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

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

/* text */

static struct {
	char *buf;
	size_t len, cap;
} txt;

void txt_init(void) {
	txt.buf = malloc(1);
	if (!txt.buf) efatal("txt_init");
	txt.buf[0] = 0;
	txt.len = 0;
	txt.cap = 1;
}

void txt_fini(void) {
	free(txt.buf);
}

void txt_grow(size_t n) {
	size_t cap = txt.cap;
	size_t len = txt.len + n;
	if (cap < len) {
		while (cap < len) cap <<= 1;
		char *s = realloc(txt.buf, cap);
		if (!s) efatal("txt_grow");
		txt.cap = cap;
		txt.buf = s;
	}
}

/* docs */

struct doc {
	size_t ofs, len, idx;
};

#define DOC_MAX 32

static struct doc docv[DOC_MAX] = {
	{
		 
		.ofs = 0,
		.len = 0,
		.idx = 0
	}
};

static size_t docn = 0, doci = 0;

void doc_pop(void) {
	if (docn > 0) {
		docn--;
		if (doci > 0) doci--;
	}
}

void doc_shift(void) {
	if (docn > 0) {
		docn--;
		memmove(txt.buf, txt.buf + docv[0].len, txt.len - docv[0].len);
		memmove(&docv[0], &docv[1], docn * sizeof(struct doc));
		docv[0].ofs = 0;
		for (int i = 1; i < docn; i++) {
			docv[i].idx = docv[i - 1].ofs + (docv[i].idx - docv[i].ofs);
			docv[i].ofs = docv[i - 1].ofs + docv[i - 1].len;
		}
		if (docn > 0 && doci >= docn) doci = docn - 1;
	}
}

void doc_new(void) {
	while (docn >= DOC_MAX) {
		doc_shift();
	}
	if (doci < docn) {
		txt.len = docv[doci].ofs;
		docn = doci;
	}
	memset(&docv[docn], 0, sizeof(struct doc));
	docv[docn].ofs = txt.len;
	docv[docn].idx = txt.len;
	doci = docn++;
}

void doc_add(const char *buf, size_t n) {
	txt_grow(n);
	memcpy(&txt.buf[txt.len], buf, n);
	txt.len += n;
	docv[doci].len += n;
}

void doc_adds(const char *s) {
	doc_add(s, strlen(s));
}

void doc_prev(void) {
	if (doci > 0) doci--;
}

void doc_next(void) {
	if (doci < docn) doci++;
}

void doc_back_line(void) {
	if (doci >= docn) return;
	struct doc *d = &docv[doci];
	size_t i = d->idx;
	while (i > 0 && txt.buf[d->idx] != '\n') i--;
	if (i > 0) i--;
	while (i > 0 && txt.buf[d->idx] != '\n') i--;
	if (i > 0) i++;
	d->idx = i;
}

void doc_print_line(void) {
	if (doci >= docn) return;
	struct doc *d = &docv[doci];
	size_t i = d->idx;
	size_t n = d->ofs + d->len;
	while (i < n && txt.buf[d->idx] != '\n') {
		putchar(txt.buf[i++]);
	}
	if (i < n) i++;
	d->idx = i;
}

void doc_init(void) {
	txt_init();
	doc_new();
	doc_adds("Type ? for command help.\n");
}

void doc_fini(void) {
	txt_fini();
}