<?php

declare(strict_types=1);

namespace MageSail\Magesail\Model;

/**
 * Parses NGINX map blocks into structured data for GUI editing.
 */
class NginxMapParser
{
    /**
     * @return array{
     *     blocks: array<int, array{
     *         source: string,
     *         target: string,
     *         startLine: int,
     *         endLine: int,
     *         entries: array<int, array{
     *             hostname: string,
     *             value: string,
     *             line: int,
     *             comment?: string
     *         }>
     *     }>
     * }
     */
    public function parse(string $content): array
    {
        $lines = explode("\n", $content);
        $blocks = [];
        $i = 0;
        $len = \count($lines);
        while ($i < $len) {
            if (preg_match('/^\s*map\s+\$(\w+)\s+\$(\w+)\s*\{/', $lines[$i], $m)) {
                $block = [
                    'source' => $m[1],
                    'target' => $m[2],
                    'startLine' => $i,
                    'endLine' => $i,
                    'entries' => [],
                ];
                $openBrace = $i;
                $depth = 0;
                $inBlock = false;
                for ($j = $i; $j < $len; $j++) {
                    $line = $lines[$j];
                    if (str_contains($line, '{')) {
                        $depth++;
                        $inBlock = true;
                    }
                    if (str_contains($line, '}')) {
                        $depth--;
                        if ($depth === 0 && $inBlock) {
                            $block['endLine'] = $j;
                            break;
                        }
                    }
                    if ($inBlock && $j > $openBrace) {
                        $trimmed = trim($line);
                        if ($trimmed === '' || $trimmed === '}') {
                            continue;
                        }
                        if (preg_match('/^default\s+(\S+)\s*;\s*(.*)$/', $trimmed, $defaultMatch)) {
                            $block['default'] = trim($defaultMatch[1], '"\'');
                            continue;
                        }
                        if (preg_match('/^(\S+)\s+(\S+)\s*;\s*(.*)$/', $trimmed, $entry)) {
                            $hostname = trim($entry[1], '"\'');
                            $value = trim($entry[2], '"\'');
                            $comment = trim($entry[3] ?? '');
                            $block['entries'][] = [
                                'hostname' => $hostname,
                                'value' => $value,
                                'line' => $j,
                                'comment' => $comment !== '' ? $comment : null,
                            ];
                        }
                    }
                }
                if ($block['endLine'] > $block['startLine']) {
                    $blocks[] = $block;
                }
                $i = $block['endLine'] + 1;
            } else {
                $i++;
            }
        }
        return ['blocks' => $blocks];
    }

    /**
     * Rebuild file content from parsed blocks, preserving non-map content and original map order/position.
     *
     * Each block must include startLine, endLine from {@see parse()} (GUI saves merge file metadata with edited entries).
     */
    public function rebuild(string $originalContent, array $parsedBlocks): string
    {
        $lines = explode("\n", $originalContent);
        $len = \count($lines);
        /** @var array<int, array<string, mixed>> $blockAtLine */
        $blockAtLine = [];
        foreach ($parsedBlocks['blocks'] as $block) {
            if (!isset($block['startLine'], $block['endLine'])) {
                throw new \InvalidArgumentException(
                    'Each map block must include startLine and endLine (re-parse the file or use merged save data).'
                );
            }
            $blockAtLine[(int) $block['startLine']] = $block;
        }
        ksort($blockAtLine, SORT_NUMERIC);
        $output = [];
        $i = 0;
        while ($i < $len) {
            if (isset($blockAtLine[$i])) {
                $block = $blockAtLine[$i];
                foreach ($this->renderMapBlockLines($lines, $block) as $line) {
                    $output[] = $line;
                }
                $i = (int) $block['endLine'] + 1;
                continue;
            }
            $output[] = $lines[$i];
            $i++;
        }
        return implode("\n", $output);
    }

    /**
     * @param array<string, mixed> $block
     * @return list<string>
     */
    private function renderMapBlockLines(array $fileLines, array $block): array
    {
        $start = (int) $block['startLine'];
        $indent = $this->detectIndent($fileLines, $start);
        $out = [];
        $out[] = sprintf('%smap $%s $%s {', $indent, $block['source'], $block['target']);
        $defaultValue = $block['default'] ?? "''";
        $out[] = sprintf('%s        default %s;', $indent, $defaultValue);
        foreach ($block['entries'] as $entry) {
            if (!\is_array($entry)) {
                continue;
            }
            $hostname = $this->escapeIfNeeded((string) ($entry['hostname'] ?? ''));
            $value = $this->escapeIfNeeded((string) ($entry['value'] ?? ''));
            $comment = !empty($entry['comment']) ? ' ' . (string) $entry['comment'] : '';
            $out[] = sprintf('%s        %s %s;%s', $indent, $hostname, $value, $comment);
        }
        $out[] = $indent . '}';
        return $out;
    }

    private function detectIndent(array $lines, int $lineNum): string
    {
        if ($lineNum < \count($lines)) {
            $line = $lines[$lineNum];
            if (preg_match('/^(\s*)/', $line, $m)) {
                return $m[1];
            }
        }
        return '';
    }

    private function escapeIfNeeded(string $value): string
    {
        if (preg_match('/^[a-zA-Z0-9._-]+$/', $value)) {
            return $value;
        }
        return '"' . addcslashes($value, '"\\') . '"';
    }
}