from __future__ import annotations

import datetime
import time
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any

from ocr_pipeline.citations import extract_citations
from ocr_pipeline.config import settings
from ocr_pipeline.detectors import detect_figures, detect_tables
from ocr_pipeline.ocr import ImagePreprocessor, OCREngine, compute_image_hash
from ocr_pipeline.ocr.parallel import ParallelProcessor
from ocr_pipeline.output import MarkdownWriter
from ocr_pipeline.postprocess import chunk_text, clean_text, extract_entities
from ocr_pipeline.utils.db import Database, get_db
from ocr_pipeline.utils.logging import get_logger
from ocr_pipeline.watch import Watcher

logger = get_logger(__name__)


@dataclass
class PipelineResult:
    total_images: int = 0
    successful: int = 0
    failed: int = 0
    skipped: int = 0
    chunks_created: int = 0
    output_files: list[Path] = field(default_factory=list)
    errors: list[dict[str, str]] = field(default_factory=list)


class OCRPipeline:
    def __init__(self) -> None:
        self.engine = OCREngine()
        self.preprocessor = ImagePreprocessor()
        self.writer = MarkdownWriter()
        self.db: Database = get_db()
        self._run_id: int | None = None

    def _process_single(self, image_path: Path) -> list[Path]:
        image_hash = compute_image_hash(image_path)
        if settings.processing.skip_existing and self.db.is_processed(image_hash, image_path):
            logger.info("already_processed", path=str(image_path))
            return []

        original_image = self.preprocessor.load_image(image_path)
        # PaddleOCR reads the (size-capped) original; Tesseract the binarized derivative.
        ocr_base = self.preprocessor.resize_if_needed(original_image)
        preprocessed = self.preprocessor.preprocess_image(original_image)
        ocr_result = self.engine.process(ocr_base, preprocessed)
        cleaned = clean_text(ocr_result.text)
        chunks = chunk_text(cleaned.text)
        entities = extract_entities(cleaned.text)
        # Detectors receive the original image: binarization/line removal damages their inputs.
        figures = detect_figures(original_image)
        tables = detect_tables(original_image)
        citations = extract_citations(cleaned.text)
        timestamp = datetime.datetime.now(datetime.UTC).isoformat()

        output_files: list[Path] = []
        for chunk in chunks:
            metadata = {
                "source_path": str(image_path),
                "source_hash": image_hash,
                "timestamp": timestamp,
                "ocr_engine": ocr_result.engine,
                "ocr_confidence_mean": ocr_result.confidence,
                "language": ocr_result.language,
                "entity_extraction_backend": entities.backend,
                "detected_entities": [entity.text for entity in entities.entities],
                "has_figures": bool(figures),
                "has_tables": bool(tables),
                "citations_found": [
                    f"{citation.type}:{citation.identifier}" for citation in citations
                ],
                "chunk_index": chunk.chunk_index,
                "total_chunks": len(chunks),
            }
            output_files.append(
                self.writer.write_chunk(
                    content=chunk.content,
                    metadata=metadata,
                    figures=figures,
                    tables=tables,
                    entities=entities,
                    citations=citations,
                )
            )

        self.db.mark_processed(
            file_hash=image_hash,
            path=str(image_path),
            timestamp=time.time(),
            engine=ocr_result.engine,
            confidence=ocr_result.confidence,
            chunks=len(chunks),
            run_id=self._run_id,
        )
        return output_files

    def process_single(self, image_path: Path) -> list[Path]:
        """Public single-image API used by notebook migration and watch mode."""
        return self._process_single(image_path)

    def process_all(self, image_paths: list[Path] | None = None) -> PipelineResult:
        if image_paths is None:
            image_paths = ParallelProcessor().find_images()
        else:
            image_paths = [path for path in image_paths if path.exists()]
        result = PipelineResult(total_images=len(image_paths))
        if not image_paths:
            return result

        run_timestamp = datetime.datetime.now(datetime.UTC).isoformat()
        self._run_id, run_number = self.db.start_run()
        self.writer.start_run(run_timestamp, run_number)
        try:
            # Output/database writes are deliberately centralized to avoid collisions and SQLite contention.
            for path in image_paths:
                try:
                    outputs = self._process_single(path)
                    if not outputs and settings.processing.skip_existing:
                        result.skipped += 1
                    else:
                        result.successful += 1
                        result.chunks_created += len(outputs)
                        result.output_files.extend(outputs)
                except Exception as exc:
                    result.failed += 1
                    result.errors.append({"path": str(path), "error": str(exc)})
                    logger.exception("pipeline_failed", path=str(path))
            if settings.output.write_consolidated:
                consolidated = self.writer.write_consolidated()
                if consolidated is not None:
                    result.output_files.append(consolidated)
        finally:
            self.db.complete_run(
                self._run_id,
                {
                    "total": result.total_images,
                    "successful": result.successful,
                    "failed": result.failed,
                    "chunks": result.chunks_created,
                },
            )
            self._run_id = None
        return result

    def watch(self) -> None:
        def process_callback(path: Path) -> None:
            self.process_single(path)

        watcher = Watcher(process_callback)
        watcher.start()
        try:
            while True:
                time.sleep(1)
        except KeyboardInterrupt:
            watcher.stop()

    def get_stats(self, days: int = 30) -> dict[str, Any]:
        return self.db.get_stats(days)