<?php

namespace app\service;

use RuntimeException;
use Symfony\Component\Uid\Ulid;

class ArticleImportService
{
    private const DEFAULT_CHUNK_SIZE = 800;
    private const DEFAULT_CHUNK_OVERLAP = 120;
    private const MIN_CHUNK_SIZE = 100;
    private const MAX_CHUNK_SIZE = 4000;
    private const SENTENCE_BOUNDARY_PATTERN = '/(?<=[。！？；.!?;])\s*|\R+/u';
    private const MARKDOWN_PAGE_PATTERN = '/<!--\s*DOCMASTER:PAGE\s+0*([0-9A-Za-z_-]+)\s*-->\s*(?:#+\s*Page\s+\S+\s*)?(.*?)(?=\n---\s*\n\s*<!--\s*DOCMASTER:PAGE|\z)/su';

    public function import(array $payload): array
    {
        $payload = $this->normalizePayload($payload);
        $payload = $this->applyMetadataFallbacks($payload);
        $errors = $this->validate($payload);
        if ($errors !== []) {
            return ['ok' => false, 'errors' => $errors];
        }

        $archiveUid = $this->archiveUid($payload);
        $archive = $this->archive($payload, $archiveUid);
        $pageBlocks = $this->pageBlocks($payload);
        $chunkSize = $this->intOption($payload, 'chunk_size', self::DEFAULT_CHUNK_SIZE);
        $chunkOverlap = $this->intOption($payload, 'chunk_overlap', self::DEFAULT_CHUNK_OVERLAP);

        $chunks = $this->chunksFromPages($archiveUid, $pageBlocks, $chunkSize, $chunkOverlap);
        $pages = $this->pagesSummary($pageBlocks, $chunks);
        $needsAiMetadata = (new ArchiveRepository())->archiveNeedsMetadata($archive);

        return [
            'ok' => true,
            'data' => [
                'import_uid' => $archiveUid,
                'archive' => $archive,
                'chunks' => $chunks,
                'pages' => $pages,
                'stats' => [
                    'page_count' => count($pages),
                    'page_block_count' => count($pageBlocks),
                    'chunk_count' => count($chunks),
                    'chunk_size' => $chunkSize,
                    'chunk_overlap' => $chunkOverlap,
                ],
                'queue' => [
                    'ai_metadata_enqueued' => false,
                    'needs_ai_metadata' => $needsAiMetadata,
                ],
            ],
        ];
    }

    public function persistSnapshot(array $import): void
    {
        $directory = runtime_path('proofdb/imports');
        if (!is_dir($directory) && !mkdir($directory, 0775, true) && !is_dir($directory)) {
            throw new RuntimeException("Unable to create directory: {$directory}");
        }

        $path = $directory . DIRECTORY_SEPARATOR . $import['import_uid'] . '.json';
        $json = json_encode($import, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_THROW_ON_ERROR);

        if (file_put_contents($path, $json) === false) {
            throw new RuntimeException("Unable to write import snapshot: {$path}");
        }
    }

    private function validate(array $payload): array
    {
        $errors = [];

        if (isset($payload['file_error'])) {
            $errors['file'][] = 'uploaded file is invalid.';
        }

        if (!isset($payload['title']) || !is_string($payload['title']) || trim($payload['title']) === '') {
            $errors['title'][] = 'title is required.';
        }

        if (!isset($payload['source']) || !is_string($payload['source']) || trim($payload['source']) === '') {
            $errors['source'][] = 'source is required.';
        }

        if (!isset($payload['content']) && !isset($payload['paragraphs']) && !isset($payload['pages'])) {
            $errors['content'][] = 'content, file, pages, or paragraphs is required.';
        }

        if (isset($payload['paragraphs']) && !is_array($payload['paragraphs'])) {
            $errors['paragraphs'][] = 'paragraphs must be an array.';
        }

        if (isset($payload['pages']) && !is_array($payload['pages'])) {
            $errors['pages'][] = 'pages must be an array.';
        }

        if (isset($payload['metadata']) && !is_array($payload['metadata'])) {
            $errors['metadata'][] = 'metadata must be an object.';
        }

