"""
Unified Document Exporter Service

Provides standardized export functionality for UnifiedDocument,
supporting both OCR and Direct extraction track outputs with
comprehensive processing metadata.
"""

import json
import logging
from pathlib import Path
from typing import Dict, Any, Optional, Tuple, Union
from datetime import datetime

from ..models.unified_document import (
    UnifiedDocument,
    ProcessingTrack,
    ElementType
)

logger = logging.getLogger(__name__)


class ExportFormat:
    """Supported export formats"""
    JSON = "json"
    JSON_MINIMAL = "json_minimal"
    JSON_LEGACY = "json_legacy"
    MARKDOWN = "markdown"
    TEXT = "text"
    HTML = "html"


class UnifiedDocumentExporter:
    """
    Exporter service for UnifiedDocument with comprehensive metadata support.

    Supports both OCR and DIRECT processing tracks with consistent output format.
    """

    # Schema version for tracking format changes
    SCHEMA_VERSION = "1.0.0"

    @staticmethod
    def export_to_json(
        document: UnifiedDocument,
        output_path: Optional[Path] = None,
        include_metadata: bool = True,
        include_statistics: bool = True,
        include_binary_content: bool = False,
        pretty_print: bool = True
    ) -> Union[str, Path]:
        """
        Export UnifiedDocument to standardized JSON format.

        Args:
            document: The UnifiedDocument to export
            output_path: Optional path to save the JSON file
            include_metadata: Include processing metadata
            include_statistics: Include document statistics
            include_binary_content: Include base64-encoded binary content
            pretty_print: Format JSON with indentation

        Returns:
            JSON string if no output_path, otherwise the output Path
        """
        export_data = UnifiedDocumentExporter._build_export_data(
            document,
            include_metadata=include_metadata,
            include_statistics=include_statistics,
            include_binary_content=include_binary_content
        )

        json_str = json.dumps(
            export_data,
            ensure_ascii=False,
            indent=2 if pretty_print else None,
            default=str
        )

        if output_path:
            output_path = Path(output_path)
            output_path.parent.mkdir(parents=True, exist_ok=True)
            output_path.write_text(json_str, encoding='utf-8')
            logger.info(f"Exported JSON to: {output_path}")
            return output_path

        return json_str

    @staticmethod
    def export_to_markdown(
        document: UnifiedDocument,
        output_path: Optional[Path] = None,
        include_metadata_header: bool = True,
        include_page_breaks: bool = True
    ) -> Union[str, Path]:
        """
        Export UnifiedDocument to Markdown format.

        Args:
            document: The UnifiedDocument to export
            output_path: Optional path to save the Markdown file
            include_metadata_header: Include document metadata as header
            include_page_breaks: Include page break markers

        Returns:
            Markdown string if no output_path, otherwise the output Path
        """
        lines = []

        # Add metadata header
        if include_metadata_header:
            lines.append(f"# {document.metadata.filename}")
            lines.append("")
            lines.append("## Document Info")
            lines.append(f"- **Processing Track**: {document.metadata.processing_track.value}")
            lines.append(f"- **Processing Time**: {document.metadata.processing_time:.2f}s")
            lines.append(f"- **Pages**: {document.page_count}")
            lines.append(f"- **Total Elements**: {document.total_elements}")
            if document.metadata.language:
                lines.append(f"- **Language**: {document.metadata.language}")
            lines.append("")
            lines.append("---")
            lines.append("")

        # Export each page
        for page in document.pages:
            if include_page_breaks and page.page_number > 1:
                lines.append("")
                lines.append(f"---")
                lines.append("")

            lines.append(f"## Page {page.page_number}")
            lines.append("")

            # Get elements in reading order
            for element in page.get_reading_order():
                content = UnifiedDocumentExporter._element_to_markdown(element)
                if content:
                    lines.append(content)
                    lines.append("")

        md_content = "\n".join(lines)

        if output_path:
            output_path = Path(output_path)
            output_path.parent.mkdir(parents=True, exist_ok=True)
            output_path.write_text(md_content, encoding='utf-8')
            logger.info(f"Exported Markdown to: {output_path}")
            return output_path

        return md_content

    @staticmethod
    def export_to_text(
        document: UnifiedDocument,
        output_path: Optional[Path] = None,
        page_separator: str = "\n\n--- Page Break ---\n\n"
    ) -> Union[str, Path]:
        """
        Export UnifiedDocument to plain text format.

        Args:
            document: The UnifiedDocument to export
            output_path: Optional path to save the text file
            page_separator: Separator between pages

        Returns:
            Text string if no output_path, otherwise the output Path
        """
        pages_text = []

        for page in document.pages:
            page_text = page.extract_text()
            if page_text:
                pages_text.append(page_text)

        text_content = page_separator.join(pages_text)

        if output_path:
            output_path = Path(output_path)
            output_path.parent.mkdir(parents=True, exist_ok=True)
            output_path.write_text(text_content, encoding='utf-8')
            logger.info(f"Exported text to: {output_path}")
            return output_path

        return text_content

    @staticmethod
    def export_to_legacy_json(
        document: UnifiedDocument,
        output_path: Optional[Path] = None
    ) -> Union[str, Path]:
        """
        Export UnifiedDocument to legacy JSON format for backward compatibility.

