"""Main OCR service coordinating preprocessing, recognition, and extraction."""

import os
import re
import logging

# Disable PaddleOCR model source check for faster startup (PaddleX 3.x) - must be set before import
os.environ['PADDLE_PDX_DISABLE_MODEL_SOURCE_CHECK'] = 'True'

import time
import asyncio
from concurrent.futures import ThreadPoolExecutor
from decimal import Decimal
from pathlib import Path
from typing import Optional, Tuple

from backend.modules.data_entry.services.ocr_engine import OCREngine
from backend.modules.data_entry.services.ocr_extractor import ReceiptExtractor, ExtractionResult
from backend.modules.data_entry.services.image_preprocessor import ImagePreprocessor

# Setup logging
logger = logging.getLogger(__name__)


class OCRService:
    """Service for OCR processing of receipt images."""

    _executor = ThreadPoolExecutor(max_workers=2)

    def __init__(self):
        self.preprocessor = ImagePreprocessor()
        self.ocr_engine = OCREngine()
        self.extractor = ReceiptExtractor()

    async def process_image(
        self,
        image_path: Path,
        mime_type: str
    ) -> Tuple[bool, str, Optional[ExtractionResult]]:
        """
        Process receipt image and extract structured data.

        Args:
            image_path: Path to the image file
            mime_type: MIME type of the file

        Returns:
            Tuple of (success, message, extraction_result)
        """
        try:
            loop = asyncio.get_event_loop()
            result = await loop.run_in_executor(
                self._executor,
                self._process_sync,
                image_path,
                mime_type
            )
            return result
        except Exception as e:
            return False, f"OCR processing failed: {str(e)}", None

    def _process_sync(
        self,
        image_path: Path,
        mime_type: str
    ) -> Tuple[bool, str, Optional[ExtractionResult]]:
        """Synchronous processing with ADAPTIVE OCR pipeline."""

        start_time = time.time()
        print(f"[OCR Service] Starting processing: {image_path}, mime: {mime_type}", flush=True)

        # Load image
        if mime_type == 'application/pdf':
            try:
                images = self.preprocessor.pdf_to_images(image_path)
                if not images:
                    return False, "Failed to extract images from PDF", None
                image = images[0]
            except RuntimeError as e:
                return False, str(e), None
        else:
            try:
                image = self.preprocessor.load_image(image_path)
            except ValueError as e:
                return False, str(e), None

        raw_texts = []
        extraction = None

        # ══════════════════════════════════════════════════════════════
        # STEP 1: PaddleOCR + Light (fastest, best for clear PDFs)
        # ══════════════════════════════════════════════════════════════
        print("=" * 60, flush=True)
        print("[OCR] STEP 1: PaddleOCR + Light preprocessing", flush=True)
        print("=" * 60, flush=True)
        light_img = self.preprocessor.preprocess_light(image)

        try:
            paddle_light = self.ocr_engine._paddle_recognize(light_img)
            if paddle_light and paddle_light.text:
                extraction = self.extractor.extract(paddle_light.text)
                extraction.ocr_engine = "paddle-light"
                raw_texts.append(f"═══ PaddleOCR (light, conf: {paddle_light.confidence:.0%}) ═══\n{paddle_light.text}")

                # Log extraction results
                print(f"[OCR] Step 1 Results:", flush=True)
                print(f"  - OCR Confidence: {paddle_light.confidence:.0%}", flush=True)
                print(f"  - Amount: {extraction.amount}", flush=True)
                print(f"  - Date: {extraction.receipt_date}", flush=True)
                print(f"  - Number: {extraction.receipt_number}", flush=True)
                print(f"  - CUI: {extraction.cui}", flush=True)
                print(f"  - TVA: {extraction.tva_total} (entries: {len(extraction.tva_entries) if extraction.tva_entries else 0})", flush=True)
                print(f"  - Overall Confidence: {extraction.overall_confidence:.0%}", flush=True)

