/* 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 <err.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>
				<address class="[class] group">[mailbox]</address>
				<ul class="group">
		);
	} 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 *htmlMailto(const struct Envelope *envelope) {
	const char *template = {
		"mailto:[mailbox]@[host]?subject=[re][subject]&In-Reply-To=[messageID]"
	};
	struct Variable vars[] = {
		{ "mailbox", envelope->from.mailbox },
		{ "host", envelope->from.host },
		{ "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);
}

int htmlMessageNav(FILE *file, const struct Envelope *envelope) {
	int error = templateRender(file, TEMPLATE(<nav><ul>), NULL, NULL);
	if (error) return error;
	if (envelope->inReplyTo) {
		const char *template = TEMPLATE(
			<li><a href="[fragment]">parent</a></li>
		);
		char *fragment = htmlFragment(envelope->inReplyTo);
		struct Variable vars[] = {
			{ "fragment", fragment },
			{0},
		};
		error = templateRender(file, template, vars, escapeXML);
		free(fragment);
		if (error) return error;
	}
	const char *template = TEMPLATE(
		<li><a href="[mbox]">download</a></li>
	);
	char *mbox = htmlMbox(envelope->messageID);
	struct Variable vars[] = {
		{ "mbox", mbox },
		{0},
	};
	error = templateRender(file, template, vars, escapeXML);
	free(mbox);
	if (error) return error;
	return templateRender(file, TEMPLATE(</ul></nav>), NULL, NULL);
}

int htmlMessageOpen(FILE *file, const struct Envelope *envelope) {
	// TODO: Conditionally include mailto: link.
	const char *template = TEMPLATE(
		<article class="message" id="[messageID]">
		<header>
			<h2 class="subject"><a href="[fragment]">[subject]</a></h2>
			<address class="from">
				<a href="[mailto]">[from]</a>
			</address>
			<time datetime="[utc]">[date]</time>
	);
	char *fragment = htmlFragment(envelope->messageID);
	char *mailto = htmlMailto(envelope);
	char utc[sizeof("0000-00-00T00:00:00Z")];
	strftime(utc, sizeof(utc), "%FT%TZ", gmtime(&envelope->time));
	struct Variable vars[] = {
		{ "messageID", envelope->messageID },
		{ "fragment", fragment },
		{ "subject", envelope->subject },
		{ "mailto", mailto },
		{ "from", addressName(envelope->from) },
		{ "utc", utc },
		{ "date", envelope->date },
		{0},
	};
	int error = 0
		|| templateRender(file, template, vars, escapeXML)
		|| htmlMessageNav(file, envelope)
		|| htmlAddressList(file, "to", envelope->to)
		|| htmlAddressList(file, "cc", envelope->cc)
		|| templateRender(file, TEMPLATE(</header>), NULL, NULL);
	free(mailto);
	free(fragment);
	return error;
}

static int htmlInlineAttrs(FILE *file, const struct BodyPart *part) {
	const char *template = " [attr]=\"[value]\"";
	if (part->id) {
		struct Variable vars[] = {
			{ "attr", "id" },
			{ "value", part->id },
			{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 bool isPatch(const char *content) {
	return !strncmp(content, "---\n", 4) || strstr(content, "\n---\n");
}

static int htmlPatch(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[1] - 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, "---\n")) {
			patch = true;
		} else if (patch && !strcmp(buf, "-- \n")) {
			patch = false;
		}

		if (patch && !strncmp(buf, "@@", 2)) {
			error = templateRender(
				file, TEMPLATE(<b>[line]</b>), vars, escapeXML
			);
		} else if (patch && buf[0] == '-' && strncmp(buf, "---", 3)) {
			error = templateRender(
				file, TEMPLATE(<del>[line]</del>), vars, escapeXML
			);
		} else if (patch && buf[0] == '+' && strncmp(buf, "+++", 3)) {
			error = templateRender(
				file, TEMPLATE(<ins>[line]</ins>), vars, escapeXML
			);
		} else {
			error = escapeXML(file, buf);
		}
		if (error) break;
	}
	free(buf);
	return error;
}

int htmlInline(FILE *file, const struct BodyPart *part, const char *content) {
	int error = 0
		|| templateRender(file, TEMPLATE(<pre), NULL, NULL)
		|| htmlInlineAttrs(file, part)
		|| templateRender(file, TEMPLATE(>), NULL, NULL);
	if (error) return error;
	if (isPatch(content)) {
		error = htmlPatch(file, content);
	} else {
		error = escapeXML(file, content);
	}
	return error || 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");
	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);
}

const char *htmlTitle;

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">
		<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[] = {
		{ "subject", envelope->subject },
		{ "title", htmlTitle },
		{ "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="[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>[replies] repl[ies]</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);
}

int htmlThreadClose(FILE *file) {
	const char *template = TEMPLATE(
		</main>
		<footer>
			generated <time datetime="[time]">[time]</time>
		</footer>
	);
	time_t now = time(NULL);
	char time[sizeof("0000-00-00T00:00:00Z")];
	strftime(time, sizeof(time), "%FT%TZ", gmtime(&now));
	struct Variable vars[] = {
		{ "time", time },
		{0},
	};
	return templateRender(file, template, vars, escapeXML);
}