"""
Evidence Building and Management

Creates and manages evidence references for extracted data.
Links every extraction to its visual source.
"""

import hashlib
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Dict, List, Optional, Union

from ..chunks.models import (
    BoundingBox,
    DocumentChunk,
    EvidenceRef,
    TableChunk,
    ChartChunk,
)


@dataclass
class EvidenceConfig:
    """Configuration for evidence building."""

    # Crop settings
    crop_enabled: bool = True
    crop_output_dir: Optional[Path] = None
    crop_format: str = "png"
    crop_padding_percent: float = 0.02  # 2% padding around bbox

    # Evidence settings
    include_snippet: bool = True
    max_snippet_length: int = 200
    include_context: bool = True
    context_chars: int = 50


class EvidenceBuilder:
    """
    Builds evidence references for extractions.

    Creates links between extracted values and their
    visual sources in the document.
    """

    def __init__(self, config: Optional[EvidenceConfig] = None):
        self.config = config or EvidenceConfig()
        self._crop_counter = 0

    def create_evidence(
        self,
        chunk: DocumentChunk,
        value: Any,
        field_name: Optional[str] = None,
        crop_image: Optional[Any] = None,
    ) -> EvidenceRef:
        """
        Create an evidence reference from a chunk.

        Args:
            chunk: Source chunk
            value: Extracted value
            field_name: Optional field name being extracted
            crop_image: Optional cropped image for this evidence

        Returns:
            EvidenceRef linking to the source
        """
        # Generate crop path if image provided
        crop_path = None
        if crop_image is not None and self.config.crop_enabled:
            crop_path = self._save_crop(crop_image, chunk)

        # Create snippet
        snippet = self._create_snippet(chunk.text, str(value))

        # Determine source type
        if isinstance(chunk, TableChunk):
            source_type = "table"
        elif isinstance(chunk, ChartChunk):
            source_type = "chart"
        else:
            source_type = chunk.chunk_type.value

        return EvidenceRef(
            chunk_id=chunk.chunk_id,
            doc_id=chunk.doc_id,
            page=chunk.page,
            bbox=chunk.bbox,
            source_type=source_type,
            snippet=snippet,
            confidence=chunk.confidence,
            crop_path=crop_path,
        )

    def create_evidence_from_bbox(
        self,
        doc_id: str,
        page: int,
        bbox: BoundingBox,
        source_text: str,
        confidence: float = 1.0,
        source_type: str = "region",
        crop_image: Optional[Any] = None,
    ) -> EvidenceRef:
        """
        Create evidence from a bounding box.

        Args:
            doc_id: Document ID
            page: Page number
            bbox: Bounding box of evidence
            source_text: Text content
            confidence: Confidence score
            source_type: Type of source (text, table, chart, etc.)
            crop_image: Optional cropped image

        Returns:
            EvidenceRef for the region
        """
        # Generate chunk_id for the region
        chunk_id = self._generate_region_id(doc_id, page, bbox)

        # Generate crop path if image provided
        crop_path = None
        if crop_image is not None and self.config.crop_enabled:
            crop_path = self._save_crop_direct(
                crop_image,
                doc_id,
                page,
                chunk_id,
            )

        return EvidenceRef(
            chunk_id=chunk_id,
            doc_id=doc_id,
            page=page,
            bbox=bbox,
            source_type=source_type,
            snippet=source_text[:self.config.max_snippet_length],
            confidence=confidence,
            crop_path=crop_path,
        )

    def create_table_cell_evidence(
        self,
        table_chunk: TableChunk,
        row: int,
        col: int,
        crop_image: Optional[Any] = None,
    ) -> Optional[EvidenceRef]:
        """
        Create evidence for a specific table cell.

        Args:
            table_chunk: Source table
            row: Cell row (0-indexed)
            col: Cell column (0-indexed)
            crop_image: Optional cropped cell image

        Returns:
            EvidenceRef for the cell, or None if cell not found
        """
        cell = table_chunk.get_cell(row, col)
        if cell is None:
            return None

        cell_id = f"r{row}c{col}"

        # Generate crop path
        crop_path = None
        if crop_image is not None and self.config.crop_enabled:
            crop_path = self._save_crop_direct(
                crop_image,
                table_chunk.doc_id,
                table_chunk.page,
                f"{table_chunk.chunk_id}_{cell_id}",
            )

        return EvidenceRef(
            chunk_id=table_chunk.chunk_id,
            doc_id=table_chunk.doc_id,
            page=table_chunk.page,
            bbox=cell.bbox,
            source_type="table_cell",
            snippet=cell.text[:self.config.max_snippet_length],
            confidence=cell.confidence,
            cell_id=cell_id,
            crop_path=crop_path,
        )

    def merge_evidence(
        self,
        evidence_list: List[EvidenceRef],
    ) -> List[EvidenceRef]:
        """
        Merge overlapping evidence references.

