<?php

declare(strict_types=1);

/**
 * Builds the public client handbook: one document containing every piece of
 * documentation and every source file of client-package/.
 *
 * Everything is read from disk on each request, so the published page always
 * matches the repository - there is no build step and nothing to regenerate
 * after an edit.
 *
 * Two renderings share this assembly:
 *   index.php  HTML, rendered client-side with the vendored marked.js
 *   llms.php   text/plain Markdown, meant to be fed to an agent verbatim
 */

const HANDBOOK_PACKAGE_DIR = __DIR__ . "/../../client-package";
const HANDBOOK_CONTENT_DIR = __DIR__ . "/../content";

/**
 * Paths inside client-package/ that must never be published.
 *
 * config.php holds the instance token. It is git-ignored and stripped by
 * build-client-package.sh, but this page is public, so it is excluded here by
 * path as well instead of relying on it being absent.
 */
const HANDBOOK_EXCLUDED = [
    "manage-client/config.php",
];

/** Vendored third-party files: listed in the inventory, never reproduced. */
const HANDBOOK_VENDORED = [
    "docs/assets/marked.min.js",
];

function handbookRepoRoot(): string
{
    return dirname(__DIR__, 2);
}

/**
 * Absolute base URL of this installation.
 *
 * Prefers the configured MANAGE_PUBLIC_URL so that copied links keep working;
 * falls back to the current request for installations served under a different
 * name (staging, a local `php -S`).
 */
function handbookBaseUrl(): string
{
    $configured = "";
    $config = handbookRepoRoot() . "/config.php";
    if (is_file($config)) {
        // Read as text: including the server config would pull in its side
        // effects, and a public page needs none of them.
        $source = (string) file_get_contents($config);
        if (preg_match('/define\(\s*"MANAGE_PUBLIC_URL"\s*,\s*"([^"]*)"/', $source, $match) === 1) {
            $configured = trim($match[1]);
        }
    }

    if ($configured !== "" && preg_match('#^https?://#i', $configured) === 1) {
        return rtrim($configured, "/");
    }

    $scheme = ($_SERVER["HTTPS"] ?? "") === "on"
        || ($_SERVER["HTTP_X_FORWARDED_PROTO"] ?? "") === "https" ? "https" : "http";
    $host = (string) ($_SERVER["HTTP_HOST"] ?? "localhost");
    // dirname(SCRIPT_NAME) ends with this directory's name; dropping that
    // suffix yields the mount point of the manage installation itself.
    $dir = rtrim(str_replace("\\", "/", dirname($_SERVER["SCRIPT_NAME"] ?? "")), "/");
    $own = "/" . handbookDirName();
    if (str_ends_with($dir, $own)) {
        $dir = substr($dir, 0, -strlen($own));
    }

    return $scheme . "://" . $host . $dir;
}

/** Name of this documentation directory, as it appears in the URL. */
function handbookDirName(): string
{
    return basename(dirname(__DIR__));
}

/**
 * Absolute URL of this documentation directory, without a trailing slash.
 *
 * Derived from the installation base rather than from the request path, so a
 * MANAGE_PUBLIC_URL that carries a subdirectory is not duplicated.
 */
function handbookSelfUrl(): string
{
    return handbookBaseUrl() . "/" . handbookDirName();
}

function handbookEscape(string $value): string
{
    return htmlspecialchars($value, ENT_QUOTES | ENT_SUBSTITUTE, "UTF-8");
}

/** Stable anchor id for a section, usable in both the nav and the document. */
function handbookAnchor(string $prefix, string $key): string
{
    $slug = strtolower($key);
    $slug = preg_replace('/[^a-z0-9]+/', "-", $slug) ?? $slug;

    return $prefix . "-" . trim($slug, "-");
}

/** Fence language for a source file, by extension. */
function handbookLanguage(string $relative): string
{
    $name = basename($relative);
    if ($name === ".htaccess") {
        return "apacheconf";
    }
    if (str_ends_with($name, ".cron")) {
        return "text";
    }

    return match (strtolower(pathinfo($relative, PATHINFO_EXTENSION))) {
        "php" => "php",
        "sh", "bash" => "bash",
        "css" => "css",
        "js" => "javascript",
        "json" => "json",
        "md" => "markdown",
        default => "text",
    };
}

