/* Copyright (C) 2018  June McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <stdlib.h>
#include <sysexits.h>
#include <wchar.h>

#include "edi.h"

static struct Table alloc(size_t cap) {
	struct Slice *slices = malloc(sizeof(*slices) * cap);
	if (!slices) err(EX_OSERR, "malloc");
	return (struct Table) { 0, 0, slices };
}

struct Table tableInsert(struct Table prev, size_t at, struct Slice ins) {
	if (!prev.len) {
		struct Table next = alloc(1);
		next.slices[next.hot = next.len++] = ins;
		return next;
	}

	struct Table next = alloc(prev.len + 2);
	struct Span span = { 0, 0 };
	for (size_t i = 0; i < prev.len; ++i) {
		span = spanNext(span, prev.slices[i].len);
		if (span.at == at) {
			next.slices[next.hot = next.len++] = ins;
			next.slices[next.len++] = prev.slices[i];
		} else if (span.at < at && span.to > at) {
			next.slices[next.len++] = (struct Slice) {
				prev.slices[i].ptr,
				at - span.at,
			};
			next.slices[next.hot = next.len++] = ins;
			next.slices[next.len++] = (struct Slice) {
				&prev.slices[i].ptr[at - span.at],
				prev.slices[i].len - (at - span.at),
			};
		} else {
			next.slices[next.len++] = prev.slices[i];
		}
	}
	if (span.to == at) {
		next.slices[next.hot = next.len++] = ins;
	}
	return next;
}

struct Table tableDelete(struct Table prev, struct Span del) {
	if (!prev.len) return TableEmpty;
	struct Table next = alloc(prev.len + 1);
	struct Span span = { 0, 0 };
	for (size_t i = 0; i < prev.len; ++i) {
		span = spanNext(span, prev.slices[i].len);
		if (span.at >= del.at && span.to <= del.to) {
			(void)prev.slices[i];
			next.hot = next.len;
		} else if (span.at < del.at && span.to > del.to) {
			next.slices[next.len++] = (struct Slice) {
				prev.slices[i].ptr,
				del.at - span.at,
			};
			next.slices[next.hot = next.len++] = (struct Slice) {
				&prev.slices[i].ptr[del.to - span.at],
				prev.slices[i].len - (del.to - span.at),
			};
		} else if (span.at < del.at && span.to > del.at) {
			next.slices[next.len++] = (struct Slice) {
				prev.slices[i].ptr,
				del.at - span.at,
			};
			next.hot = next.len;
		} else if (span.at < del.to && span.to > del.to) {
			next.slices[next.hot = next.len++] = (struct Slice) {
				&prev.slices[i].ptr[del.to - span.at],
				prev.slices[i].len - (del.to - span.at),
			};
		} else {
			next.slices[next.len++] = prev.slices[i];
		}
	}
	return next;
}

#ifdef TEST
#include <assert.h>

static struct Slice slice(const wchar_t *str) {
	return (struct Slice) { str, wcslen(str) };
}

static struct Span span(size_t at, size_t to) {
	return (struct Span) { at, to };
}

static int eq(const wchar_t *str, struct Table table) {
	for (size_t i = 0; i < table.len; ++i) {
		if (wcsncmp(str, table.slices[i].ptr, table.slices[i].len)) {
			return 0;
		}
		str = &str[table.slices[i].len];
	}
	return !str[0];
}

static int hot(wint_t ch, struct Table table) {
	if (table.hot == table.len) {
		return ch == WEOF;
	} else {
		return ch == table.slices[table.hot].ptr[0];
	}
}

int main() {
	struct Table abc = tableInsert(TableEmpty, 0, slice(L"ABC"));
	assert(eq(L"ABC", abc));
	assert(hot(L'A', abc));

	struct Table dabc = tableInsert(abc, 0, slice(L"D"));
	struct Table abcd = tableInsert(abc, 3, slice(L"D"));
	struct Table adbc = tableInsert(abc, 1, slice(L"D"));

	assert(eq(L"DABC", dabc));
	assert(eq(L"ABCD", abcd));
	assert(eq(L"ADBC", adbc));

	assert(hot(L'D', dabc));
	assert(hot(L'D', abcd));
	assert(hot(L'D', adbc));

	free(dabc.slices);
	free(abcd.slices);
	free(adbc.slices);

	struct Table bc = tableDelete(abc, span(0, 1));
	struct Table ab = tableDelete(abc, span(2, 3));
	struct Table ac = tableDelete(abc, span(1, 2));
	struct Table __ = tableDelete(abc, span(0, 3));

	assert(eq(L"BC", bc));
	assert(eq(L"AB", ab));
	assert(eq(L"AC", ac));
	assert(eq(L"",   __));

	assert(hot(L'B', bc));
	assert(hot(WEOF, ab));
	assert(hot(L'C', ac));
	assert(hot(WEOF, __));

	free(bc.slices);
	free(ab.slices);
	free(ac.slices);
	free(__.slices);

	free(abc.slices);
}

#endif