/* Copyright (C) 2020  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <assert.h>
#include <err.h>
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <time.h>

#include "archive.h"

static int htmlAddress(FILE *file, const char *class, struct Address addr) {
	const char *template;
	if (addr.host) {
		template = TEMPLATE(
			<li><address class="[class]">[name]</address></li>
		);
	} else if (addr.mailbox) {
		template = TEMPLATE(
			<li class="group">
				<address class="[class]">[mailbox]</address>
				<ul>
		);
	} else {
		template = TEMPLATE(
				</ul>
			</li>
		);
	}
	struct Variable vars[] = {
		{ "class", class },
		{ "name", addressName(addr) },
		{ "mailbox", addr.mailbox },
		{0},
	};
	return templateRender(file, template, vars, escapeXML);
}

static int
htmlAddressList(FILE *file, const char *class, struct AddressList list) {
	if (!list.len) return 0;
	const char *template = TEMPLATE(
		<ul class="recipient [class]">
	);
	struct Variable vars[] = {
		{ "class", class },
		{0},
	};
	int error = templateRender(file, template, vars, escapeXML);
	if (error) return error;
	for (size_t i = 0; i < list.len; ++i) {
		error = htmlAddress(file, class, list.addrs[i]);
		if (error) return error;
	}
	return templateRender(file, TEMPLATE(</ul>), NULL, NULL);
}

static char *htmlReply(const struct Envelope *envelope) {
	const char *template = {
		"mailto:[mailbox]@[host]"
		"?cc=[cc]"
		"&subject=[re][subject]"
		"&In-Reply-To=[<][messageID][>]"
	};
	struct Variable vars[] = {
		{ "mailbox", envelope->replyTo.mailbox },
		{ "host", envelope->replyTo.host },
		{ "cc", baseMailto },
		{ "re", (strncmp(envelope->subject, "Re: ", 4) ? "Re: " : "") },
		{ "subject", envelope->subject },
		{ "messageID", envelope->messageID },
		{ "<", "<" },
		{ ">", ">" },
		{0},
	};
	return templateURL(template, vars);
}

static char *htmlFragment(const char *messageID) {
	struct Variable vars[] = {
		{ "messageID", messageID },
		{0},
	};
	return templateURL("#[messageID]", vars);
}

static char *htmlMbox(const char *messageID) {
	struct Variable vars[] = {
		{ "messageID", messageID },
		{ "type", "mbox" },
		{0},
	};
	return templateURL("../" PATH_MESSAGE, vars);
}

static int
htmlNavItem(FILE *file, const char *name, const char *base, const char *url) {
	const char *template = TEMPLATE(
		<li><a href="[base][url]">[name]</a></li>
	);
	struct Variable vars[] = {
		{ "name", name },
		{ "base", base },
		{ "url", url },
		{0},
	};
	return templateRender(file, template, vars, escapeXML);
}

int htmlMessageNav(FILE *file, const struct Envelope *envelope) {
	int error = templateRender(file, TEMPLATE(<nav><ul>), NULL, NULL);
	if (error) return error;
	if (envelope->inReplyTo) {
		char *fragment = htmlFragment(envelope->inReplyTo);
		error = htmlNavItem(file, "parent", "", fragment);
		free(fragment);
		if (error) return error;
	}
	char *mbox = htmlMbox(envelope->messageID);
	error = htmlNavItem(file, "download", "", mbox);
	free(mbox);
	if (error) return error;
	return templateRender(file, TEMPLATE(</ul></nav>), NULL, NULL);
}

static const char *htmlUTC(time_t time) {
	static char buf[sizeof("0000-00-00T00:00:00Z")];
	strftime(buf, sizeof(buf), "%FT%TZ", gmtime(&time));
	return buf;
}

int htmlMessageOpen(FILE *file, const struct Envelope *envelope) {
	const char *template = TEMPLATE(
		<article class="message" id="[messageID]">
		<header>
			<h2 class="subject"><a href="[fragment]">[subject]</a></h2>
			<address class="from">
				<a href="[reply]">[from]</a>
			</address>
			<time datetime="[utc]">[date]</time>
	);
	char *fragment = htmlFragment(envelope->messageID);
	char *reply = htmlReply(envelope);
	struct Variable vars[] = {
		{ "messageID", envelope->messageID },
		{ "fragment", fragment },
		{ "subject", envelope->subject },
		{ "reply", reply },
		{ "from", addressName(envelope->from) },
		{ "utc", htmlUTC(envelope->time) },
		{ "date", envelope->date },
		{0},
	};
	int error = 0
		|| templateRender(file, template, vars, escapeXML)
		|| htmlAddressList(file, "to", envelope->to)
		|| htmlAddressList(file, "cc", envelope->cc)
		|| htmlMessageNav(file, envelope)
		|| templateRender(file, TEMPLATE(</header>), NULL, NULL);
	free(reply);
	free(fragment);
	return error;
}

