where appropriate.
void process_inlines(block* cur, reference** refmap)
{
	switch (cur->tag) {
		case paragraph:
		case atx_header:
		case setext_header:
			cur->inline_content = parse_inlines(&cur->string_content, refmap);
			// MEM
			// strbuf_free(&cur->string_content);
			break;

		default:
			break;
	}

	block *child = cur->children;
	while (child != NULL) {
		process_inlines(child, refmap);
		child = child->next;
	}
}

// Attempts to parse a list item marker (bullet or enumerated).
// On success, returns length of the marker, and populates
// data with the details.  On failure, returns 0.
static int parse_list_marker(chunk *input, int pos, struct ListData ** dataptr)
{
	unsigned char c;
	int startpos;
	struct ListData * data;

	startpos = pos;
	c = peek_at(input, pos);

	if ((c == '*' || c == '-' || c == '+') && !scan_hrule(input, pos)) {
		pos++;
		if (!isspace(peek_at(input, pos))) {
			return 0;
		}
		data = malloc(sizeof(struct ListData));
		data->marker_offset = 0; // will be adjusted later
		data->list_type = bullet;
		data->bullet_char = c;
		data->start = 1;
		data->delimiter = period;
		data->tight = false;

	} else if (isdigit(c)) {
		int start = 0;

		do {
			start = (10 * start) + (peek_at(input, pos) - '0');
			pos++;
		} while (isdigit(peek_at(input, pos)));

		c = peek_at(input, pos);
		if (c == '.' || c == ')') {
			pos++;
			if (!isspace(peek_at(input, pos))) {
				return 0;
			}
			data = malloc(sizeof(struct ListData));
			data->marker_offset = 0; // will be adjusted later
			data->list_type = ordered;
			data->bullet_char = 0;
			data->start = start;
			data->delimiter = (c == '.' ? period : parens);
			data->tight = false;
		} else {
			return 0;
		}

	} else {
		return 0;
	}

	*dataptr = data;
	return (pos - startpos);
}

// Return 1 if list item belongs in list, else 0.
static int lists_match(struct ListData list_data,
		struct ListData item_data)
{
	return (list_data.list_type == item_data.list_type &&
			list_data.delimiter == item_data.delimiter &&
			// list_data.marker_offset == item_data.marker_offset &&
			list_data.bullet_char == item_data.bullet_char);
}

static void expand_tabs(strbuf *ob, const unsigned char *line, size_t size)
{
	size_t  i = 0, tab = 0;

	while (i < size) {
		size_t org = i;

		while (i < size && line[i] != '\t') {
			i++; tab++;
		}

		if (i > org)
			strbuf_put(ob, line + org, i - org);

		if (i >= size)
			break;

		do {
			strbuf_putc(ob, ' '); tab++;
		} while (tab % 4);

		i++;
	}
}

static block *finalize_document(block *document, int linenum)
{
	while (document != document->top) {
		finalize(document, linenum);
		document = document->parent;
	}

	finalize(document, linenum);
	process_inlines(document, document->attributes.refmap);

	return document;
}

extern block *stmd_parse_file(FILE *f)
{
	strbuf line = GH_BUF_INIT;
	unsigned char buffer[4096];
	int linenum = 1;
	block *document = make_document();

	while (fgets((char *)buffer, sizeof(buffer), f)) {
		expand_tabs(&line, buffer, strlen((char *)buffer));
		incorporate_line(&line, linenum, &document);
		strbuf_clear(&line);
		linenum++;
	}

	strbuf_free(&line);
	return finalize_document(document, linenum);
}

extern block *stmd_parse_document(const unsigned char *buffer, size_t len)
{
	strbuf line = GH_BUF_INIT;
	int linenum = 1;
	const unsigned char *end = buffer + len;
	block *document = make_document();

	while (buffer < end) {
		const unsigned char *eol = memchr(buffer, '\n', end - buffer);

		if (!eol) {
			expand_tabs(&line, buffer, end - buffer);
			buffer = end;
		} else {
			expand_tabs(&line, buffer, (eol - buffer) + 1);
			buffer += (eol - buffer) + 1;
		}

		incorporate_line(&line, linenum, &document);
		strbuf_clear(&line);
		linenum++;
	}

	strbuf_free(&line);
	return finalize_document(document, linenum);
}

static void chop_trailing_hashtags(chunk *ch)
{
	int n;

	chunk_rtrim(ch);
	n = ch->len - 1;

	// if string ends in #s, remove these:
	while (n >= 0 && peek_at(ch, n) == '#')
		n--;