        Combines evidence that refers to the same region.
        """
        if len(evidence_list) <= 1:
            return evidence_list

        merged = []
        used = set()

        for i, ev1 in enumerate(evidence_list):
            if i in used:
                continue

            # Find overlapping evidence
            group = [ev1]
            for j, ev2 in enumerate(evidence_list[i + 1:], start=i + 1):
                if j in used:
                    continue

                if (ev1.doc_id == ev2.doc_id and
                    ev1.page == ev2.page and
                    ev1.bbox.iou(ev2.bbox) > 0.5):
                    group.append(ev2)
                    used.add(j)

            # Merge group
            if len(group) == 1:
                merged.append(ev1)
            else:
                merged.append(self._merge_evidence_group(group))

            used.add(i)

        return merged

    def _merge_evidence_group(
        self,
        group: List[EvidenceRef],
    ) -> EvidenceRef:
        """Merge a group of overlapping evidence."""
        # Take the one with highest confidence
        best = max(group, key=lambda e: e.confidence)

        # Merge bounding boxes
        merged_bbox = BoundingBox(
            x_min=min(e.bbox.x_min for e in group),
            y_min=min(e.bbox.y_min for e in group),
            x_max=max(e.bbox.x_max for e in group),
            y_max=max(e.bbox.y_max for e in group),
            normalized=best.bbox.normalized,
        )

        # Combine snippets
        snippets = list(set(e.snippet for e in group if e.snippet))
        combined_snippet = " | ".join(snippets)[:self.config.max_snippet_length]

        return EvidenceRef(
            chunk_id=best.chunk_id,
            doc_id=best.doc_id,
            page=best.page,
            bbox=merged_bbox,
            source_type=best.source_type,
            snippet=combined_snippet,
            confidence=max(e.confidence for e in group),
            cell_id=best.cell_id,
            crop_path=best.crop_path,
        )

    def _create_snippet(
        self,
        full_text: str,
        value: str,
    ) -> str:
        """Create a text snippet highlighting the value."""
        if not self.config.include_snippet:
            return ""

        # Try to find value in text
        value_lower = value.lower()
        text_lower = full_text.lower()

        idx = text_lower.find(value_lower)
        if idx >= 0 and self.config.include_context:
            # Add context around value
            start = max(0, idx - self.config.context_chars)
            end = min(len(full_text), idx + len(value) + self.config.context_chars)

            snippet = full_text[start:end]
            if start > 0:
                snippet = "..." + snippet
            if end < len(full_text):
                snippet = snippet + "..."

            return snippet[:self.config.max_snippet_length]

        # Return start of text
        return full_text[:self.config.max_snippet_length]

    def _generate_region_id(
        self,
        doc_id: str,
        page: int,
        bbox: BoundingBox,
    ) -> str:
        """Generate a stable ID for a region."""
        content = f"{doc_id}_{page}_{bbox.xyxy}"
        return hashlib.md5(content.encode()).hexdigest()[:16]

    def _save_crop(
        self,
        image: Any,
        chunk: DocumentChunk,
    ) -> Optional[str]:
        """Save a crop image for a chunk."""
        return self._save_crop_direct(
            image,
            chunk.doc_id,
            chunk.page,
            chunk.chunk_id,
        )

    def _save_crop_direct(
        self,
        image: Any,
        doc_id: str,
        page: int,
        identifier: str,
    ) -> Optional[str]:
        """Save a crop image directly."""
        if self.config.crop_output_dir is None:
            return None

        try:
            from PIL import Image
            import numpy as np

            # Convert to PIL if needed
            if isinstance(image, np.ndarray):
                pil_image = Image.fromarray(image)
            elif isinstance(image, Image.Image):
                pil_image = image
            else:
                return None

            # Create output path
            output_dir = Path(self.config.crop_output_dir)
            output_dir.mkdir(parents=True, exist_ok=True)

            filename = f"{doc_id}_{page}_{identifier}.{self.config.crop_format}"
            output_path = output_dir / filename

            pil_image.save(output_path)
            return str(output_path)

        except Exception:
            return None


class EvidenceTracker:
    """
    Tracks evidence references during extraction.

    Maintains a collection of evidence and provides
    methods for querying and validation.
    """

    def __init__(self):
        self._evidence: List[EvidenceRef] = []
        self._by_field: Dict[str, List[EvidenceRef]] = {}
        self._by_chunk: Dict[str, List[EvidenceRef]] = {}

    def add(
        self,
        evidence: EvidenceRef,
        field_name: Optional[str] = None,
    ) -> None:
        """Add an evidence reference."""
        self._evidence.append(evidence)

        # Index by chunk
        if evidence.chunk_id not in self._by_chunk:
            self._by_chunk[evidence.chunk_id] = []
        self._by_chunk[evidence.chunk_id].append(evidence)

        # Index by field
        if field_name:
            if field_name not in self._by_field:
                self._by_field[field_name] = []
            self._by_field[field_name].append(evidence)

    def get_all(self) -> List[EvidenceRef]:
        """Get all evidence references."""
        return self._evidence.copy()

    def get_for_field(self, field_name: str) -> List[EvidenceRef]:
        """Get evidence for a specific field."""
        return self._by_field.get(field_name, []).copy()

    def get_for_chunk(self, chunk_id: str) -> List[EvidenceRef]:
        """Get evidence from a specific chunk."""
        return self._by_chunk.get(chunk_id, []).copy()

    def get_by_page(self, page: int) -> List[EvidenceRef]:
        """Get evidence from a specific page."""
        return [e for e in self._evidence if e.page == page]

    def get_high_confidence(self, threshold: float = 0.8) -> List[EvidenceRef]:
        """Get evidence above confidence threshold."""
        return [e for e in self._evidence if e.confidence >= threshold]

    def validate_field(
        self,
        field_name: str,
        min_evidence: int = 1,
        min_confidence: float = 0.5,
    ) -> bool:
        """
        Validate that a field has sufficient evidence.

        Args:
            field_name: Field to validate
            min_evidence: Minimum number of evidence references
            min_confidence: Minimum confidence score

        Returns:
            True if field has sufficient evidence
        """
        field_evidence = self.get_for_field(field_name)

        if len(field_evidence) < min_evidence:
            return False

        # Check confidence
        max_confidence = max((e.confidence for e in field_evidence), default=0)
        return max_confidence >= min_confidence

    def clear(self) -> None:
        """Clear all evidence."""
        self._evidence = []
        self._by_field = {}
        self._by_chunk = {}