#include <stdint.h>
#include <stddef.h>

#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/mman.h>

#include "wrmr.h"
#include "dynarr.h"
#include "txt.h"
#include "utf8.h"

void txt_replace_piece(Txt *b, u32 pi, TxtBufIdx buf, u32 ofs, u32 n) { 
	b->ptbl.v[pi] = (TxtPiece) { buf, ofs, n };
}

void txt_insert_piece(Txt *b, u32 pi, TxtBufIdx buf, u32 ofs, u32 n) { 
	DA_FIT(&b->ptbl, b->ptbl.n + 1);
	if (pi < b->ptbl.n) {
		MOVE(&b->ptbl.v[pi+1], &b->ptbl.v[pi], b->ptbl.n - pi);
	}
	txt_replace_piece(b, pi, buf, ofs, n);
	b->ptbl.n++;
}

void txt_remove_piece(Txt *b, u32 pi) {
	if (pi + 1 < b->ptbl.n) {
		MOVE(&b->ptbl.v[pi], &b->ptbl.v[pi+1], b->ptbl.n - (pi + 1));
	}
	b->ptbl.n--;
}

u32 txt_split_piece(Txt *b, u32 pi, u32 i) {
	TxtPiece *p = &b->ptbl.v[pi];
	if (i == 0) return pi;
	if (i == p->n) return pi + 1;
	txt_insert_piece(b, pi + 1, p->buf, p->ofs + i, p->n - i);
	b->ptbl.v[pi].n = i;
	return pi + 1;
}

static void txt_buf_fit(Txt *b, TxtBufIdx bi, u32 sz) {
	TxtBuf *buf = &b->buf[bi];
	if (sz > buf->c) {
		buf->c = stdc_bit_ceil(sz);
		buf->s = realloc(buf->s, buf->c);
		if (!buf->s) FAIL_WITH_MSG("realloc failure");
	}
}

static void txt_buf_append(Txt *b, TxtBufIdx bi, const char *s, u32 n) {
	TxtBuf *buf = &b->buf[bi];
	txt_buf_fit(b, bi, buf->n + n);
	memcpy(&buf->s[buf->n], s, n);
	buf->n += n;
}

TxtLoc txt_add_piece(Txt *b, TxtLoc l) {
	if (l.p > 0 && !l.i) {
		l.p--;
		l.i = b->ptbl.v[l.p].n;
	}
	if (l.p < b->ptbl.n) {
		TxtPiece *p = &b->ptbl.v[l.p];
		int mid = p->ofs + l.i < b->buf[p->buf].n;
		if (p->buf == TXT_SRC || mid) {
			l.p = txt_split_piece(b, l.p, l.i);
			goto insert;
		}
	} else {
insert:
		if (l.p < b->ptbl.n && b->ptbl.v[l.p].n == 0) {
			txt_replace_piece(b, l.p, TXT_ADD, b->buf[TXT_ADD].n, 0);
		} else {
			txt_insert_piece(b, l.p, TXT_ADD, b->buf[TXT_ADD].n, 0);
		}
	}
	return l;
}

TxtLoc txt_insert(TxtLoc l, const char *s, u32 n) {
	l = txt_add_piece(l.t, l);
	TxtPiece *p = &l.t->ptbl.v[l.p];
	txt_buf_append(l.t, p->buf, s, n);
	p->n += n;
	l.t->len += n;
	l.i = p->n;
	return l;
}

