import type { Hono } from "hono";
import { isSafePath } from "../bucket/repo.ts";
import { describeFile } from "../describe/describe.ts";
import {
	fileAt,
	filesAt,
	headId,
	history,
	objectBytes,
	repoStats,
	type Save,
	saveByPrefix,
	timeline,
} from "../mirror/queries.ts";
import { mirrorState } from "../mirror/store.ts";
import { visibleReleases } from "../releases/releases.ts";
import { setting } from "../server/db.ts";
import { atlasPanel, atlasPickerRows, atlasSection } from "./atlas.ts";
import { type Html, html } from "./html.ts";
import {
	cacheFor,
	notFound,
	openPublicRepo,
	type PageContext,
	type PublicRepo,
	page,
	plural,
	relativeTime,
} from "./layout.ts";
import { renderMarkdown, renderParagraph } from "./markdown.ts";
import { timelineSaves, timelineSvg } from "./timeline.ts";

const PAGE_SIZE = 50;
// Each opens inline under the tabs (kepr.js), as Kepr 2's panels did; the page is the fallback.
const PANELS = [
	["issues", "issues"],
	["builds", "releases"],
	["archives", "archives"],
];
const HTTP_URL = /^https?:\/\//i;

export function registerRepoPage(app: Hono, ctx: PageContext): void {
	app.get("/:repo", (c) => {
		const repo = openPublicRepo(ctx, c.req.param("repo"));
		if (!repo) return notFound(c, ctx);
		// `?at=<id>` shows the Atlas at that save (§21.5); the rest of the page stays at HEAD.
		const at = c.req.query("at");
		const atSave = at === undefined ? null : saveByPrefix(repo.mirror, at);
		if (at !== undefined && !atSave) return notFound(c, ctx);
		const pageNumber = Math.max(1, Number.parseInt(c.req.query("page") ?? "1", 10) || 1);
		const name = repo.settings.name;
		const intro = repoIntro(repo);
		cacheFor(c, false);
		return c.html(
			page(ctx, {
				title: name,
				description: intro?.text ?? "",
				path: `/${name}`,
				body: html`${header(ctx, repo, intro?.html ?? null)}
${headId(repo.mirror) && sections(repo, pageNumber, atSave?.id ?? null)}
${details(repoDetails(repo))}`,
			}),
		);
	});
	// The timeline's saves, fetched by kepr.js once the page has drawn (§21.4).
	app.get("/:repo/timeline", (c) => {
		const repo = openPublicRepo(ctx, c.req.param("repo"));
		if (!repo) return notFound(c, ctx);
		cacheFor(c, false);
		return c.json(timelineSaves(timeline(repo.mirror)));
	});
	// The Atlas picker's rows, fetched by kepr.js when it first opens (§21.5).
	app.get("/:repo/atlas/saves", (c) => {
		const repo = openPublicRepo(ctx, c.req.param("repo"));
		const at = c.req.query("at");
		const save = repo && at !== undefined ? saveByPrefix(repo.mirror, at) : null;
		if (!repo || (at !== undefined && !save)) return notFound(c, ctx);
		cacheFor(c, false);
		const rows = atlasPickerRows(repo.settings.name, timeline(repo.mirror), save?.id ?? null);
		return c.html(rows.map(String).join(""));
	});
	// One Atlas row's detail panel, fetched by kepr.js on hover or select (§21.5).
	app.get("/:repo/atlas/panel", (c) => {
		const repo = openPublicRepo(ctx, c.req.param("repo"));
		const at = c.req.query("at");
		const path = c.req.query("path") ?? "";
		const save = repo && (at === undefined ? null : saveByPrefix(repo.mirror, at));
		const saveId = save?.id ?? (repo && headId(repo.mirror));
		const panel =
			repo &&
			saveId &&
			(at === undefined || save) &&
			isSafePath(path.replace(/\/$/, "")) &&
			atlasPanel(repo, saveId, save?.id ?? null, path);
		if (!panel) return notFound(c, ctx);
		cacheFor(c, save !== null && save !== undefined);
		return c.html(String(panel));
	});
}

/**
 * The repo's description, as markup and as plain text: the operator's own, or else the README's
 * first paragraph (§21.4).
 */
export function repoIntro(repo: PublicRepo): { html: Html; text: string } | null {
	const { name, description } = repo.settings;
	if (description)
		return renderParagraph(description, { repo: name, dir: "", at: null, own: true });
	const readme = readmeAtHead(repo.mirror);
	const paragraph = readme === null ? null : describeFile("README.md", readme);
	return paragraph === null ? null : renderParagraph(paragraph, { repo: name, dir: "", at: null });
}