                # Early exit if complete
                if self._is_extraction_complete(extraction):
                    extraction.raw_text = "\n\n".join(raw_texts)
                    elapsed_ms = int((time.time() - start_time) * 1000)
                    extraction.processing_time_ms = elapsed_ms
                    print(f"[OCR] ✓✓✓ EARLY EXIT at Step 1 - All fields found! ({elapsed_ms}ms) ✓✓✓", flush=True)
                    return True, "OCR complete (fast mode)", extraction
                else:
                    print("[OCR] → Step 1 incomplete, continuing to Step 2...", flush=True)
        except Exception as e:
            print(f"[OCR] PaddleOCR light failed: {e}", flush=True)
            extraction = ExtractionResult()

        # ══════════════════════════════════════════════════════════════
        # STEP 2: PaddleOCR + Heavy (for faded thermal receipts)
        # ══════════════════════════════════════════════════════════════
        print("=" * 60, flush=True)
        print("[OCR] STEP 2: PaddleOCR + Heavy preprocessing", flush=True)
        print("=" * 60, flush=True)
        heavy_img = self.preprocessor.preprocess_heavy(image)

        try:
            paddle_heavy = self.ocr_engine._paddle_recognize(heavy_img)
            if paddle_heavy and paddle_heavy.text:
                extraction_heavy = self.extractor.extract(paddle_heavy.text)
                extraction_heavy.ocr_engine = "paddle-heavy"
                raw_texts.append(f"═══ PaddleOCR (heavy, conf: {paddle_heavy.confidence:.0%}) ═══\n{paddle_heavy.text}")

                print(f"[OCR] Step 2 (Heavy) Results:", flush=True)
                print(f"  - OCR Confidence: {paddle_heavy.confidence:.0%}", flush=True)
                print(f"  - Amount: {extraction_heavy.amount}", flush=True)
                print(f"  - Date: {extraction_heavy.receipt_date}", flush=True)
                print(f"  - CUI: {extraction_heavy.cui}", flush=True)

                # Merge with previous
                extraction = self._merge_extractions(extraction, extraction_heavy)

                print(f"[OCR] After merge:", flush=True)
                print(f"  - Amount: {extraction.amount}", flush=True)
                print(f"  - Date: {extraction.receipt_date}", flush=True)
                print(f"  - Number: {extraction.receipt_number}", flush=True)
                print(f"  - CUI: {extraction.cui}", flush=True)
                print(f"  - TVA: {extraction.tva_total}", flush=True)
                print(f"  - Overall Confidence: {extraction.overall_confidence:.0%}", flush=True)

                if self._is_extraction_complete(extraction):
                    extraction.raw_text = "\n\n".join(raw_texts)
                    extraction.ocr_engine = "paddle-adaptive"
                    elapsed_ms = int((time.time() - start_time) * 1000)
                    extraction.processing_time_ms = elapsed_ms
                    print(f"[OCR] ✓✓✓ EARLY EXIT at Step 2 - All fields found after merge! ({elapsed_ms}ms) ✓✓✓", flush=True)
                    return True, "OCR complete (paddle dual)", extraction
                else:
                    print("[OCR] → Step 2 incomplete, continuing to Step 3 (Tesseract)...", flush=True)
        except Exception as e:
            print(f"[OCR] PaddleOCR heavy failed: {e}", flush=True)

        # ══════════════════════════════════════════════════════════════
        # STEP 3: Tesseract - ONLY to complete missing fields
        # Uses Tesseract-optimized preprocessing (binarized, high contrast)
        # ══════════════════════════════════════════════════════════════
        print("=" * 60, flush=True)
        print("[OCR] STEP 3: Tesseract (complement only, not override)", flush=True)
        print("=" * 60, flush=True)

        try:
            # Use Tesseract-specific preprocessing (Otsu binarization)
            tesseract_img = self.preprocessor.preprocess_for_tesseract(image)
            tesseract_result = self.ocr_engine._tesseract_recognize(tesseract_img)
            if tesseract_result and tesseract_result.text:
                extraction_tess = self.extractor.extract(tesseract_result.text)
                extraction_tess.ocr_engine = "tesseract"
                raw_texts.append(f"═══ Tesseract (conf: {tesseract_result.confidence:.0%}) ═══\n{tesseract_result.text}")

                print(f"[OCR] Step 3 (Tesseract) Results:", flush=True)
                print(f"  - OCR Confidence: {tesseract_result.confidence:.0%}", flush=True)
                print(f"  - Amount: {extraction_tess.amount}", flush=True)
                print(f"  - Date: {extraction_tess.receipt_date}", flush=True)
                print(f"  - CUI: {extraction_tess.cui}", flush=True)