TxtLoc txt_insert_c(TxtLoc l, u32 ch) {
	char buf[6];
	u32 n = utf8_encode_len(&ch, 1);
	utf8_encode(buf, &ch, 1);
	return txt_insert(l, buf, n);
}

static int txt_are_pieces_adjacent(Txt *t, u32 a, u32 b) {
	TxtPiece *pa = &t->ptbl.v[a];
	TxtPiece *pb = &t->ptbl.v[b];
	return pa->buf == pb->buf && pa->ofs + pa->n == pb->ofs;
}

static TxtLoc txt_join_or_kill(TxtLoc l) {
	Txt *b = l.t;
	if (l.t->ptbl.v[l.p].n == 0 && !(l.p == 0 && b->ptbl.n == 1)) {
		txt_remove_piece(b, l.p);
	}
	if (l.p + 1 < b->ptbl.n && txt_are_pieces_adjacent(b, l.p, l.p + 1)) {
		b->ptbl.v[l.p].n += b->ptbl.v[l.p+1].n;
		txt_remove_piece(b, l.p + 1);
	}
	return l;
}

TxtLoc txt_delete(TxtLoc l, u32 n) {
	u32 pi = txt_split_piece(l.t, l.p, l.i);
	if (pi > 0) pi--;
	l.p = pi;
	l.i = l.t->ptbl.v[l.p].n;
	for (;;) {
		ASSERT(l.i == l.t->ptbl.v[l.p].n);
		if (l.i >= n) {
			l.i -= n;
			l.t->ptbl.v[l.p].n -= n;
			break;
		} else {
			l.t->ptbl.v[l.p].n -= l.i;
			n -= l.i;
			l.i = 0;
			if (l.p == 0) break;
			l.p = l.p - 1;
			l.i = l.t->ptbl.v[l.p].n;
		}
	}
	return txt_join_or_kill(l);
}

TxtLoc txt_delete_c(TxtLoc l) {
	while (!at_start(l) && (txt_byte(l) & 0xc0) == 0x80) 
		l = txt_delete(l, 1);
	l = txt_delete(l, 1);
	return l;
}

int txt_load(Txt *b, const char *path) {
	struct stat sb;
	int fd = open(path, O_RDONLY);
	if (fd == -1) goto empty_file;
	if (fstat(fd, &sb)) {
		close(fd);
		return -1;
	}
	if (!sb.st_size) {
empty_file:
		txt_buf_fit(b, TXT_SRC, 8192);
		goto done;
	}
	void *m = mmap(0, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
	if (m == MAP_FAILED) {
		close(fd);
		return -1;
	}
	txt_buf_fit(b, TXT_SRC, sb.st_size);
	memcpy(b->buf[TXT_SRC].s, m, sb.st_size);
	munmap(m, sb.st_size);
	b->buf[TXT_SRC].n = sb.st_size;
	close(fd);
done:
	b->ptbl.n = 0;
	b->buf[TXT_ADD].n = 0;
	b->len = b->buf[TXT_SRC].n;
	txt_insert_piece(b, 0, TXT_SRC, 0, b->len);
	return 0;
}

int txt_save(Txt *t, const char *path) {
	FILE *f = fopen(path, "wb");
	if (!f) return -1;
	for (u32 i = 0; i < t->ptbl.n; i++) {
		TxtPiece *p = &t->ptbl.v[i];
		TxtBuf *b = &t->buf[p->buf];
		fwrite(b->s + p->ofs, 1, p->n, f);
	}
	int e = ferror(f);
	fclose(f);
	return e ? -1 : 0;
}

void txt_free(Txt *t) {
	for (u32 i = 0; i < COUNTOF(t->buf); i++) {
		free(t->buf[i].s);
	}
	free(t->ptbl.v);
}

/* navigation */

TxtLoc txt_at(Txt *b, u32 ofs) {
	for (u32 i = 0; i < b->ptbl.n; i++) {
		if (ofs < b->ptbl.v[i].n) {
			return (TxtLoc) { b, i, ofs };
		}
		ofs -= b->ptbl.v[i].n;
	}
	return (TxtLoc) { b, b->ptbl.n - 1, b->ptbl.v[b->ptbl.n - 1].n };
}

u32 txt_ofs(TxtLoc l) {
	u32 r = 0;
	for (u32 i = 0; i < l.p; i++) {
		r += l.t->ptbl.v[i].n;
	}
	return r + l.i;
}

int txt_before(TxtLoc a, TxtLoc b) {
	return a.p < b.p || (a.p == b.p && a.i < b.i);
}

int txt_after(TxtLoc a, TxtLoc b) {
	return a.p > b.p || (a.p == b.p && a.i > b.i);
}