        Args:
            document: The UnifiedDocument to export
            output_path: Optional path to save the JSON file

        Returns:
            JSON string if no output_path, otherwise the output Path
        """
        legacy_data = document.to_legacy_format()

        json_str = json.dumps(
            legacy_data,
            ensure_ascii=False,
            indent=2,
            default=str
        )

        if output_path:
            output_path = Path(output_path)
            output_path.parent.mkdir(parents=True, exist_ok=True)
            output_path.write_text(json_str, encoding='utf-8')
            logger.info(f"Exported legacy JSON to: {output_path}")
            return output_path

        return json_str

    @staticmethod
    def export_all_formats(
        document: UnifiedDocument,
        output_dir: Path,
        file_id: str
    ) -> Dict[str, Optional[Path]]:
        """
        Export UnifiedDocument to all standard formats.

        Args:
            document: The UnifiedDocument to export
            output_dir: Directory to save output files
            file_id: Base filename for outputs

        Returns:
            Dictionary mapping format names to output paths
        """
        output_dir = Path(output_dir)
        output_dir.mkdir(parents=True, exist_ok=True)

        results = {}

        # Export JSON
        try:
            json_path = output_dir / f"{file_id}_result.json"
            UnifiedDocumentExporter.export_to_json(
                document,
                json_path,
                include_metadata=True,
                include_statistics=True
            )
            results['json'] = json_path
        except Exception as e:
            logger.error(f"Failed to export JSON: {e}")
            results['json'] = None

        # Export Markdown
        try:
            md_path = output_dir / f"{file_id}_output.md"
            UnifiedDocumentExporter.export_to_markdown(document, md_path)
            results['markdown'] = md_path
        except Exception as e:
            logger.error(f"Failed to export Markdown: {e}")
            results['markdown'] = None

        # Export plain text
        try:
            txt_path = output_dir / f"{file_id}_text.txt"
            UnifiedDocumentExporter.export_to_text(document, txt_path)
            results['text'] = txt_path
        except Exception as e:
            logger.error(f"Failed to export text: {e}")
            results['text'] = None

        return results

    @staticmethod
    def _build_export_data(
        document: UnifiedDocument,
        include_metadata: bool = True,
        include_statistics: bool = True,
        include_binary_content: bool = False
    ) -> Dict[str, Any]:
        """
        Build the export data structure with processing metadata.

        Supports both OCR and DIRECT track outputs with consistent format.
        """
        # Base document data
        export_data = {
            "schema_version": UnifiedDocumentExporter.SCHEMA_VERSION,
            "document_id": document.document_id,
            "export_timestamp": datetime.utcnow().isoformat() + "Z"
        }

        # Add metadata
        if include_metadata:
            export_data["metadata"] = document.metadata.to_dict()

            # Add extended processing metadata
            export_data["metadata"]["processing_info"] = {
                "track_description": UnifiedDocumentExporter._get_track_description(
                    document.metadata.processing_track
                ),
                "schema_version": UnifiedDocumentExporter.SCHEMA_VERSION,
                "export_format": "unified_document_v1"
            }

        # Add pages
        export_data["pages"] = [page.to_dict() for page in document.pages]

        # Add statistics
        if include_statistics:
            export_data["statistics"] = {
                "page_count": document.page_count,
                "total_elements": document.total_elements,
                "total_tables": len(document.get_all_tables()),
                "total_images": len(document.get_all_images()),
                "element_type_counts": UnifiedDocumentExporter._count_element_types(document),
                "text_stats": UnifiedDocumentExporter._calculate_text_stats(document)
            }

        # Add processing errors if any
        if document.processing_errors:
            export_data["processing_errors"] = document.processing_errors

        return export_data

    @staticmethod
    def _get_track_description(track: ProcessingTrack) -> str:
        """Get human-readable description for processing track."""
        descriptions = {
            ProcessingTrack.OCR: "PaddleOCR PP-StructureV3 - Used for scanned documents and images",
            ProcessingTrack.DIRECT: "PyMuPDF Direct Extraction - Used for editable PDFs with embedded text",
            ProcessingTrack.HYBRID: "Hybrid Processing - Combined OCR and direct extraction"
        }
        return descriptions.get(track, "Unknown processing track")

    @staticmethod
    def _count_element_types(document: UnifiedDocument) -> Dict[str, int]:
        """Count occurrences of each element type in the document."""
        counts = {}
        for page in document.pages:
            for element in page.elements:
                type_name = element.type.value
                counts[type_name] = counts.get(type_name, 0) + 1
        return counts

