// ============================================================================
// app/api/ocr/utils/imageRotation.ts
// PDF 페이지 처리 기능이 추가된 이미지 회전 유틸리티
// ============================================================================

import sharp from 'sharp';
import { promises as fs } from 'fs';
import path from 'path';
import { randomUUID } from 'crypto';
import { execFile } from 'child_process';
import { promisify } from 'util';
import { tmpdir } from 'os';

const exec = promisify(execFile);

/**
 * PDF 페이지 수를 확인하는 함수
 */
export async function getPDFPageCount(pdfBuffer: Buffer): Promise<number> {
  const tmp = tmpdir();
  const id = randomUUID();
  const pdfPath = path.join(tmp, `${id}.pdf`);
  
  try {
    await fs.writeFile(pdfPath, pdfBuffer);
    
    // pdfinfo 명령어로 페이지 수 확인
    const { stdout } = await exec('pdfinfo', [pdfPath]);
    const pageMatch = stdout.match(/Pages:\s+(\d+)/);
    const pageCount = pageMatch ? parseInt(pageMatch[1]) : 1;
    
    console.log(`📄 PDF has ${pageCount} pages`);
    return pageCount;
    
  } catch (error) {
    console.warn('❌ Could not get PDF page count, trying alternative method:', error);
    
    // pdfinfo가 실패하면 pdftoppm으로 테스트
    try {
      await exec('pdftoppm', ['-l', '1', '-null', pdfPath]);
      return 1; // 최소 1페이지는 있음
    } catch {
      console.warn('⚠️ Could not determine page count, assuming 1 page');
      return 1;
    }
  } finally {
    await fs.rm(pdfPath, { force: true }).catch(() => {});
  }
}

/**
 * base64 데이터 유효성 검증
 */
export function validateBase64Image(base64: string): { isValid: boolean; error?: string; size?: number } {
    try {
        if (!base64 || typeof base64 !== 'string') {
            return { isValid: false, error: 'Base64 data is empty or invalid type' };
        }

        const cleanBase64 = base64.replace(/^data:image\/[a-z]+;base64,/, '');

        if (!/^[A-Za-z0-9+/]*={0,2}$/.test(cleanBase64)) {
            return { isValid: false, error: 'Invalid base64 format' };
        }

        if (cleanBase64.length < 100) {
            return { isValid: false, error: `Base64 too short: ${cleanBase64.length} characters` };
        }

        const buffer = Buffer.from(cleanBase64, 'base64');
        const bufferSize = buffer.length;

        if (bufferSize < 1) {
            return { isValid: false, error: `Buffer too small: ${bufferSize} bytes` };
        }

        if (bufferSize > 52428800) { // 50MB
            return { isValid: false, error: `Buffer too large: ${bufferSize} bytes (max: 50MB)` };
        }

        return { isValid: true, size: bufferSize };

    } catch (error) {
        return {
            isValid: false,
            error: `Base64 validation failed: ${error instanceof Error ? error.message : 'Unknown error'}`
        };
    }
}

/**
 * 서버 사이드에서 이미지를 회전시킵니다
 */
export async function rotateImageBase64(base64: string, degrees: number): Promise<string> {
    try {
        console.log(`🔄 === ROTATING IMAGE BY ${degrees}° ===`);

        const validation = validateBase64Image(base64);
        if (!validation.isValid) {
            throw new Error(`Invalid input base64: ${validation.error}`);
        }

        console.log(`✅ Input validation passed - size: ${validation.size} bytes`);

        const cleanBase64 = base64.replace(/^data:image\/[a-z]+;base64,/, '');
        const inputBuffer = Buffer.from(cleanBase64, 'base64');

        console.log(`📊 Input buffer created: ${inputBuffer.length} bytes`);

        const normalizedDegrees = ((degrees % 360) + 360) % 360;
        console.log(`📐 Normalized rotation: ${normalizedDegrees}°`);

        let rotatedBuffer: Buffer;

        if (normalizedDegrees === 0) {
            console.log('  ↻ No rotation needed, applying quality enhancement...');
            rotatedBuffer = await sharp(inputBuffer)
                .jpeg({
                    quality: 90,
                    progressive: true,
                    mozjpeg: true
                })
                .toBuffer();
        } else {
            console.log(`  🔄 Applying ${normalizedDegrees}° rotation...`);

            const sharpInstance = sharp(inputBuffer);
            const metadata = await sharpInstance.metadata();
            console.log(`  📏 Original image: ${metadata.width}x${metadata.height}, format: ${metadata.format}`);

            rotatedBuffer = await sharpInstance
                .rotate(normalizedDegrees)
                .jpeg({
                    quality: 90,
                    progressive: true,
                    mozjpeg: true
                })
                .toBuffer();
        }