TxtLoc bnext(TxtLoc l) {
	TxtPiece *p = &l.t->ptbl.v[l.p];
	if (l.p + 1 < l.t->ptbl.n) {
		if (l.i + 1 < p->n) l.i++;
		else l.p++, l.i = 0;
	} else {
		l.i++;
		if (l.i > p->n) l.i = p->n;
	}
	return l;
}

TxtLoc bprev(TxtLoc l) {
	if (l.i > 0) {
		return (TxtLoc) { l.t, l.p, l.i - 1 };
	} else if (l.p > 0 && l.t->ptbl.v[l.p - 1].n > 0) {
		return (TxtLoc) { l.t, l.p - 1, l.t->ptbl.v[l.p - 1].n - 1 };
	} else {
		return (TxtLoc) { l.t, 0, 0 };
	}
}

TxtLoc cnext(TxtLoc l) {
	l = bnext(l);
	while ((txt_byte(l) & 0xc0) == 0x80) l = bnext(l);
	return l;
}

TxtLoc cprev(TxtLoc l) {
	l = bprev(l);
	while ((txt_byte(l) & 0xc0) == 0x80) l = bprev(l);
	return l;
}

int at_start(TxtLoc l) {
	return l.p == 0 && l.i == 0;
}

int at_end(TxtLoc l) {
	return l.p + 1 == l.t->ptbl.n && l.i == l.t->ptbl.v[l.p].n;
}

TxtLoc next_newline(TxtLoc l) {
	do l = cnext(l);
	while (!at_end(l) && txt_byte(l) != '\n');
	return l;
}

TxtLoc prev_newline(TxtLoc l) {
	do l = cprev(l);
	while (!at_start(l) && txt_byte(l) != '\n');
	return l;
}

TxtLoc start_of_line(TxtLoc l) {
	l = prev_newline(l);
	if (!at_start(l) && txt_byte(l) == '\n') l = cnext(l);
	return l;
}

TxtLoc end_of_line(TxtLoc l) {
	TxtLoc start = start_of_line(l);
	return txt_byte(start) == '\n' ? start : next_newline(start);
}

u32 get_col(TxtLoc l) {
	u32 n = 0;
	for (TxtLoc tmp = start_of_line(l); txt_before(tmp, l); txt_chr_next(&tmp)) n++;
	return n;
}

TxtLoc at_col(TxtLoc l, u32 col) {
	l = start_of_line(l);
	while (col--) {
		if (txt_chr_next(&l) == '\n') {
			l = bprev(l);
			break;
		}
	}
	return l;
}

TxtLoc prev_line(TxtLoc l) {
	TxtLoc start = start_of_line(l);
	return at_col(cprev(start), get_col(l));
}

TxtLoc next_line(TxtLoc l) {
	TxtLoc end = end_of_line(l);
	if (at_end(end)) return end;
	return at_col(cnext(end), get_col(l));
}

/* reading chars */

u32 txt_chr(TxtLoc l) {
	TxtPiece *p = &l.t->ptbl.v[l.p];
	TxtBuf *b = &l.t->buf[p->buf];
	return utf8_decode_at(b->s, p->ofs + l.i, p->ofs + p->n);
}

u8 txt_byte(TxtLoc l) {
	TxtPiece *p = &l.t->ptbl.v[l.p];
	TxtBuf *b = &l.t->buf[p->buf];
	if (l.i >= p->n) return 0;
	return b->s[p->ofs + l.i];
}

u32 txt_chr_next(TxtLoc *l) {
	if (at_end(*l)) return 0;
	u32 c = txt_chr(*l);
	u32 n = UTF8_CP_LEN(c);
	for (u32 i = 0; i < n; i++) *l = bnext(*l);
	return c;
}