    @staticmethod
    def _calculate_text_stats(document: UnifiedDocument) -> Dict[str, Any]:
        """Calculate text statistics for the document."""
        full_text = document.extract_all_text()
        words = full_text.split()
        chars = len(full_text)

        # Calculate average confidence
        confidences = []
        for page in document.pages:
            for element in page.elements:
                if element.confidence is not None:
                    confidences.append(element.confidence)

        avg_confidence = sum(confidences) / len(confidences) if confidences else None

        return {
            "total_characters": chars,
            "total_words": len(words),
            "average_confidence": round(avg_confidence, 4) if avg_confidence else None
        }

    @staticmethod
    def _element_to_markdown(element) -> str:
        """Convert a document element to Markdown format."""
        content = element.get_text()

        if not content and element.type not in [ElementType.TABLE, ElementType.IMAGE]:
            return ""

        # Format based on element type
        if element.type == ElementType.TITLE:
            return f"# {content}"
        elif element.type == ElementType.HEADER:
            return f"### {content}"
        elif element.type in [ElementType.TEXT, ElementType.PARAGRAPH, ElementType.BODY]:
            return content
        elif element.type == ElementType.LIST_ITEM:
            return f"- {content}"
        elif element.type == ElementType.TABLE:
            # Use HTML table if available
            if hasattr(element.content, 'to_html'):
                return element.content.to_html()
            return f"[Table: {content}]"
        elif element.type == ElementType.IMAGE:
            return f"![Image]({element.metadata.get('path', 'image')})"
        elif element.type == ElementType.FIGURE:
            return f"[Figure: {content or 'No caption'}]"
        elif element.type == ElementType.CODE:
            return f"```\n{content}\n```"
        elif element.type == ElementType.EQUATION:
            return f"$${content}$$"
        elif element.type == ElementType.CAPTION:
            return f"*{content}*"
        elif element.type == ElementType.FOOTNOTE:
            return f"[^{content}]"
        elif element.type == ElementType.REFERENCE:
            return f"> {content}"
        else:
            return content if content else ""


class JSONSchemaValidator:
    """
    Validator for UnifiedDocument JSON exports.

    Uses the JSON Schema definition to validate exported data.
    """

    _schema = None

    @classmethod
    def get_schema(cls) -> Dict[str, Any]:
        """Load and return the JSON Schema for UnifiedDocument."""
        if cls._schema is None:
            schema_path = Path(__file__).parent.parent / "schemas" / "unified_document_schema.json"
            if schema_path.exists():
                cls._schema = json.loads(schema_path.read_text(encoding='utf-8'))
            else:
                logger.warning(f"Schema file not found: {schema_path}")
                cls._schema = {}
        return cls._schema

    @classmethod
    def validate(cls, data: Dict[str, Any]) -> Tuple[bool, Optional[str]]:
        """
        Validate JSON data against the UnifiedDocument schema.

        Args:
            data: The JSON data to validate

        Returns:
            Tuple of (is_valid, error_message)
        """
        try:
            import jsonschema
            schema = cls.get_schema()
            if not schema:
                return True, None  # Skip validation if schema not available

            jsonschema.validate(data, schema)
            return True, None
        except ImportError:
            logger.warning("jsonschema package not installed, skipping validation")
            return True, None
        except Exception as e:
            return False, str(e)


def save_unified_document(
    document: UnifiedDocument,
    output_dir: Path,
    file_id: str,
    formats: Optional[list] = None
) -> Dict[str, Optional[Path]]:
    """
    Convenience function to save UnifiedDocument to multiple formats.

    Args:
        document: The UnifiedDocument to save
        output_dir: Output directory
        file_id: Base filename
        formats: List of formats to export (default: ['json', 'markdown'])

    Returns:
        Dictionary mapping format names to output paths
    """
    if formats is None:
        formats = ['json', 'markdown']

    results = {}
    output_dir = Path(output_dir)
    output_dir.mkdir(parents=True, exist_ok=True)

    for fmt in formats:
        try:
            if fmt == 'json':
                path = output_dir / f"{file_id}_result.json"
                UnifiedDocumentExporter.export_to_json(document, path)
                results['json'] = path
            elif fmt == 'markdown':
                path = output_dir / f"{file_id}_output.md"
                UnifiedDocumentExporter.export_to_markdown(document, path)
                results['markdown'] = path
            elif fmt == 'text':
                path = output_dir / f"{file_id}_text.txt"
                UnifiedDocumentExporter.export_to_text(document, path)
                results['text'] = path
            elif fmt == 'legacy':
                path = output_dir / f"{file_id}_legacy.json"
                UnifiedDocumentExporter.export_to_legacy_json(document, path)
                results['legacy'] = path
        except Exception as e:
            logger.error(f"Failed to export {fmt}: {e}")
            results[fmt] = None

    return results