/**
 * Recursively lists every file under client-package/, relative to it.
 *
 * @return string[] sorted relative paths
 */
function handbookScanPackage(): array
{
    $root = realpath(HANDBOOK_PACKAGE_DIR);
    if ($root === false || !is_dir($root)) {
        return [];
    }

    $iterator = new RecursiveIteratorIterator(
        new RecursiveDirectoryIterator($root, FilesystemIterator::SKIP_DOTS),
        RecursiveIteratorIterator::SELF_FIRST,
    );

    $files = [];
    foreach ($iterator as $item) {
        if (!$item->isFile()) {
            continue;
        }

        $relative = str_replace("\\", "/", substr($item->getPathname(), strlen($root) + 1));
        $name = basename($relative);

        // Local noise that is not part of the handed-out package.
        if ($name === ".DS_Store" || str_ends_with($name, ".log")) {
            continue;
        }
        if (in_array($relative, HANDBOOK_EXCLUDED, true)) {
            continue;
        }

        $files[] = $relative;
    }

    sort($files, SORT_STRING);

    return $files;
}

/**
 * Splits the package into the documentation chapters and the source files.
 *
 * @return array{docs: array<string, string>, code: string[], vendored: string[]}
 *         docs maps relative path -> chapter title, in reading order
 */
function handbookInventory(): array
{
    $docs = [];
    $code = [];
    $vendored = [];

    foreach (handbookScanPackage() as $relative) {
        if (in_array($relative, HANDBOOK_VENDORED, true)) {
            $vendored[] = $relative;
            continue;
        }

        if (str_ends_with($relative, ".md")) {
            $number = preg_match('#/(\d+)_#', $relative, $match) === 1 ? $match[1] . " · " : "";
            $docs[$relative] = $number . handbookChapterTitle($relative);
            continue;
        }

        $code[] = $relative;
    }

    // README first, then the numbered chapters in order.
    uksort($docs, static function (string $a, string $b): int {
        if ($a === "README.md") {
            return -1;
        }
        if ($b === "README.md") {
            return 1;
        }

        return strcmp($a, $b);
    });

    usort($code, static function (string $a, string $b): int {
        return [handbookCodeWeight($a), $a] <=> [handbookCodeWeight($b), $b];
    });

    return ["docs" => $docs, "code" => $code, "vendored" => $vendored];
}

/**
 * Reading order for the source part: the files that are copied into the host
 * project first, entry point before the modules it pulls in, examples and
 * tooling last. Anything unrecognised sorts to the end alphabetically, so a
 * newly added file still lands somewhere sensible.
 */
function handbookCodeWeight(string $relative): int
{
    return match (true) {
        $relative === "manage-client/config.sample.php" => 10,
        $relative === "manage-client/lib/client.php" => 11,
        $relative === "manage-client/lib/updater.php" => 12,
        $relative === "manage-client/lib/backup.php" => 13,
        $relative === "manage-client/lib/remote.php" => 14,
        str_starts_with($relative, "manage-client/lib/") => 15,
        str_starts_with($relative, "manage-client/bin/") => 16,
        str_starts_with($relative, "manage-client/ui/") => 17,
        str_starts_with($relative, "manage-client/") => 18,
        str_starts_with($relative, "examples/") => 20,
        str_starts_with($relative, "scripts/") => 21,
        default => 30,
    };
}

/**
 * Title of a chapter: its own first-level heading, so the handbook shows what
 * the document calls itself rather than a name derived from the file.
 */
function handbookChapterTitle(string $relative): string
{
    if (preg_match('/^#\s+(.+)$/m', handbookReadDoc($relative), $match) === 1) {
        return trim($match[1]);
    }

    return ucwords(strtolower(str_replace("_", " ", basename($relative, ".md"))));
}

function handbookReadDoc(string $relative): string
{
    $path = HANDBOOK_PACKAGE_DIR . "/" . $relative;

    return is_file($path) ? (string) file_get_contents($path) : "";
}

/** Drops the leading h1; the assembly emits it as the chapter heading instead. */
function handbookStripTitle(string $markdown): string
{
    return preg_replace('/^#\s+.+\R+/', "", ltrim($markdown), 1) ?? $markdown;
}