                # IMPORTANT: Tesseract only COMPLETES missing fields, never overrides!
                extraction = self._complement_extraction(extraction, extraction_tess)
        except Exception as e:
            print(f"[OCR] Tesseract failed: {e}", flush=True)

        # ══════════════════════════════════════════════════════════════
        # FINAL VALIDATION: Fix impossible values
        # ══════════════════════════════════════════════════════════════
        if extraction:
            extraction = self._final_validation(extraction)

        # Final result
        if extraction is None:
            return False, "No text detected", None

        extraction.raw_text = "\n\n".join(raw_texts)
        extraction.ocr_engine = "adaptive-full"

        # Build result message
        fields_found = []
        if extraction.amount: fields_found.append("amount")
        if extraction.receipt_date: fields_found.append("date")
        if extraction.receipt_number: fields_found.append("number")
        if extraction.cui: fields_found.append("CUI")
        if extraction.tva_total or extraction.tva_entries: fields_found.append("TVA")

        message = f"OCR complete (full pipeline). Found: {', '.join(fields_found) or 'no fields'}"

        elapsed_ms = int((time.time() - start_time) * 1000)
        extraction.processing_time_ms = elapsed_ms

        print("=" * 60, flush=True)
        print(f"[OCR] FINAL RESULT (full pipeline) - {elapsed_ms}ms", flush=True)
        print("=" * 60, flush=True)
        print(f"  - Amount: {extraction.amount}", flush=True)
        print(f"  - Date: {extraction.receipt_date}", flush=True)
        print(f"  - Number: {extraction.receipt_number}", flush=True)
        print(f"  - CUI: {extraction.cui}", flush=True)
        print(f"  - TVA: {extraction.tva_total}", flush=True)
        print(f"  - Overall Confidence: {extraction.overall_confidence:.0%}", flush=True)
        print(f"  - Processing Time: {elapsed_ms}ms", flush=True)
        print(f"  - Message: {message}", flush=True)

        return True, message, extraction

    def _merge_extractions(
        self,
        paddle: Optional[ExtractionResult],
        tesseract: Optional[ExtractionResult]
    ) -> ExtractionResult:
        """
        Merge two extractions, picking best fields from each engine.

        Strategy:
        - For each field, prefer the one with higher confidence
        - Use validation rules (CUI format, date validity, company indicators)
        - Combine TVA entries if different
        """
        result = ExtractionResult()

        # Handle case where one is None
        if paddle is None and tesseract is None:
            return result
        if paddle is None:
            return tesseract
        if tesseract is None:
            return paddle

        print("[Merge] Comparing PaddleOCR vs Tesseract extractions...", flush=True)

        # === AMOUNT ===
        # Pick higher confidence, both must be positive
        if paddle.amount and tesseract.amount:
            if paddle.confidence_amount >= tesseract.confidence_amount:
                result.amount = paddle.amount
                result.confidence_amount = paddle.confidence_amount
                print(f"[Merge] Amount: PaddleOCR {paddle.amount} (conf: {paddle.confidence_amount:.0%})", flush=True)
            else:
                result.amount = tesseract.amount
                result.confidence_amount = tesseract.confidence_amount
                print(f"[Merge] Amount: Tesseract {tesseract.amount} (conf: {tesseract.confidence_amount:.0%})", flush=True)
        elif paddle.amount:
            result.amount = paddle.amount
            result.confidence_amount = paddle.confidence_amount
        elif tesseract.amount:
            result.amount = tesseract.amount
            result.confidence_amount = tesseract.confidence_amount