static int htmlInlineAttrs(FILE *file, const struct BodyPart *part) {
	const char *template = " " TEMPLATE([attr]="[value]");
	if (part->contentID) {
		struct Variable vars[] = {
			{ "attr", "id" },
			{ "value", part->contentID },
			{0},
		};
		int error = templateRender(file, template, vars, escapeXML);
		if (error) return error;
	}
	if (part->description) {
		struct Variable vars[] = {
			{ "attr", "title" },
			{ "value", part->description },
			{0},
		};
		int error = templateRender(file, template, vars, escapeXML);
		if (error) return error;
	}
	const char *language = NULL;
	if (part->language.type == String) language = part->language.string;
	if (part->language.type == List && part->language.list.len == 1) {
		language = dataCheck(part->language.list.ptr[0], String).string;
	}
	if (language) {
		struct Variable vars[] = {
			{ "attr", "lang" },
			{ "value", language },
			{0},
		};
		int error = templateRender(file, template, vars, escapeXML);
		if (error) return error;
	}
	return 0;
}

static void swap(char *a, char *b) {
	char ch = *a;
	*a = *b;
	*b = ch;
}

static int htmlMarkupURLs(FILE *file, char *buf) {
	static const char *Pattern = "(^|[[:space:]<])(https?:[^[:space:]>]+)(.|$)";
	static regex_t regex;
	if (!regex.re_nsub) {
		int error = regcomp(&regex, Pattern, REG_EXTENDED);
		assert(!error);
	}

	int error;
	char *ptr;
	regmatch_t match[4];
	for (ptr = buf; !regexec(&regex, ptr, 4, match, 0); ptr += match[2].rm_eo) {
		char nul = '\0';

		swap(&ptr[match[2].rm_so], &nul);
		error = escapeXML(file, ptr);
		if (error) return error;
		swap(&ptr[match[2].rm_so], &nul);

		const char *template = TEMPLATE(<a href="[url]">[url]</a>);
		swap(&ptr[match[3].rm_so], &nul);
		struct Variable vars[] = {
			{ "url", &ptr[match[2].rm_so] },
			{0},
		};
		error = templateRender(file, template, vars, escapeXML);
		if (error) return error;
		swap(&ptr[match[3].rm_so], &nul);
	}
	return escapeXML(file, ptr);
}

static int htmlMarkupQuote(FILE *file, char *buf) {
	int error;
	size_t level = 0;
	for (char *ch = buf; *ch == '>' || *ch == ' '; level += (*ch++ == '>'));
	for (size_t i = 0; i < level; ++i) {
		error = templateRender(file, TEMPLATE(<q>), NULL, NULL);
		if (error) return error;
	}
	error = htmlMarkupURLs(file, buf);
	if (error) return error;
	for (size_t i = 0; i < level; ++i) {
		error = templateRender(file, TEMPLATE(</q>), NULL, NULL);
		if (error) return error;
	}
	return 0;
}

static int htmlMarkup(FILE *file, const char *content) {
	int error = 0;
	size_t cap = 0;
	char *buf = NULL;
	bool patch = false;
	for (const char *nl; (nl = strchr(content, '\n')); content = &nl[1]) {
		size_t len = nl - content;
		if (cap < len + 1) {
			cap = len + 1;
			buf = realloc(buf, cap);
			if (!buf) err(EX_OSERR, "realloc");
		}
		memcpy(buf, content, len);
		buf[len] = '\0';
		struct Variable vars[] = {
			{ "line", buf },
			{0},
		};

		if (!strcmp(buf, "---")) {
			patch = true;
		} else if (patch && !strcmp(buf, "-- ")) {
			patch = false;
		}

