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

#include "doc.h"
#include "err.h"

/* initialization / destruction */

void doc_init(struct doc *d) {
	buf_init(&d->txt, sizeof(struct doc_line));
	buf_init(&d->lnk, 1);
	d->txt.sz = sizeof(struct doc_line);
	*(struct doc_line *)d->txt.buf = (struct doc_line) {
		.prev = 0,
		.link = DOC_LINK_NONE,
		.len = 0,
	};
	d->latest = 0;
	d->linkc = 0;
}

void doc_fini(struct doc *d) {
	buf_free(&d->txt);
	buf_free(&d->lnk);
}

/* line creation */

void doc_new_line(struct doc *d) {
	buf_grow(&d->txt, sizeof(struct doc_line));
	*(struct doc_line *)&d->txt.buf[d->txt.sz] = (struct doc_line) {
		.prev = ((struct doc_line *)&d->txt.buf[d->latest])->len,
		.link = DOC_LINK_NONE,
		.len = 0
	};
	d->latest = d->txt.sz;
	d->txt.sz += sizeof(struct doc_line);
}

void doc_add_line(struct doc *d, const char *s) {
	doc_add_text(d, s);
	doc_new_line(d);
}

void doc_add_text(struct doc *d, const char *s) {
	doc_add_textn(d, s, strlen(s));
}

void doc_add_textn(struct doc *d, const char *s, size_t n) {
	buf_grow(&d->txt, n);
	memcpy(&d->txt.buf[d->txt.sz], s, n);
	struct doc_line *dl = (struct doc_line *)&d->txt.buf[d->latest];
	d->txt.sz += n;
	dl->len += n;
}

unsigned short doc_add_link(struct doc *d, const char *url) {
	buf_cat(&d->lnk, url, strlen(url) + 1);
	return d->linkc++;
}

void doc_set_link(struct doc *d, unsigned short lnk) {
	struct doc_line *l = doc_line_at(d, d->latest);
	l->link = lnk;
}

/* line navigation */

struct doc_line *doc_line_at(struct doc *d, size_t ofs) {
	return (struct doc_line *)&d->txt.buf[ofs];
}

int doc_line_prev(struct doc *d, size_t *ofs) {
	size_t n = doc_line_at(d, *ofs)->prev + sizeof(struct doc_line);
	if (*ofs >= n) {
		*ofs -= n;
		return 0;
	} else {
		return -1;
	}
}

int doc_line_next(struct doc *d, size_t *ofs) {
	size_t n = doc_line_at(d, *ofs)->len + sizeof(struct doc_line);
	if (*ofs + n < d->txt.sz) {
		*ofs += n;
		return 0;
	} else {
		return -1;
	}
}

const char *doc_get_link(struct doc *d, unsigned short lnk) {
	size_t l = 1;
	for (size_t i = 0; i < d->lnk.sz; i++) {
		if (l == lnk) return &d->lnk.buf[i];
		if (d->lnk.buf[i] == 0) l++;
	}
	return NULL;
}