        # === DATE ===
        # Pick higher confidence, validate date reasonableness
        if paddle.receipt_date and tesseract.receipt_date:
            if paddle.confidence_date >= tesseract.confidence_date:
                result.receipt_date = paddle.receipt_date
                result.confidence_date = paddle.confidence_date
                print(f"[Merge] Date: PaddleOCR {paddle.receipt_date}", flush=True)
            else:
                result.receipt_date = tesseract.receipt_date
                result.confidence_date = tesseract.confidence_date
                print(f"[Merge] Date: Tesseract {tesseract.receipt_date}", flush=True)
        elif paddle.receipt_date:
            result.receipt_date = paddle.receipt_date
            result.confidence_date = paddle.confidence_date
        elif tesseract.receipt_date:
            result.receipt_date = tesseract.receipt_date
            result.confidence_date = tesseract.confidence_date

        # === VENDOR NAME ===
        # Prefer one with company indicators (S.R.L., S.A., etc.)
        paddle_has_indicator = self._has_company_indicator(paddle.partner_name)
        tesseract_has_indicator = self._has_company_indicator(tesseract.partner_name)

        if paddle.partner_name and tesseract.partner_name:
            if paddle_has_indicator and not tesseract_has_indicator:
                result.partner_name = paddle.partner_name
                result.confidence_vendor = paddle.confidence_vendor
                print(f"[Merge] Vendor: PaddleOCR '{paddle.partner_name}' (has company indicator)", flush=True)
            elif tesseract_has_indicator and not paddle_has_indicator:
                result.partner_name = tesseract.partner_name
                result.confidence_vendor = tesseract.confidence_vendor
                print(f"[Merge] Vendor: Tesseract '{tesseract.partner_name}' (has company indicator)", flush=True)
            elif paddle.confidence_vendor >= tesseract.confidence_vendor:
                result.partner_name = paddle.partner_name
                result.confidence_vendor = paddle.confidence_vendor
                print(f"[Merge] Vendor: PaddleOCR '{paddle.partner_name}' (higher conf)", flush=True)
            else:
                result.partner_name = tesseract.partner_name
                result.confidence_vendor = tesseract.confidence_vendor
                print(f"[Merge] Vendor: Tesseract '{tesseract.partner_name}' (higher conf)", flush=True)
        elif paddle.partner_name:
            result.partner_name = paddle.partner_name
            result.confidence_vendor = paddle.confidence_vendor
        elif tesseract.partner_name:
            result.partner_name = tesseract.partner_name
            result.confidence_vendor = tesseract.confidence_vendor

        # === CUI (Fiscal Code) ===
        # Validate format: 6-10 digits, prefer valid one
        paddle_cui_valid = self._is_valid_cui(paddle.cui)
        tesseract_cui_valid = self._is_valid_cui(tesseract.cui)

        if paddle.cui and tesseract.cui:
            if paddle_cui_valid and not tesseract_cui_valid:
                result.cui = paddle.cui
                print(f"[Merge] CUI: PaddleOCR {paddle.cui} (valid format)", flush=True)
            elif tesseract_cui_valid and not paddle_cui_valid:
                result.cui = tesseract.cui
                print(f"[Merge] CUI: Tesseract {tesseract.cui} (valid format)", flush=True)
            else:
                # Both valid or both invalid - prefer PaddleOCR
                result.cui = paddle.cui
                print(f"[Merge] CUI: PaddleOCR {paddle.cui}", flush=True)
        elif paddle.cui and paddle_cui_valid:
            result.cui = paddle.cui
        elif tesseract.cui and tesseract_cui_valid:
            result.cui = tesseract.cui
        elif paddle.cui:
            result.cui = paddle.cui
        elif tesseract.cui:
            result.cui = tesseract.cui

        # === TVA ENTRIES ===
        # Prefer non-empty, use the one with more entries or higher amounts
        if paddle.tva_entries and tesseract.tva_entries:
            # Compare: prefer the one with actual amounts (not just 0)
            paddle_total = sum(e.get('amount', Decimal('0')) for e in paddle.tva_entries)
            tesseract_total = sum(e.get('amount', Decimal('0')) for e in tesseract.tva_entries)

            if paddle_total >= tesseract_total:
                result.tva_entries = paddle.tva_entries
                result.tva_total = paddle.tva_total
                print(f"[Merge] TVA: PaddleOCR (total: {paddle_total})", flush=True)
            else:
                result.tva_entries = tesseract.tva_entries
                result.tva_total = tesseract.tva_total
                print(f"[Merge] TVA: Tesseract (total: {tesseract_total})", flush=True)
        elif paddle.tva_entries:
            result.tva_entries = paddle.tva_entries
            result.tva_total = paddle.tva_total
        elif tesseract.tva_entries:
            result.tva_entries = tesseract.tva_entries
            result.tva_total = tesseract.tva_total