        $chunkSize = $this->intOption($payload, 'chunk_size', self::DEFAULT_CHUNK_SIZE);
        if ($chunkSize < self::MIN_CHUNK_SIZE || $chunkSize > self::MAX_CHUNK_SIZE) {
            $errors['chunk_size'][] = 'chunk_size must be between 100 and 4000.';
        }

        $chunkOverlap = $this->intOption($payload, 'chunk_overlap', self::DEFAULT_CHUNK_OVERLAP);
        if ($chunkOverlap < 0 || $chunkOverlap >= $chunkSize) {
            $errors['chunk_overlap'][] = 'chunk_overlap must be greater than or equal to 0 and less than chunk_size.';
        }

        if (!isset($errors['paragraphs']) && isset($payload['paragraphs'])) {
            $hasContent = false;
            foreach ($payload['paragraphs'] as $index => $paragraph) {
                $content = is_array($paragraph) ? ($paragraph['content'] ?? '') : $paragraph;
                if (!is_string($content)) {
                    $errors["paragraphs.{$index}.content"][] = 'paragraph content must be a string.';
                    continue;
                }
                if (trim($content) !== '') {
                    $hasContent = true;
                }
            }
            if (!$hasContent) {
                $errors['paragraphs'][] = 'paragraphs must contain at least one non-empty paragraph.';
            }
        }

        if (!isset($errors['pages']) && isset($payload['pages'])) {
            $hasContent = false;
            foreach ($payload['pages'] as $index => $page) {
                if (!is_array($page)) {
                    $errors["pages.{$index}"][] = 'page must be an object.';
                    continue;
                }

                if (!$this->hasPageNumber($page)) {
                    $errors["pages.{$index}.page_number"][] = 'page_number is required.';
                }

                if (!isset($page['content']) || !is_string($page['content'])) {
                    $errors["pages.{$index}.content"][] = 'page content must be a string.';
                    continue;
                }

                if (trim($page['content']) !== '') {
                    $hasContent = true;
                }

                if (isset($page['metadata']) && !is_array($page['metadata'])) {
                    $errors["pages.{$index}.metadata"][] = 'page metadata must be an object.';
                }
            }

            if (!$hasContent) {
                $errors['pages'][] = 'pages must contain at least one non-empty page.';
            }
        }

        if (isset($payload['content']) && (!is_string($payload['content']) || trim($payload['content']) === '')) {
            $errors['content'][] = 'content must be a non-empty string.';
        }

        return $errors;
    }

    private function archive(array $payload, string $archiveUid): array
    {
        $title = $this->clean($payload['title']);
        $source = $this->clean($payload['source']);

        return [
            'archive_uid' => $archiveUid,
            'title' => $title,
            'year' => isset($payload['year']) ? (int) $payload['year'] : null,
            'author' => $this->nullableClean($payload['author'] ?? null),
            'source' => $source,
            'series' => $this->nullableClean($payload['series'] ?? null),
            'tags' => is_array($payload['tags'] ?? null) ? array_values($payload['tags']) : [],
            'summary' => $this->nullableClean($payload['summary'] ?? null),
            'metadata' => $payload['metadata'] ?? [],
            'content' => $this->nullableClean($payload['content_url'] ?? $payload['content_path'] ?? null),
            'raw' => $this->nullableClean($payload['raw_url'] ?? $payload['raw_path'] ?? null),
        ];
    }

    private function pageBlocks(array $payload): array
    {
        if (isset($payload['pages'])) {
            return $this->pageBlocksFromPages($payload);
        }

        if (isset($payload['paragraphs'])) {
            return $this->pageBlocksFromItems($payload, $payload['paragraphs']);
        }

        return $this->pageBlocksFromItems($payload, preg_split('/\R{2,}/u', $payload['content']));
    }

    private function pageBlocksFromPages(array $payload): array
    {
        $pageBlocks = [];

        foreach ($payload['pages'] as $pageIndex => $page) {
            $pageNumber = $this->pageNumber($page);
            $pageMetadata = $page['metadata'] ?? [];
            $items = $this->markdownBlocksFromPage($page['content']);

            foreach ($items as $itemIndex => $content) {
                $pageBlock = $this->pageBlock($payload, $content, count($pageBlocks), $itemIndex, $pageNumber, [
                    'page_index' => $pageIndex,
                    'page_metadata' => $pageMetadata,
                ]);