/** The details section: the operator's own Markdown, or else the rendered README. */
export function repoDetails(repo: PublicRepo): Html | null {
	const { name, details } = repo.settings;
	if (details) return renderMarkdown(details, { repo: name, dir: "", at: null, own: true });
	const readme = readmeAtHead(repo.mirror);
	return readme === null ? null : renderMarkdown(readme, { repo: name, dir: "", at: null });
}

export function readmeAtHead(mirror: PublicRepo["mirror"]): string | null {
	const head = headId(mirror);
	const path =
		head && filesAt(mirror, head).find((f) => f.path.toLowerCase() === "readme.md")?.path;
	const file = head && path ? fileAt(mirror, head, path) : null;
	const bytes = file && objectBytes(mirror, file.hash);
	return bytes ? new TextDecoder().decode(bytes) : null;
}

function header(ctx: PageContext, repo: PublicRepo, intro: Html | null): Html {
	const { name, homepage, languages } = repo.settings;
	const steal = `koh steal ${ctx.domain}/${name}`;
	const stats = repoStats(repo.mirror);
	const handle = setting(ctx.kepr, "handle");
	// §21.4: the version is the newest release; with none, the version the project declares, by
	// Koh's rule, at its newest save.
	const version =
		visibleReleases(ctx.kepr, repo.mirror, name)[0]?.version ||
		mirrorState(repo.mirror, "declared_version");
	const meta = [
		version && `v${version}`,
		plural(stats.saves, "save"),
		stats.lines > 0 && plural(stats.lines, "line"),
		stats.updated !== null && `updated ${relativeTime(stats.updated)}`,
	].filter(Boolean);
	return html`<header class="repo-head">
<h1 class="repo-name">${name}</h1>
${handle && html`<p class="repo-contributor mono"><a href="/@${handle}">@${handle}</a></p>`}
${html`<div class="repo-desc"${!intro && " hidden"}><p>${intro}</p></div>`}
${
	HTTP_URL.test(homepage) &&
	html`<p class="repo-homepage"><a href="${homepage}">${homepage}</a></p>`
}
${
	(languages.length > 0 || stats.language) &&
	html`<div class="lang-badges">${(languages.length > 0 ? languages : [stats.language]).map(
		(language) => html`<span class="lang-badge">${language}</span>`,
	)}</div>`
}
<p class="repo-meta">${meta.join(" · ")}</p>
<div class="repo-tabbar">
<nav class="repo-tabs" aria-label="Repository panels">${PANELS.map(
		([label, path]) =>
			html`<a class="repo-tab" href="/${name}/${path}" data-panel="${path}">${label}</a>`,
	)}</nav>
<div class="install-lines">
<button type="button" class="repo-steal-btn" data-copy="${steal}">${steal}</button>
</div>
</div>
<div class="repo-panel" hidden></div>
</header>`;
}

function sections(repo: PublicRepo, requestedPage: number, at: string | null): Html {
	const name = repo.settings.name;
	const saves = timeline(repo.mirror);
	// Past the last page, even at an unbindable number like Infinity, is page 1.
	const pageNumber = (requestedPage - 1) * PAGE_SIZE < saves.length ? requestedPage : 1;
	const rows = history(repo.mirror, PAGE_SIZE, (pageNumber - 1) * PAGE_SIZE);
	const pages: Pages = {
		at,
		newer: pageNumber > 1 ? pageNumber - 1 : null,
		older: pageNumber * PAGE_SIZE < saves.length ? pageNumber + 1 : null,
	};
	const atlas = atlasSection(repo, at ?? (headId(repo.mirror) as string), at);
	return html`<section class="repo-section">
<details class="repo-section-toggle" open>
<summary class="section-head"><span class="section-label">timeline</span></summary>
${timelineSvg(name, saves)}
</details>
</section>
${atlas}
<section class="repo-section" id="history">
<details class="repo-section-toggle" open>
<summary class="section-head"><span class="section-label">history</span></summary>
${saveList(name, rows, pages)}
</details>
</section>`;
}

type Pages = { at: string | null; newer: number | null; older: number | null };

/**
 * One page of saves in a box that scrolls four rows at a time, as Kepr 2's; kepr.js fetches the
 * older pages into it as it scrolls, and without JavaScript the pager links page the whole view.
 */
function saveList(repo: string, rows: Save[], pages: Pages): Html {
	const pageHref = (n: number) => {
		const query = new URLSearchParams(pages.at ? { at: pages.at } : {});
		query.set("page", String(n));
		return `?${query}#history`;
	};
	return html`<div class="save-list" data-list="history">
${rows.map(
	(save) =>
		html`<a class="history-row" href="/${repo}/saves/${save.id}"><span class="history-id">${save.id}</span><span class="history-msg">${save.message.split("\n")[0]}</span><span class="history-when">${relativeTime(save.created_at)}</span></a>`,
)}
${
	(pages.newer || pages.older) &&
	html`<p class="pager mono">${pages.newer && html`<a href="${pageHref(pages.newer)}">← newer</a>`}${pages.older && html`<a class="pager-older" href="${pageHref(pages.older)}">older →</a>`}</p>`
}
</div>`;
}

// Empty and hidden when there is nothing to show, so a signed-in editor still has a place to write.
function details(body: Html | null): Html {
	return html`<section class="repo-details"${!body && " hidden"}>
<details class="repo-details-toggle" open>
<summary class="repo-details-head">details</summary>
<div class="repo-details-body markdown">${body}</div>
</details>
</section>`;
}