	// the last # was escaped, so we include it.
	if (n >= 0 && peek_at(ch, n) == '\\')
		n++;

	ch->len = n + 1;
}

// Process one line at a time, modifying a block.
static void incorporate_line(strbuf *line, int line_number, block** curptr)
{
	block* last_matched_container;
	int offset = 0;
	int matched = 0;
	int lev = 0;
	int i;
	struct ListData * data = NULL;
	bool all_matched = true;
	block* container;
	block* cur = *curptr;
	bool blank = false;
	int first_nonspace;
	int indent;
	chunk input;

	input.data = line->ptr;
	input.len = line->size;

	// container starts at the document root.
	container = cur->top;

	// for each containing block, try to parse the associated line start.
	// bail out on failure:  container will point to the last matching block.

	while (container->last_child && container->last_child->open) {
		container = container->last_child;

		first_nonspace = offset;
		while (peek_at(&input, first_nonspace) == ' ') {
			first_nonspace++;
		}

		indent = first_nonspace - offset;
		blank = peek_at(&input, first_nonspace) == '\n';

		if (container->tag == block_quote) {
			matched = indent <= 3 && peek_at(&input, first_nonspace) == '>';
			if (matched) {
				offset = first_nonspace + 1;
				if (peek_at(&input, offset) == ' ')
					offset++;
			} else {
				all_matched = false;
			}

		} else if (container->tag == list_item) {

			if (indent >= container->attributes.list_data.marker_offset +
					container->attributes.list_data.padding) {
				offset += container->attributes.list_data.marker_offset +
					container->attributes.list_data.padding;
			} else if (blank) {
				offset = first_nonspace;
			} else {
				all_matched = false;
			}

		} else if (container->tag == indented_code) {

			if (indent >= CODE_INDENT) {
				offset += CODE_INDENT;
			} else if (blank) {
				offset = first_nonspace;
			} else {
				all_matched = false;
			}

		} else if (container->tag == atx_header ||
				container->tag == setext_header) {

			// a header can never contain more than one line
			all_matched = false;

		} else if (container->tag == fenced_code) {

			// skip optional spaces of fence offset
			i = container->attributes.fenced_code_data.fence_offset;
			while (i > 0 && peek_at(&input, offset) == ' ') {
				offset++;
				i--;
			}

		} else if (container->tag == html_block) {

			if (blank) {
				all_matched = false;
			}

		} else if (container->tag == paragraph) {

			if (blank) {
				container->last_line_blank = true;
				all_matched = false;
			}

		}

		if (!all_matched) {
			container = container->parent;  // back up to last matching block
			break;
		}
	}

	last_matched_container = container;

	// check to see if we've hit 2nd blank line, break out of list:
	if (blank && container->last_line_blank) {
		break_out_of_lists(&container, line_number);
	}

	// unless last matched container is code block, try new container starts:
	while (container->tag != fenced_code && container->tag != indented_code &&
			container->tag != html_block) {

		first_nonspace = offset;
		while (peek_at(&input, first_nonspace) == ' ')
			first_nonspace++;

		indent = first_nonspace - offset;
		blank = peek_at(&input, first_nonspace) == '\n';

		if (indent >= CODE_INDENT) {
			if (cur->tag != paragraph && !blank) {
				offset += CODE_INDENT;
				container = add_child(container, indented_code, line_number, offset + 1);
			} else { // indent > 4 in lazy line
				break;
			}

		} else if (peek_at(&input, first_nonspace) == '>') {

			offset = first_nonspace + 1;
			// optional following character
			if (peek_at(&input, offset) == ' ')
				offset++;
			container = add_child(container, block_quote, line_number, offset + 1);

		} else if ((matched = scan_atx_header_start(&input, first_nonspace))) {

			offset = first_nonspace + matched;
			container = add_child(container, atx_header, line_number, offset + 1);

			int hashpos = chunk_strchr(&input, '#', first_nonspace);
			int level = 0;

			while (peek_at(&input, hashpos) == '#') {
				level++;
				hashpos++;
			}
			container->attributes.header_level = level;

		} else if ((matched = scan_open_code_fence(&input, first_nonspace))) {

			container = add_child(container, fenced_code, line_number, first_nonspace + 1);
			container->attributes.fenced_code_data.fence_char = peek_at(&input, first_nonspace);
			container->attributes.fenced_code_data.fence_length = matched;
			container->attributes.fenced_code_data.fence_offset = first_nonspace - offset;
			offset = first_nonspace + matched;

		} else if ((matched = scan_html_block_tag(&input, first_nonspace))) {

			container = add_child(container, html_block, line_number, first_nonspace + 1);
			// note, we don't adjust offset because the tag is part of the text