                if ($pageBlock !== null) {
                    $pageBlocks[] = $pageBlock;
                }
            }
        }

        return $pageBlocks;
    }

    private function chunksFromPages(string $archiveUid, array $pageBlocks, int $chunkSize, int $chunkOverlap): array
    {
        $chunks = [];
        $chunkIndex = 1;

        foreach ($this->groupBlocksByPage($pageBlocks) as $pageNumber => $blocks) {
            $units = [];
            foreach ($blocks as $block) {
                $unit = $this->cleanEmbeddingText($block['content']);
                if ($unit === '' || $this->isNoiseBlock($unit)) {
                    continue;
                }

                $units[] = $unit;
            }

            foreach ($this->packUnitsForEmbedding($units, $chunkSize, $chunkOverlap) as $text) {
                $page = $this->restorePageNumber($pageNumber);
                $chunks[] = $this->chunk($archiveUid, $chunkIndex, $page, $text);
                $chunkIndex++;
            }
        }

        return $chunks;
    }

    private function groupBlocksByPage(array $pageBlocks): array
    {
        $pages = [];
        foreach ($pageBlocks as $block) {
            $key = $block['page_number'] === null ? '' : (string) $block['page_number'];
            $pages[$key][] = $block;
        }

        return $pages;
    }

    private function pagesSummary(array $pageBlocks, array $chunks): array
    {
        $pages = [];

        foreach ($this->groupBlocksByPage($pageBlocks) as $pageNumber => $blocks) {
            $page = $this->restorePageNumber($pageNumber);
            $pageChunks = array_values(array_filter($chunks, fn (array $chunk): bool => $chunk['page_start'] === $page));
            $contentLength = array_sum(array_map(fn (array $block): int => mb_strlen($block['content']), $blocks));

            $pages[] = [
                'page_number' => $page,
                'block_count' => count($blocks),
                'chunk_count' => count($pageChunks),
                'content_length' => $contentLength,
                'chunk_uids' => array_column($pageChunks, 'chunk_uid'),
            ];
        }

        return $pages;
    }

    private function packUnitsForEmbedding(array $units, int $chunkSize, int $chunkOverlap): array
    {
        $chunks = [];
        $current = '';

        foreach ($units as $unit) {
            $unit = $this->clean($unit);
            if ($unit === '') {
                continue;
            }

            if (mb_strlen($unit) > $chunkSize) {
                if ($current !== '') {
                    $chunks[] = $current;
                    $current = '';
                }

                array_push($chunks, ...$this->chunkLongUnit($unit, $chunkSize, $chunkOverlap));
                continue;
            }

            $candidate = $current === '' ? $unit : $current . "\n\n" . $unit;
            if (mb_strlen($candidate) <= $chunkSize) {
                $current = $candidate;
                continue;
            }

            if ($current !== '') {
                $chunks[] = $current;
            }
            $current = $unit;
        }

        if ($current !== '') {
            $chunks[] = $current;
        }

        return $chunks;
    }

    private function chunk(string $archiveUid, int $chunkIndex, int|string|null $pageNumber, string $text): array
    {
        $chunkUid = $this->chunkUid($archiveUid, $chunkIndex, implode('|', [
            $chunkIndex,
            (string) ($pageNumber ?? ''),
            $text,
        ]));

        return [
            'chunk_uid' => $chunkUid,
            'chunk_index' => $chunkIndex,
            'page_start' => $pageNumber,
            'page_end' => $pageNumber,
            'pages' => $pageNumber === null ? [] : [$pageNumber],
            'text' => $text,
            'length' => mb_strlen($text),
            'embedding_ref' => null,
        ];
    }

    private function normalizePayload(array $payload): array
    {
        if (isset($payload['content']) && is_string($payload['content']) && !isset($payload['pages']) && !isset($payload['paragraphs'])) {
            $payload['pages'] = $this->pagesFromMarkdown($payload['content']);
        }

        if (!isset($payload['source']) || trim((string) $payload['source']) === '') {
            $payload['source'] = 'raw-markdown';
        }