        console.log(`📊 Output buffer created: ${rotatedBuffer.length} bytes`);

        if (rotatedBuffer.length === 0) {
            throw new Error('Rotation resulted in empty buffer');
        }

        if (rotatedBuffer.length > 52428800) {
            throw new Error(`Rotated image too large: ${rotatedBuffer.length} bytes`);
        }

        const rotatedBase64 = rotatedBuffer.toString('base64');

        const outputValidation = validateBase64Image(rotatedBase64);
        if (!outputValidation.isValid) {
            throw new Error(`Invalid output base64: ${outputValidation.error}`);
        }

        console.log(`✅ Image rotated successfully: ${outputValidation.size} bytes`);
        console.log(`📈 Size change: ${inputBuffer.length} → ${outputValidation.size} bytes`);

        return rotatedBase64;

    } catch (error) {
        console.error(`❌ Error rotating image by ${degrees}°:`, error);

        if (error instanceof Error) {
            if (error.message.includes('Input buffer contains unsupported image format')) {
                console.error('  🖼️ Unsupported image format - try converting to JPEG first');
            } else if (error.message.includes('Input image exceeds pixel limit')) {
                console.error('  📏 Image too large for processing');
            } else if (error.message.includes('premature close')) {
                console.error('  🔧 Corrupted image data');
            }
        }

        const originalValidation = validateBase64Image(base64);
        if (originalValidation.isValid) {
            console.warn('  ↩️ Using original image due to rotation error');
            return base64;
        } else {
            throw new Error(`Rotation failed and original image is invalid: ${originalValidation.error}`);
        }
    }
}

/**
 * 이미지 품질을 개선합니다
 */
export async function enhanceImageQuality(base64: string): Promise<string> {
    try {
        console.log('🎨 === ENHANCING IMAGE QUALITY ===');

        const validation = validateBase64Image(base64);
        if (!validation.isValid) {
            console.warn(`⚠️ Invalid input for enhancement: ${validation.error}`);
            return base64;
        }

        console.log(`✅ Enhancement input valid: ${validation.size} bytes`);

        const cleanBase64 = base64.replace(/^data:image\/[a-z]+;base64,/, '');
        const inputBuffer = Buffer.from(cleanBase64, 'base64');

        const sharpInstance = sharp(inputBuffer);
        const metadata = await sharpInstance.metadata();

        console.log(`📏 Original: ${metadata.width}x${metadata.height}, ${metadata.format}`);

        const maxDimension = 2000;
        let needsResize = false;

        if (metadata.width && metadata.height) {
            needsResize = metadata.width > maxDimension || metadata.height > maxDimension;
        }

        let enhancedBuffer: Buffer;

        if (needsResize) {
            console.log(`📐 Resizing to fit ${maxDimension}px...`);
            enhancedBuffer = await sharpInstance
                .resize(maxDimension, maxDimension, {
                    fit: 'inside',
                    withoutEnlargement: true
                })
                .sharpen(0.5, 1, 2)
                .normalize()
                .gamma(1.1)
                .jpeg({
                    quality: 95,
                    progressive: true,
                    mozjpeg: true
                })
                .toBuffer();
        } else {
            console.log('📐 No resize needed, applying enhancement only...');
            enhancedBuffer = await sharpInstance
                .sharpen(0.5, 1, 2)
                .normalize()
                .gamma(1.1)
                .jpeg({
                    quality: 95,
                    progressive: true,
                    mozjpeg: true
                })
                .toBuffer();
        }

        const enhancedBase64 = enhancedBuffer.toString('base64');

        const outputValidation = validateBase64Image(enhancedBase64);
        if (!outputValidation.isValid) {
            console.warn(`⚠️ Enhancement resulted in invalid image: ${outputValidation.error}`);
            return base64;
        }

        console.log(`✅ Image enhanced: ${validation.size} → ${outputValidation.size} bytes`);
        return enhancedBase64;

    } catch (error) {
        console.error('❌ Error enhancing image:', error);
        return base64;
    }
}

/**
 * PDF를 이미지로 변환합니다 (개선된 버전)
 */
export async function convertPDFToImage(
  pdfBuffer: Buffer,
  pageIndex = 0,
  dpi = 300,
): Promise<string> {
  const tmp = tmpdir();
  const id = randomUUID();
  const pdfPath = path.join(tmp, `${id}.pdf`);
  const outPrefix = path.join(tmp, id);
  const jpgPath = `${outPrefix}.jpg`;

  try {
    console.log(`📄 Converting PDF page ${pageIndex + 1} to image (${dpi} DPI)...`);
    