/** Reads an authored page from content/, with the placeholders filled in. */
function handbookContent(string $name, array $replacements = []): string
{
    $path = HANDBOOK_CONTENT_DIR . "/" . $name;
    $text = is_file($path) ? (string) file_get_contents($path) : "";

    foreach ($replacements as $key => $value) {
        $text = str_replace("{{" . $key . "}}", (string) $value, $text);
    }

    return rtrim($text) . "\n";
}

/**
 * Rewrites the relative links between the chapters so they point at the
 * anchors of this single page instead of at neighbouring .md files.
 */
function handbookRewriteLinks(string $markdown, array $docs): string
{
    $targets = [];
    foreach ($docs as $relative => $_title) {
        $targets[basename($relative)] = "#" . handbookAnchor("doc", $relative);
    }

    return preg_replace_callback(
        '/\]\(([^)\s]+\.md)(#[^)\s]*)?\)/',
        static function (array $match) use ($targets): string {
            $file = basename($match[1]);

            return isset($targets[$file]) ? "](" . $targets[$file] . ")" : $match[0];
        },
        $markdown,
    ) ?? $markdown;
}

/**
 * Demotes every heading of an embedded chapter by one level, so the assembled
 * document keeps a single h1 and the chapters sit below the part headings.
 */
function handbookDemoteHeadings(string $markdown): string
{
    $lines = explode("\n", $markdown);
    $inFence = false;

    foreach ($lines as $index => $line) {
        if (preg_match('/^\s*(```|~~~)/', $line) === 1) {
            $inFence = !$inFence;
            continue;
        }
        if (!$inFence && preg_match('/^(#{1,5})\s/', $line) === 1) {
            $lines[$index] = "#" . $line;
        }
    }

    return implode("\n", $lines);
}

/**
 * Assembles the complete handbook as one Markdown document.
 *
 * @param bool $withAnchors emit HTML anchor targets for the in-page navigation.
 *                          Off for the plain-text rendering, which has no nav.
 */
function handbookBuildMarkdown(bool $withAnchors): string
{
    $inventory = handbookInventory();
    $base = handbookBaseUrl();
    $self = handbookSelfUrl();

    $anchor = static function (string $id) use ($withAnchors): string {
        return $withAnchors ? '<a id="' . $id . '"></a>' . "\n\n" : "";
    };

    $out = [];

    $out[] = $anchor("part-intro") . handbookContent("00_UEBERBLICK.md", [
        "BASE_URL" => $base,
        "SELF_URL" => $self,
        "DOC_COUNT" => (string) count($inventory["docs"]),
        "CODE_COUNT" => (string) count($inventory["code"]),
    ]);

    // ---- Table of contents -------------------------------------------------
    $toc = ["## Inhalt", ""];
    $toc[] = "**Teil 1 – Dokumentation**";
    $toc[] = "";
    foreach ($inventory["docs"] as $relative => $title) {
        $link = $withAnchors ? "[" . $title . "](#" . handbookAnchor("doc", $relative) . ")" : $title;
        $toc[] = "- " . $link . " — `client-package/" . $relative . "`";
    }
    $toc[] = "";
    $toc[] = "**Teil 2 – HTTP-API**";
    $toc[] = "";
    $toc[] = $withAnchors ? "- [OpenAPI-Spezifikation](#part-api)" : "- OpenAPI-Spezifikation";
    $toc[] = "";
    $toc[] = "**Teil 3 – Quellcode**";
    $toc[] = "";
    foreach ($inventory["code"] as $relative) {
        $link = $withAnchors ? "[" . $relative . "](#" . handbookAnchor("code", $relative) . ")" : $relative;
        $toc[] = "- " . $link;
    }
    $out[] = implode("\n", $toc) . "\n";

    // ---- Part 1: documentation --------------------------------------------
    $out[] = $anchor("part-docs") . "# Teil 1 – Dokumentation\n";

    foreach ($inventory["docs"] as $relative => $title) {
        $body = handbookStripTitle(handbookReadDoc($relative));
        $body = handbookRewriteLinks($body, $inventory["docs"]);
        $body = handbookDemoteHeadings($body);