        return $payload;
    }

    private function applyMetadataFallbacks(array $payload): array
    {
        if ((!isset($payload['title']) || trim((string) $payload['title']) === '') && isset($payload['content']) && is_string($payload['content'])) {
            $payload['title'] = $this->inferTitle($payload['content'], (string) ($payload['source'] ?? ''));
            $payload['metadata'] = is_array($payload['metadata'] ?? null) ? $payload['metadata'] : [];
            $payload['metadata']['title_source'] = 'fallback';
        }

        if (isset($payload['tags']) && is_string($payload['tags'])) {
            $payload['tags'] = $this->tagsFromString($payload['tags']);
        }
        $payload['tags'] = is_array($payload['tags'] ?? null) ? $payload['tags'] : [];

        if (isset($payload['year']) && is_numeric($payload['year'])) {
            $payload['year'] = (int) $payload['year'];
        }

        $payload['metadata'] = is_array($payload['metadata'] ?? null) ? $payload['metadata'] : [];

        return $payload;
    }

    private function pagesFromMarkdown(string $markdown): array
    {
        preg_match_all(self::MARKDOWN_PAGE_PATTERN, $markdown, $matches, PREG_SET_ORDER);
        if ($matches === []) {
            return [[
                'page_number' => 1,
                'content' => $this->cleanMarkdownPage($markdown),
                'metadata' => ['parser' => 'markdown_single_page'],
            ]];
        }

        $pages = [];
        foreach ($matches as $index => $match) {
            $pageNumber = ctype_digit($match[1]) ? (int) $match[1] : $match[1];
            $pages[] = [
                'page_number' => $pageNumber,
                'content' => $this->cleanMarkdownPage($match[2]),
                'metadata' => [
                    'parser' => 'docmaster_markdown',
                    'page_index' => $index,
                ],
            ];
        }

        return $pages;
    }

    private function markdownBlocksFromPage(string $content): array
    {
        $content = $this->cleanMarkdownPage($content);
        $blocks = preg_split('/\R{2,}/u', $content, -1, PREG_SPLIT_NO_EMPTY);
        if ($blocks === false) {
            return [$content];
        }

        $records = [];
        foreach ($blocks as $block) {
            $block = $this->cleanMarkdownBlock($block);
            if ($block === '') {
                continue;
            }

            $lastIndex = count($records) - 1;
            if ($lastIndex >= 0 && $this->isCommentBlock($block) && $this->isPolicyRecordBlock($records[$lastIndex])) {
                $records[$lastIndex] .= "\n" . $block;
                continue;
            }

            $records[] = $block;
        }

        return $records;
    }

    private function cleanMarkdownPage(string $content): string
    {
        $content = preg_replace('/<!--\s*DOCMASTER:PAGE\s+[^>]+-->/iu', '', $content) ?? $content;
        $content = preg_replace('/^\s*#+\s*Page\s+\S+\s*$/imu', '', $content) ?? $content;
        $content = preg_replace('/^\s*---+\s*$/mu', '', $content) ?? $content;
        $content = html_entity_decode($content, ENT_QUOTES | ENT_HTML5, 'UTF-8');

        return trim($content);
    }

    private function cleanMarkdownBlock(string $block): string
    {
        $block = preg_replace('/[ \t]+/u', ' ', $block) ?? $block;
        $block = preg_replace('/\R[ \t]+/u', "\n", $block) ?? $block;
        return trim($block);
    }

    private function isCommentBlock(string $block): bool
    {
        return (bool) preg_match('/^\s*(?:[*#\s_~`>-])*COMMENT\b/iu', $this->plainBlock($block));
    }

    private function isPolicyRecordBlock(string $block): bool
    {
        return (bool) preg_match('/^\s*(?:NSAM|NSDM|NSDD|NSD|PD)\s+\d+/iu', $this->plainBlock($block));
    }

    private function isNoiseBlock(string $block): bool
    {
        $plain = strtoupper($this->plainBlock($block));
        $plain = preg_replace('/\s+/u', ' ', $plain) ?? $plain;