        # === OTHER FIELDS ===
        # Simple preference: paddle > tesseract
        result.receipt_number = paddle.receipt_number or tesseract.receipt_number
        result.receipt_series = paddle.receipt_series or tesseract.receipt_series
        result.receipt_type = paddle.receipt_type or tesseract.receipt_type
        result.items_count = paddle.items_count or tesseract.items_count
        result.address = paddle.address or tesseract.address
        result.description = paddle.description or tesseract.description

        return result

    def _has_company_indicator(self, name: Optional[str]) -> bool:
        """Check if vendor name has company type indicator (S.R.L., S.A., etc.)"""
        if not name:
            return False
        name_upper = name.upper()
        indicators = [
            r'\bS\.?\s*R\.?\s*L\.?\b',
            r'\bS\.?\s*A\.?\b',
            r'\bS\.?\s*N\.?\s*C\.?\b',
            r'\bP\.?\s*F\.?\s*A\.?\b',
            r'\bI\.?\s*I\.?\b',
            r'\bHOLDING\b',
            r'\bGROUP\b',
            r'\bCOMPANY\b',
        ]
        for indicator in indicators:
            if re.search(indicator, name_upper):
                return True
        return False

    def _is_valid_cui(self, cui: Optional[str]) -> bool:
        """Validate CUI format: 6-10 digits."""
        if not cui:
            return False
        # Remove any RO prefix
        cui_clean = re.sub(r'^RO', '', cui.upper())
        # Must be 6-10 digits
        return bool(re.match(r'^\d{6,10}$', cui_clean))

    def _is_extraction_complete(self, ext: ExtractionResult, min_confidence: float = 0.85) -> bool:
        """
        Check if extraction has ALL required fields to skip further processing.

        Required for early exit (ALL must be true):
        - Overall confidence >= 85%
        - ALL 5 critical fields present: number, date, amount, TVA, CUI
        """
        # Must have high confidence
        if ext.overall_confidence < min_confidence:
            print(f"[OCR] Confidence {ext.overall_confidence:.0%} < {min_confidence:.0%} - continuing", flush=True)
            return False

        # Check all required fields
        has_number = bool(ext.receipt_number)
        has_date = bool(ext.receipt_date)
        has_amount = bool(ext.amount)
        has_tva = bool(ext.tva_total) or bool(ext.tva_entries)
        has_cui = bool(ext.cui)

        missing = []
        if not has_number: missing.append("number")
        if not has_date: missing.append("date")
        if not has_amount: missing.append("amount")
        if not has_tva: missing.append("TVA")
        if not has_cui: missing.append("CUI")

        if missing:
            print(f"[OCR] Missing: {', '.join(missing)} - continuing", flush=True)
            return False

        print(f"[OCR] ✓ All 5 fields found with {ext.overall_confidence:.0%} confidence", flush=True)
        return True

    def _complement_extraction(
        self,
        primary: Optional[ExtractionResult],
        secondary: Optional[ExtractionResult]
    ) -> ExtractionResult:
        """
        Complement primary extraction with missing fields from secondary.
        NEVER overrides existing values - only fills in gaps.

        This is different from _merge_extractions which can override values.
        """
        if primary is None and secondary is None:
            return ExtractionResult()
        if primary is None:
            return secondary
        if secondary is None:
            return primary

        print("[Complement] Adding missing fields from Tesseract...", flush=True)

        # Only fill missing amount
        if not primary.amount and secondary.amount:
            primary.amount = secondary.amount
            primary.confidence_amount = secondary.confidence_amount
            print(f"[Complement] Added amount: {secondary.amount}", flush=True)

        # Only fill missing date
        if not primary.receipt_date and secondary.receipt_date:
            primary.receipt_date = secondary.receipt_date
            primary.confidence_date = secondary.confidence_date
            print(f"[Complement] Added date: {secondary.receipt_date}", flush=True)