		static const char *Pattern = "^(diff|index|---|[+]{3}|@@) ";
		static regex_t regex;
		if (!regex.re_nsub) {
			error = regcomp(&regex, Pattern, REG_EXTENDED);
			assert(!error);
		}
		if (patch && !regexec(&regex, buf, 0, NULL, 0)) {
			error = templateRender(
				file, TEMPLATE(<b>[line]</b>), vars, escapeXML
			);
		} else if (patch && buf[0] == '-' && strcmp(buf, "---")) {
			error = templateRender(
				file, TEMPLATE(<del>[line]</del>), vars, escapeXML
			);
		} else if (patch && buf[0] == '+') {
			error = templateRender(
				file, TEMPLATE(<ins>[line]</ins>), vars, escapeXML
			);
		} else if (patch) {
			error = escapeXML(file, buf);
		} else if (buf[0] == '>') {
			error = htmlMarkupQuote(file, buf);
		} else {
			error = htmlMarkupURLs(file, buf);
		}
		if (error) break;

		error = templateRender(file, "\n", NULL, NULL);
		if (error) break;
	}
	free(buf);
	return error;
}

int htmlInline(FILE *file, const struct BodyPart *part, const char *content) {
	return 0
		|| templateRender(file, TEMPLATE(<pre), NULL, NULL)
		|| htmlInlineAttrs(file, part)
		|| templateRender(file, TEMPLATE(>), NULL, NULL)
		|| htmlMarkup(file, content)
		|| templateRender(file, TEMPLATE(</pre>), NULL, NULL);
}

int htmlAttachmentOpen(FILE *file) {
	return templateRender(file, TEMPLATE(<ul class="attachment">), NULL, NULL);
}

int htmlAttachment(
	FILE *file, const struct BodyPart *part, const struct Variable *path
) {
	const char *template = TEMPLATE(
		<li><a href="[url]">[name][type][/][subtype]</a></li>
	);
	char *url = templateURL("../" PATH_ATTACHMENT, path);
	const char *name = paramGet(part->disposition.params, "filename");
	if (!name) name = paramGet(part->params, "name");
	struct Variable vars[] = {
		{ "url", url },
		{ "name", (name ? name : "") },
		{ "type", (name ? "" : part->type) },
		{ "/", (name ? "" : "/") },
		{ "subtype", (name ? "" : part->subtype) },
		{0},
	};
	int error = templateRender(file, template, vars, escapeXML);
	free(url);
	return error;
}

int htmlAttachmentClose(FILE *file) {
	return templateRender(file, TEMPLATE(</ul>), NULL, NULL);
}

int htmlMessageClose(FILE *file) {
	return templateRender(file, TEMPLATE(</article>), NULL, NULL);
}

static char *htmlThreadURL(const struct Envelope *envelope, const char *type) {
	struct Variable vars[] = {
		{ "messageID", envelope->messageID },
		{ "type", type },
		{0},
	};
	return templateURL("../" PATH_THREAD, vars);
}

int htmlThreadHead(FILE *file, const struct Envelope *envelope) {
	const char *template = TEMPLATE(
		<!DOCTYPE html>
		<meta charset="utf-8">
		<meta name="generator" content="[generator]">
		<title>[subject] &middot; [title]</title>
		<link rel="alternate" type="application/atom+xml" href="[atom]">
		<link rel="alternate" type="application/mbox" href="[mbox]">
	);
	char *atom = htmlThreadURL(envelope, "atom");
	char *mbox = htmlThreadURL(envelope, "mbox");
	struct Variable vars[] = {
		{ "generator", GENERATOR_URL },
		{ "subject", envelope->subject },
		{ "title", baseTitle },
		{ "atom", atom },
		{ "mbox", mbox },
		{0},
	};
	int error = templateRender(file, template, vars, escapeXML);
	free(atom);
	free(mbox);
	return error;
}

int htmlThreadOpen(FILE *file, const struct Envelope *envelope) {
	const char *template = TEMPLATE(
		<header class="thread">
			<h1>[subject]</h1>
			<nav>
				<ul>
					<li><a href="../index.html">index</a></li>
					<li><a href="[atom]">follow</a></li>
					<li><a href="[mbox]">download</a></li>
				</ul>
			</nav>
		</header>
		<main class="thread">
	);
	char *atom = htmlThreadURL(envelope, "atom");
	char *mbox = htmlThreadURL(envelope, "mbox");
	struct Variable vars[] = {
		{ "subject", envelope->subject },
		{ "atom", atom },
		{ "mbox", mbox },
		{0},
	};
	int error = templateRender(file, template, vars, escapeXML);
	free(atom);
	free(mbox);
	return error;
}

static size_t threadCount(struct List thread) {
	size_t count = 0;
	for (size_t i = 0; i < thread.len; ++i) {
		if (thread.ptr[i].type == List) {
			count += threadCount(thread.ptr[i].list);
		} else {
			count++;
		}
	}
	return count;
}