        if ($plain === '') {
            return true;
        }

        if (preg_match('/^\d{1,6}$/', $plain)) {
            return true;
        }

        $patterns = [
            '/^(?:# )?UNCLASSIFIED$/',
            '/^TOP SECRET$/',
            '/^UNCLASSIFIED WITH TOP SECRET ATTACHMENTS$/',
            '/^DECLASSIFY ON: OADR$/',
            '/^\*? ?UNCLASSIFIED\*?$/',
        ];

        foreach ($patterns as $pattern) {
            if (preg_match($pattern, $plain)) {
                return true;
            }
        }

        return false;
    }

    private function cleanEmbeddingText(string $text): string
    {
        $lines = preg_split('/\R/u', $text);
        if ($lines === false) {
            return $this->cleanMarkdownBlock($text);
        }

        $kept = [];
        foreach ($lines as $line) {
            $line = trim($line);
            if ($line === '' || $this->isNoiseLine($line)) {
                continue;
            }
            $kept[] = $line;
        }

        return $this->cleanMarkdownBlock(implode("\n", $kept));
    }

    private function isNoiseLine(string $line): bool
    {
        $plain = strtoupper($this->plainBlock($line));
        $plain = preg_replace('/\s+/u', ' ', $plain) ?? $plain;

        if ($plain === '' || preg_match('/^\d{1,6}$/', $plain)) {
            return true;
        }

        $patterns = [
            '/^(?:# )?UNCLASSIFIED$/',
            '/^TOP SECRET$/',
            '/^UNCLASSIFIED WITH TOP SECRET ATTACHMENTS$/',
            '/^DECLASSIFY ON: OADR$/',
            '/^PARTIALLY DECLASSIFIED\/RELEASED ON .+$/',
            '/^UNDER PROVISIONS OF .+$/',
            '/^BY .+ NATIONAL SECURITY COUNCIL$/',
            '/^F \d{2}-\d+$/',
        ];

        foreach ($patterns as $pattern) {
            if (preg_match($pattern, $plain)) {
                return true;
            }
        }

        return false;
    }

    private function plainBlock(string $block): string
    {
        $block = str_replace(['*', '_', '`', '~'], '', $block);
        $block = preg_replace('/\s+/u', ' ', $block) ?? $block;
        return trim($block);
    }

    private function inferTitle(string $markdown, string $source): string
    {
        if (preg_match_all('/^\s*#+\s*(.+?)\s*$/imu', $markdown, $matches)) {
            foreach ($matches[1] as $heading) {
                $heading = $this->clean($heading);
                if (!preg_match('/^Page\s+\S+$/iu', $heading) && !$this->isNoiseLine($heading)) {
                    return $heading;
                }
            }
        }

        if ($source !== '') {
            return pathinfo($source, PATHINFO_FILENAME) ?: $source;
        }

        return 'Untitled Markdown Import';
    }

    private function pageBlocksFromItems(array $payload, array $items): array
    {
        $pageBlocks = [];

        foreach ($items as $index => $item) {
            $content = is_array($item) ? ($item['content'] ?? '') : $item;
            $pageNumber = is_array($item) && $this->hasPageNumber($item) ? $this->pageNumber($item) : null;
            $metadata = is_array($item) ? ($item['metadata'] ?? []) : [];
            $pageBlock = $this->pageBlock($payload, $content, count($pageBlocks), $index, $pageNumber, $metadata);

            if ($pageBlock !== null) {
                $pageBlocks[] = $pageBlock;
            }
        }

        return $pageBlocks;
    }

    private function pageBlock(
        array $payload,
        mixed $content,
        int $blockIndex,
        int $sourceIndex,
        int|string|null $pageNumber,
        array $metadata
    ): ?array {
        $content = $this->clean((string) $content);
        if ($content === '') {
            return null;
        }

        return [
            'block_uid' => $this->uid('block', implode('|', [
                $payload['source'],
                $payload['title'],
                (string) $pageNumber,
                $sourceIndex,
                $content,
            ])),
            'index' => $blockIndex,
            'page_number' => $pageNumber,
            'content' => $content,
            'metadata' => $metadata,
        ];
    }

    private function chunkLongUnit(string $text, int $chunkSize, int $chunkOverlap): array
    {
        if (mb_strlen($text) <= $chunkSize) {
            return [$text];
        }