		} else if (container->tag == paragraph &&
				(lev = scan_setext_header_line(&input, first_nonspace)) &&
				// check that there is only one line in the paragraph:
				strbuf_strrchr(&container->string_content, '\n',
					strbuf_len(&container->string_content) - 2) < 0) {

			container->tag = setext_header;
			container->attributes.header_level = lev;
			offset = input.len - 1;

		} else if (!(container->tag == paragraph && !all_matched) &&
				(matched = scan_hrule(&input, first_nonspace))) {

			// it's only now that we know the line is not part of a setext header:
			container = add_child(container, hrule, line_number, first_nonspace + 1);
			finalize(container, line_number);
			container = container->parent;
			offset = input.len - 1;

		} else if ((matched = parse_list_marker(&input, first_nonspace, &data))) {

			// compute padding:
			offset = first_nonspace + matched;
			i = 0;
			while (i <= 5 && peek_at(&input, offset + i) == ' ') {
				i++;
			}
			// i = number of spaces after marker, up to 5
			if (i >= 5 || i < 1 || peek_at(&input, offset) == '\n') {
				data->padding = matched + 1;
				if (i > 0) {
					offset += 1;
				}
			} else {
				data->padding = matched + i;
				offset += i;
			}

			// check container; if it's a list, see if this list item
			// can continue the list; otherwise, create a list container.

			data->marker_offset = indent;

			if (container->tag != list ||
					!lists_match(container->attributes.list_data, *data)) {
				container = add_child(container, list, line_number,
						first_nonspace + 1);
				container->attributes.list_data = *data;
			}

			// add the list item
			container = add_child(container, list_item, line_number,
					first_nonspace + 1);
			/* TODO: static */
			container->attributes.list_data = *data;
			free(data);

		} else {
			break;
		}

		if (accepts_lines(container->tag)) {
			// if it's a line container, it can't contain other containers
			break;
		}
	}

	// what remains at offset is a text line.  add the text to the
	// appropriate container.

	first_nonspace = offset;
	while (peek_at(&input, first_nonspace) == ' ')
		first_nonspace++;

	indent = first_nonspace - offset;
	blank = peek_at(&input, first_nonspace) == '\n';

	// block quote lines are never blank as they start with >
	// and we don't count blanks in fenced code for purposes of tight/loose
	// lists or breaking out of lists.  we also don't set last_line_blank
	// on an empty list item.
	container->last_line_blank = (blank &&
			container->tag != block_quote &&
			container->tag != fenced_code &&
			!(container->tag == list_item &&
				container->children == NULL &&
				container->start_line == line_number));

	block *cont = container;
	while (cont->parent) {
		cont->parent->last_line_blank = false;
		cont = cont->parent;
	}

	if (cur != last_matched_container &&
			container == last_matched_container &&
			!blank &&
			cur->tag == paragraph &&
			strbuf_len(&cur->string_content) > 0) {

		add_line(cur, &input, offset);

	} else { // not a lazy continuation

		// finalize any blocks that were not matched and set cur to container:
		while (cur != last_matched_container) {
			finalize(cur, line_number);
			cur = cur->parent;
			assert(cur != NULL);
		}

		if (container->tag == indented_code) {

			add_line(container, &input, offset);

		} else if (container->tag == fenced_code) {
			matched = 0;

			if (indent <= 3 &&
				peek_at(&input, first_nonspace) == container->attributes.fenced_code_data.fence_char) {
				int fence_len = scan_close_code_fence(&input, first_nonspace);
				if (fence_len > container->attributes.fenced_code_data.fence_length)
					matched = 1;
			}

			if (matched) {
				// if closing fence, don't add line to container; instead, close it:
				finalize(container, line_number);
				container = container->parent; // back up to parent
			} else {
				add_line(container, &input, offset);
			}

		} else if (container->tag == html_block) {

			add_line(container, &input, offset);

		} else if (blank) {

			// ??? do nothing

		} else if (container->tag == atx_header) {

			chop_trailing_hashtags(&input);
			add_line(container, &input, first_nonspace);
			finalize(container, line_number);
			container = container->parent;

		} else if (accepts_lines(container->tag)) {

			add_line(container, &input, first_nonspace);

		} else if (container->tag != hrule && container->tag != setext_header) {

			// create paragraph container for line
			container = add_child(container, paragraph, line_number, first_nonspace + 1);
			add_line(container, &input, first_nonspace);

		} else {
			assert(false);
		}

		*curptr = container;
	}
}