<?php
declare(strict_types=1);

require_once __DIR__ . '/../includes/bootstrap.php';
require_once __DIR__ . '/../includes/DiscrepancyAgent.php';
require_once __DIR__ . '/../includes/ToolModels.php';

dbnToolsRequireMethod('POST');
dbnToolsRequireAuth();
$ftUid       = dbnToolsFreeTierCheck('discrepancy');

@ini_set('output_buffering', '0');
@ini_set('zlib.output_compression', '0');
@ini_set('implicit_flush', '1');
while (ob_get_level() > 0) { @ob_end_clean(); }
ob_implicit_flush(true);

header('Content-Type: application/x-ndjson; charset=utf-8');
header('Cache-Control: no-store');
header('X-Accel-Buffering: no');

$language  = 'en';
$startTime = microtime(true);

$emit = function (string $event, array $payload = []) use ($startTime): void {
    $payload['event'] = $event;
    $payload['t_ms']  = (int)round((microtime(true) - $startTime) * 1000);
    echo json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES) . "\n";
    @flush();
};

try {
    // Parse payload (always multipart — two files required)
    $payloadRaw = (string)($_POST['payload'] ?? '');
    if ($payloadRaw === '') {
        throw new DbnToolsHttpException('Missing payload field.', 422, 'missing_payload');
    }
    $input = json_decode($payloadRaw, true);
    if (!is_array($input)) {
        throw new DbnToolsHttpException('Invalid payload JSON.', 422, 'invalid_payload_json');
    }

    $language      = dbnToolsNormalizeLanguage($input['language'] ?? 'en');
    $engine        = ToolModels::engineForUser($ftUid, (string)($input['engine'] ?? 'azure_mini'));
    $sliceInput    = $input['slices'] ?? [];

    // Extract file A
    $emit('progress', ['detail' => 'Reading Document A…']);
    $fileEntryA = $_FILES['file_a'] ?? null;
    if (!$fileEntryA || ($fileEntryA['error'] ?? UPLOAD_ERR_NO_FILE) !== UPLOAD_ERR_OK) {
        throw new DbnToolsHttpException(
            'Document A is required. Upload a PDF, DOCX, or TXT file.',
            422, 'missing_file_a'
        );
    }
    $extractedA = dbnToolsExtractUploadedFile([
        'name'     => $fileEntryA['name']     ?? '',
        'type'     => $fileEntryA['type']     ?? '',
        'tmp_name' => $fileEntryA['tmp_name'] ?? '',
        'error'    => $fileEntryA['error']    ?? UPLOAD_ERR_NO_FILE,
        'size'     => $fileEntryA['size']     ?? 0,
    ]);
    $fileA = [
        'filename'  => $extractedA['filename'],
        'text'      => $extractedA['text'],
        'chars'     => $extractedA['chars'],
        'truncated' => $extractedA['truncated'],
    ];
    $emit('progress', ['detail' => sprintf('Document A extracted: %s (%d chars%s)',
        $extractedA['filename'], $extractedA['chars'],
        !empty($extractedA['truncated']) ? ', truncated' : '')]);

    // Extract file B
    $emit('progress', ['detail' => 'Reading Document B…']);
    $fileEntryB = $_FILES['file_b'] ?? null;
    if (!$fileEntryB || ($fileEntryB['error'] ?? UPLOAD_ERR_NO_FILE) !== UPLOAD_ERR_OK) {
        throw new DbnToolsHttpException(
            'Document B is required. Upload a PDF, DOCX, or TXT file.',
            422, 'missing_file_b'
        );
    }
    $extractedB = dbnToolsExtractUploadedFile([
        'name'     => $fileEntryB['name']     ?? '',
        'type'     => $fileEntryB['type']     ?? '',
        'tmp_name' => $fileEntryB['tmp_name'] ?? '',
        'error'    => $fileEntryB['error']    ?? UPLOAD_ERR_NO_FILE,
        'size'     => $fileEntryB['size']     ?? 0,
    ]);
    $fileB = [
        'filename'  => $extractedB['filename'],
        'text'      => $extractedB['text'],
        'chars'     => $extractedB['chars'],
        'truncated' => $extractedB['truncated'],
    ];
    $emit('progress', ['detail' => sprintf('Document B extracted: %s (%d chars%s)',
        $extractedB['filename'], $extractedB['chars'],
        !empty($extractedB['truncated']) ? ', truncated' : '')]);

    if (($fileA['text'] ?? '') === '') {
        throw new DbnToolsHttpException('Could not extract text from Document A.', 422, 'empty_file_a');
    }
    if (($fileB['text'] ?? '') === '') {
        throw new DbnToolsHttpException('Could not extract text from Document B.', 422, 'empty_file_b');
    }

    $emit('start', [
        'engine'   => $engine,
        'language' => $language,
        'file_a'   => $fileA['filename'],
        'file_b'   => $fileB['filename'],
    ]);

    // Optional: append the user's case-context as supplementary background to Doc A.
    $useMyCase = !empty($input['use_my_case']);
    if ($useMyCase) {
        $retrievalQuery = mb_substr((string)$fileA['text'], 0, 2000, 'UTF-8');
        $caseBlock = dbnToolsCaseContext(true, $retrievalQuery, 5);
        if ($caseBlock !== '') {
            $fileA['text'] .= "\n\n" . $caseBlock;
        }
    }

    $result = (new DbnDiscrepancyAgent())->run(
        $fileA,
        $fileB,
        $engine,
        $language,
        is_array($sliceInput) ? $sliceInput : [],
        $emit
    );

    $result['ok']         = true;
    $result['latency_ms'] = (int)round((microtime(true) - $startTime) * 1000);

    dbnToolsLogMetadata([
        'tool'           => 'discrepancy',
        'language'       => $language,
        'ok'             => true,
        'latency_ms'     => $result['latency_ms'],
        'source_count'   => (int)($result['trace_metadata']['source_count'] ?? 0),
        'conflict_count' => (int)($result['trace_metadata']['conflict_count'] ?? 0),
        'deleted_count'  => (int)($result['trace_metadata']['deleted_count'] ?? 0),
        'added_count'    => (int)($result['trace_metadata']['added_count'] ?? 0),
        'deployment'     => $result['trace_metadata']['deployment'] ?? null,
    ]);

    $ftRemaining = dbnToolsFreeTierDeduct($ftUid, 'discrepancy');
    if ($ftRemaining >= 0) {
        $result['balance'] = $ftRemaining;
    }

    $emit('final', ['result' => $result]);

} catch (DbnToolsHttpException $e) {
    $latency = (int)round((microtime(true) - $startTime) * 1000);
    dbnToolsLogMetadata([
        'tool'       => 'discrepancy',
        'language'   => $language,
        'ok'         => false,
        'latency_ms' => $latency,
        'error_code' => $e->errorCode,
    ]);
    $emit('error', ['code' => $e->errorCode, 'message' => $e->getMessage(), 'status' => $e->status]);
} catch (Throwable $e) {
    error_log('DBN discrepancy fatal: ' . $e->getMessage());
    $latency = (int)round((microtime(true) - $startTime) * 1000);
    dbnToolsLogMetadata([
        'tool'       => 'discrepancy',
        'language'   => $language,
        'ok'         => false,
        'latency_ms' => $latency,
        'error_code' => 'internal_error',
    ]);
    $emit('error', ['code' => 'internal_error', 'message' => 'The discrepancy finder could not complete this request.']);
}