        $chunks = [];
        $current = '';

        foreach ($this->semanticUnits($text) as $unit) {
            if (mb_strlen($unit) > $chunkSize) {
                if ($current !== '') {
                    $chunks[] = $current;
                    $current = '';
                }

                array_push($chunks, ...$this->hardChunk($unit, $chunkSize, $chunkOverlap));
                continue;
            }

            $candidate = $current === '' ? $unit : $current . ' ' . $unit;
            if (mb_strlen($candidate) <= $chunkSize) {
                $current = $candidate;
                continue;
            }

            if ($current !== '') {
                $chunks[] = $current;
            }
            $current = $unit;
        }

        if ($current !== '') {
            $chunks[] = $current;
        }

        return $chunks === [] ? [$text] : $chunks;
    }

    private function semanticUnits(string $text): array
    {
        $units = preg_split(self::SENTENCE_BOUNDARY_PATTERN, $text, -1, PREG_SPLIT_NO_EMPTY);
        if ($units === false || $units === []) {
            return [$text];
        }

        return array_values(array_filter(array_map(fn (string $unit): string => $this->clean($unit), $units)));
    }

    private function hardChunk(string $text, int $chunkSize, int $chunkOverlap): array
    {
        $length = mb_strlen($text);
        if ($length <= $chunkSize) {
            return [$text];
        }

        $chunks = [];
        $start = 0;
        while ($start < $length) {
            $chunk = mb_substr($text, $start, $chunkSize);
            if ($chunk === '') {
                break;
            }

            $chunks[] = $chunk;
            if ($start + $chunkSize >= $length) {
                break;
            }

            $start += $chunkSize - $chunkOverlap;
        }

        return $chunks;
    }

    private function hasPageNumber(array $item): bool
    {
        return array_key_exists('page_number', $item)
            || array_key_exists('page', $item)
            || array_key_exists('number', $item);
    }

    private function pageNumber(array $item): int|string
    {
        $pageNumber = $item['page_number'] ?? $item['page'] ?? $item['number'];
        return is_int($pageNumber) ? $pageNumber : $this->clean((string) $pageNumber);
    }

    private function restorePageNumber(string $pageNumber): int|string|null
    {
        if ($pageNumber === '') {
            return null;
        }

        return ctype_digit($pageNumber) ? (int) $pageNumber : $pageNumber;
    }

    private function intOption(array $payload, string $key, int $default): int
    {
        if (!isset($payload[$key]) || $payload[$key] === '') {
            return $default;
        }

        return (int) $payload[$key];
    }

    private function clean(string $value): string
    {
        return trim(preg_replace('/[ \t]+/u', ' ', $value) ?? $value);
    }

    private function nullableClean(mixed $value): ?string
    {
        if (!is_string($value)) {
            return null;
        }

        $value = $this->clean($value);
        return $value === '' ? null : $value;
    }

    private function tagsFromString(string $value): array
    {
        $value = trim($value);
        if ($value === '') {
            return [];
        }

        $decoded = json_decode($value, true);
        if (is_array($decoded)) {
            return array_values(array_filter(array_map('strval', $decoded)));
        }

        return array_values(array_filter(array_map('trim', preg_split('/[,，]/u', $value) ?: [])));
    }

    private function archiveUid(array $payload): string
    {
        if (isset($payload['archive_uid']) && is_string($payload['archive_uid']) && $this->isUlid($payload['archive_uid'])) {
            return strtoupper($payload['archive_uid']);
        }

        return (string) new Ulid();
    }

    private function chunkUid(string $archiveUid, int $chunkIndex, string $value): string
    {
        return $archiveUid . '_' . $chunkIndex . '_' . $this->shortUid($value);
    }

    private function shortUid(string $value): string
    {
        $number = hexdec(substr(hash('crc32b', $value), 0, 8)) % 100000;
        return str_pad((string) $number, 5, '0', STR_PAD_LEFT);
    }

    private function isUlid(string $value): bool
    {
        return (bool) preg_match('/^[0-9A-HJKMNP-TV-Z]{26}$/', strtoupper($value));
    }

    private function uid(string $prefix, string $value): string
    {
        return $prefix . '_' . substr(hash('sha256', $value), 0, 24);
    }
}