    // 1) PDF 임시 저장
    await fs.writeFile(pdfPath, pdfBuffer);

    // 2) pdftoppm 실행
    const page = pageIndex + 1; // pdftoppm은 1-based
    await exec('pdftoppm', [
      '-jpeg',
      '-singlefile',
      '-r', dpi.toString(),
      '-f', page.toString(),
      '-l', page.toString(),
      pdfPath,
      outPrefix,
    ], { maxBuffer: 1024 * 1024 * 50 }); // 50MB 버퍼

    // 3) 결과 읽어 base64 변환
    const img = await fs.readFile(jpgPath);
    const base64 = img.toString('base64');
    
    console.log(`✅ PDF page ${pageIndex + 1} converted successfully: ${img.length} bytes`);
    
    return base64;

  } catch (error) {
    console.error(`❌ Error converting PDF page ${pageIndex + 1}:`, error);
    throw new Error(`Failed to convert PDF page ${pageIndex + 1}: ${error instanceof Error ? error.message : 'Unknown error'}`);
  } finally {
    // 4) 임시 파일 정리
    await fs.rm(pdfPath, { force: true }).catch(() => {});
    await fs.rm(jpgPath, { force: true }).catch(() => {});
  }
}

/**
 * 파일 형식을 JPEG로 정규화
 */
export async function normalizeImageFormat(base64: string): Promise<string> {
    try {
        console.log('🔄 Normalizing image format to JPEG...');

        const validation = validateBase64Image(base64);
        if (!validation.isValid) {
            throw new Error(`Cannot normalize invalid image: ${validation.error}`);
        }

        const cleanBase64 = base64.replace(/^data:image\/[a-z]+;base64,/, '');
        const inputBuffer = Buffer.from(cleanBase64, 'base64');

        const normalizedBuffer = await sharp(inputBuffer)
            .jpeg({
                quality: 90,
                progressive: true
            })
            .toBuffer();

        const normalizedBase64 = normalizedBuffer.toString('base64');

        const outputValidation = validateBase64Image(normalizedBase64);
        if (!outputValidation.isValid) {
            throw new Error(`Normalization failed: ${outputValidation.error}`);
        }

        console.log(`✅ Format normalized: ${validation.size} → ${outputValidation.size} bytes`);
        return normalizedBase64;

    } catch (error) {
        console.error('❌ Error normalizing image format:', error);
        throw error;
    }
}

// 기존 함수들
export async function detectTextOrientation(base64: string): Promise<number> {
    console.log('🧭 Detecting text orientation...');

    const rotations = [0, 90, 180, 270];
    const scores: { rotation: number; score: number }[] = [];

    for (const rotation of rotations) {
        try {
            const rotatedBase64 = await rotateImageBase64(base64, rotation);
            const score = await estimateTextQuality(rotatedBase64);
            scores.push({ rotation, score });

            console.log(`  ${rotation}°: quality score = ${score.toFixed(3)}`);

        } catch (error) {
            console.warn(`  ${rotation}°: Failed to test orientation`);
            scores.push({ rotation, score: 0 });
        }
    }

    const bestOrientation = scores.reduce((best, current) =>
        current.score > best.score ? current : best
    );

    console.log(`🎯 Best orientation detected: ${bestOrientation.rotation}°`);
    return bestOrientation.rotation;
}

async function estimateTextQuality(base64: string): Promise<number> {
    try {
        const cleanBase64 = base64.replace(/^data:image\/[a-z]+;base64,/, '');
        const buffer = Buffer.from(cleanBase64, 'base64');

        const stats = await sharp(buffer)
            .greyscale()
            .stats();

        const contrast = stats.channels[0].max - stats.channels[0].min;
        const sharpness = stats.channels[0].stdev;

        return (contrast + sharpness) / 510;

    } catch (error) {
        return 0;
    }
}

export async function needsRotation(base64: string): Promise<boolean> {
    try {
        const cleanBase64 = base64.replace(/^data:image\/[a-z]+;base64,/, '');
        const buffer = Buffer.from(cleanBase64, 'base64');

        const metadata = await sharp(buffer).metadata();

        if (metadata.orientation && metadata.orientation > 1) {
            console.log(`📐 EXIF orientation detected: ${metadata.orientation}`);
            return true;
        }

        if (metadata.width && metadata.height) {
            const aspectRatio = metadata.width / metadata.height;
            if (aspectRatio > 1.5) {
                console.log(`📐 Wide aspect ratio detected: ${aspectRatio.toFixed(2)}`);
                return true;
            }
        }

        return false;

    } catch (error) {
        console.warn('Error checking if rotation needed:', error);
        return false;
    }
}