        $out[] = $anchor(handbookAnchor("doc", $relative))
            . "## " . $title . "\n\n"
            . "> Quelle: `client-package/" . $relative . "`\n\n"
            . rtrim($body) . "\n";
    }

    // ---- Part 2: the HTTP API ---------------------------------------------
    $spec = handbookOpenApiJson();
    $out[] = $anchor("part-api") . handbookContent("50_API.md", [
        "BASE_URL" => $base,
        "SELF_URL" => $self,
    ]) . "\n"
        . "## OpenAPI 3.1 (vollständig)\n\n"
        . "```json\n" . rtrim($spec) . "\n```\n";

    // ---- Part 3: the source ------------------------------------------------
    $out[] = $anchor("part-code") . "# Teil 3 – Quellcode\n\n"
        . "Alle " . count($inventory["code"]) . " Quelldateien des Client-Pakets, vollständig und\n"
        . "unverändert. Die Pfade sind relativ zu `client-package/`.\n\n"
        . "Die Reihenfolge folgt der Wichtigkeit für eine Einbindung: zuerst die Vorlage der\n"
        . "Konfiguration und `lib/client.php` als einziger Einstiegspunkt, dann Updater, Backup\n"
        . "und die übrigen Module, danach Kommandozeile und Oberfläche, zuletzt Beispiele und\n"
        . "Werkzeuge. Für eine Übernahme wird der Ordner `manage-client/` gebraucht; alles\n"
        . "darunter gehört dazu, `examples/`, `docs/` und `scripts/` nicht.\n";

    foreach ($inventory["code"] as $relative) {
        $path = HANDBOOK_PACKAGE_DIR . "/" . $relative;
        $body = is_file($path) ? (string) file_get_contents($path) : "";
        $fence = handbookFenceFor($body);

        $out[] = $anchor(handbookAnchor("code", $relative))
            . "## `" . $relative . "`\n\n"
            . $fence . handbookLanguage($relative) . "\n"
            . rtrim($body) . "\n" . $fence . "\n";
    }

    // ---- Inventory ---------------------------------------------------------
    $out[] = $anchor("part-inventory") . handbookInventoryTable($inventory);

    return implode("\n", $out);
}

/**
 * Picks a fence long enough to survive content that itself contains one.
 * lib/zip.php and the docs both embed triple backticks.
 */
function handbookFenceFor(string $body): string
{
    $longest = 0;
    if (preg_match_all('/^\s*(`{3,})/m', $body, $matches) > 0) {
        foreach ($matches[1] as $run) {
            $longest = max($longest, strlen($run));
        }
    }

    return str_repeat("`", max(3, $longest + 1));
}

function handbookInventoryTable(array $inventory): string
{
    $rows = ["# Dateiübersicht", "", "| Datei | Größe | Rolle |", "|---|---:|---|"];

    foreach ($inventory["docs"] as $relative => $_title) {
        $rows[] = handbookInventoryRow($relative, "Dokumentation");
    }
    foreach ($inventory["code"] as $relative) {
        $rows[] = handbookInventoryRow($relative, "Quellcode");
    }
    foreach ($inventory["vendored"] as $relative) {
        $rows[] = handbookInventoryRow($relative, "Fremdbibliothek, hier nicht abgedruckt");
    }

    return implode("\n", $rows) . "\n";
}

function handbookInventoryRow(string $relative, string $role): string
{
    $size = @filesize(HANDBOOK_PACKAGE_DIR . "/" . $relative);

    return "| `" . $relative . "` | " . ($size === false ? "–" : number_format((int) $size, 0, ",", ".") . " B")
        . " | " . $role . " |";
}

/** The OpenAPI document, with the live server URL substituted. */
function handbookOpenApiJson(): string
{
    $path = __DIR__ . "/../openapi.json";
    $raw = is_file($path) ? (string) file_get_contents($path) : "{}";

    $spec = json_decode($raw, true);
    if (!is_array($spec)) {
        return $raw;
    }

    $spec["servers"] = [[
        "url" => handbookBaseUrl() . "/api/v1",
        "description" => "Diese Manage-Installation",
    ]];

    return (string) json_encode(
        $spec,
        JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE,
    );
}