        # Only fill missing vendor
        if not primary.partner_name and secondary.partner_name:
            primary.partner_name = secondary.partner_name
            primary.confidence_vendor = secondary.confidence_vendor
            print(f"[Complement] Added vendor: {secondary.partner_name}", flush=True)

        # Only fill missing CUI
        if not primary.cui and secondary.cui and self._is_valid_cui(secondary.cui):
            primary.cui = secondary.cui
            print(f"[Complement] Added CUI: {secondary.cui}", flush=True)

        # Only fill missing TVA
        if not primary.tva_entries and secondary.tva_entries:
            primary.tva_entries = secondary.tva_entries
            primary.tva_total = secondary.tva_total
            print(f"[Complement] Added TVA: {secondary.tva_total}", flush=True)

        # Only fill missing receipt number
        if not primary.receipt_number and secondary.receipt_number:
            primary.receipt_number = secondary.receipt_number
            print(f"[Complement] Added number: {secondary.receipt_number}", flush=True)

        # Only fill missing address
        if not primary.address and secondary.address:
            primary.address = secondary.address
            print(f"[Complement] Added address: {secondary.address}", flush=True)

        return primary

    def _final_validation(self, extraction: ExtractionResult) -> ExtractionResult:
        """
        Final validation and correction of impossible values.

        Key rules:
        1. TVA cannot be greater than TOTAL (it's always a fraction)
        2. If TVA > TOTAL, recalculate TOTAL from TVA using known rates
        3. Validate TVA entries sum equals TVA total
        """
        print("[Final Validation] Checking extracted values...", flush=True)

        # Rule 1: TVA cannot be greater than TOTAL
        if extraction.tva_total and extraction.amount:
            if extraction.tva_total > extraction.amount:
                print(f"[Final Validation] TVA ({extraction.tva_total}) > TOTAL ({extraction.amount}) - IMPOSSIBLE!", flush=True)

                # Calculate TOTAL from TVA using reverse formula:
                # total = base + tva = tva * (100/rate + 1) = tva * (100 + rate) / rate
                # For 9% TVA: total = tva * 109 / 9 = tva * 12.11
                # For 19% TVA: total = tva * 119 / 19 = tva * 6.26
                # For 21% TVA: total = tva * 121 / 21 = tva * 5.76

                rate = 19  # Default rate assumption
                if extraction.tva_entries:
                    # Use the rate from the first entry
                    rate = extraction.tva_entries[0].get('percent', 19)

                if rate > 0:
                    # Formula: total = tva * (100 + rate) / rate
                    calculated_total = extraction.tva_total * (Decimal('100') + Decimal(str(rate))) / Decimal(str(rate))
                    calculated_total = calculated_total.quantize(Decimal('0.01'))

                    print(f"[Final Validation] Calculated TOTAL from TVA: {calculated_total} (using {rate}% rate)", flush=True)

                    extraction.amount = calculated_total
                    extraction.confidence_amount = 0.70  # Lower confidence for calculated value

        # Rule 2: TVA cannot be more than ~25% of total (max Romanian rate is 21%)
        if extraction.tva_total and extraction.amount:
            tva_percent = extraction.tva_total / extraction.amount * Decimal('100')
            if tva_percent > Decimal('25'):
                print(f"[Final Validation] Warning: TVA is {tva_percent:.1f}% of total - suspicious", flush=True)

        # Rule 3: Validate TVA entries sum
        if extraction.tva_entries and extraction.tva_total:
            entries_sum = sum(e.get('amount', Decimal('0')) for e in extraction.tva_entries)
            tolerance = Decimal('0.05')
            if abs(entries_sum - extraction.tva_total) > tolerance:
                print(f"[Final Validation] TVA entries sum ({entries_sum}) != tva_total ({extraction.tva_total})", flush=True)
                # Use the sum as it's more reliable
                extraction.tva_total = entries_sum

        print(f"[Final Validation] Done. Amount={extraction.amount}, TVA={extraction.tva_total}", flush=True)
        return extraction


# Singleton instance
ocr_service = OCRService()