int htmlSubthreadOpen(FILE *file, struct List thread) {
	const char *template = {
		TEMPLATE(
			<details class="subthread" open>
			<summary>
		)
		TEMPLATE (
			<data class="replies" value="[replies]">[replies] repl[ies]</data>
		)
		TEMPLATE(
			</summary>
		)
	};
	size_t count = threadCount(thread);
	char replies[32];
	snprintf(replies, sizeof(replies), "%zu", count);
	struct Variable vars[] = {
		{ "replies", replies },
		{ "ies", (count > 1 ? "ies" : "y") },
		{0},
	};
	return templateRender(file, template, vars, escapeXML);
}

int htmlSubthreadClose(FILE *file) {
	return templateRender(file, TEMPLATE(</details>), NULL, NULL);
}

static int htmlFooter(FILE *file) {
	const char *template = TEMPLATE(
		<footer>
			<small><a href="[generator]">generated</a>
			<time datetime="[time]">[time]</time></small>
		</footer>
	);
	struct Variable vars[] = {
		{ "generator", GENERATOR_URL },
		{ "time", htmlUTC(time(NULL)) },
		{0},
	};
	return templateRender(file, template, vars, escapeXML);
}

int htmlThreadClose(FILE *file) {
	return 0
		|| templateRender(file, TEMPLATE(</main>), NULL, NULL)
		|| htmlFooter(file);
}

int htmlIndexHead(FILE *file) {
	const char *template = TEMPLATE(
		<!DOCTYPE html>
		<meta charset="utf-8">
		<meta name="generator" content="[generator]">
		<title>[title]</title>
		<link rel="alternate" type="application/atom+xml" href="index.atom">
	);
	struct Variable vars[] = {
		{ "generator", GENERATOR_URL },
		{ "title", baseTitle },
		{0},
	};
	return templateRender(file, template, vars, escapeXML);
}

static int htmlIndexNav(FILE *file) {
	int error = 0
		|| templateRender(file, TEMPLATE(<nav><ul>), NULL, NULL)
		|| htmlNavItem(file, "follow", "", "index.atom");
	if (error) return error;
	if (baseSubscribe) {
		error = htmlNavItem(file, "subscribe", "", baseSubscribe);
		if (error) return error;
	}
	return 0
		|| htmlNavItem(file, "write", "mailto:", baseMailto)
		|| templateRender(file, TEMPLATE(</ul></nav>), NULL, NULL);
}

int htmlIndexOpen(FILE *file) {
	const char *head = TEMPLATE(
		<header class="index">
			<h1>[title]</h1>
	);
	struct Variable vars[] = {
		{ "title", baseTitle },
		{0},
	};
	const char *tail = TEMPLATE(
		</header>
		<main class="index">
			<ol>
	);
	return 0
		|| templateRender(file, head, vars, escapeXML)
		|| htmlIndexNav(file)
		|| templateRender(file, tail, NULL, NULL);
}

static char *htmlIndexURL(const struct Envelope *envelope) {
	struct Variable vars[] = {
		{ "messageID", envelope->messageID },
		{ "type", "html" },
		{0},
	};
	return templateURL(PATH_THREAD, vars);
}

int htmlIndexThread(
	FILE *file, const struct Envelope *envelope, struct List thread
) {
	const char *template = TEMPLATE(
		<li>
			<h2 class="subject"><a href="[url]">[subject]</a></h2>
			<address class="from">[from]</address>
			<time datetime="[utc]">[date]</time>
			<data class="replies" value="[replies]">[replies] repl[ies]</data>
		</li>
	);
	char *url = htmlIndexURL(envelope);
	size_t count = threadCount(thread) - 1;
	char replies[32];
	snprintf(replies, sizeof(replies), "%zu", count);
	struct Variable vars[] = {
		{ "url", url },
		{ "subject", envelope->subject },
		{ "from", addressName(envelope->from) },
		{ "utc", htmlUTC(envelope->time) },
		{ "date", envelope->date },
		{ "replies", replies },
		{ "ies", (count == 1 ? "y" : "ies") },
		{0},
	};
	int error = templateRender(file, template, vars, escapeXML);
	free(url);
	return error;
}

int htmlIndexClose(FILE *file) {
	return 0
		|| templateRender(file, TEMPLATE(</ol></main>), NULL, NULL)
		|| htmlFooter(file);
}