"""
DocuLens — Export endpoints.

Provides CSV and JSON export of extraction results
from pipeline runs stored in Supabase.
"""

import csv
import io
import json
import logging

from fastapi import APIRouter, HTTPException, Depends, Query
from fastapi.responses import StreamingResponse

from middleware import check_rate_limit

logger = logging.getLogger(__name__)

export_router = APIRouter()


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------

def _get_run_data(run_id: str) -> dict:
    """Fetch extraction_data from a pipeline run."""
    from db.supabase import get_client
    client = get_client()
    if not client:
        raise HTTPException(status_code=503, detail="Database not configured")

    resp = (
        client.table("pipeline_runs")
        .select("id, use_case, extraction_data, overall_result, processing_time_ms, started_at")
        .eq("id", run_id)
        .execute()
    )
    if not resp.data:
        raise HTTPException(status_code=404, detail=f"Run '{run_id}' not found")
    return resp.data[0]


def _flatten_fields(data: dict) -> dict:
    """Extract flat key-value fields from extraction_data."""
    fields = {}

    # extracted_fields (primary — works for all use cases)
    if "extracted_fields" in data and isinstance(data["extracted_fields"], dict):
        for k, v in data["extracted_fields"].items():
            fields[k] = v

    # Legacy named fields (invoice-specific)
    skip_keys = {
        "line_items", "bounding_boxes", "extracted_fields",
        "extraction_method", "model_id", "page_image",
        "page_images", "processing_time_ms", "confidence",
        "document_type", "raw_text",
    }
    for k, v in data.items():
        if k not in skip_keys and k not in fields and not isinstance(v, (dict, list)):
            fields[k] = v

    return fields


def _extraction_to_csv(data: dict) -> str:
    """Convert extraction data to CSV string."""
    output = io.StringIO()

    # Section 1: Header fields
    fields = _flatten_fields(data)
    if fields:
        writer = csv.writer(output)
        writer.writerow(["Field", "Value"])
        for k, v in fields.items():
            writer.writerow([k, v])
        output.write("\n")

    # Section 2: Line items
    line_items = data.get("line_items", [])
    if line_items:
        # Collect all unique keys across line items
        all_keys = []
        seen = set()
        for item in line_items:
            if isinstance(item, dict):
                for k in item.keys():
                    if k not in seen:
                        all_keys.append(k)
                        seen.add(k)

        writer = csv.writer(output)
        writer.writerow(all_keys)
        for item in line_items:
            if isinstance(item, dict):
                writer.writerow([item.get(k, "") for k in all_keys])

    return output.getvalue()


def _extraction_to_json(data: dict, run_meta: dict) -> dict:
    """Structure extraction data for JSON export."""
    fields = _flatten_fields(data)
    return {
        "run_id": run_meta.get("id"),
        "use_case": run_meta.get("use_case"),
        "status": run_meta.get("overall_result"),
        "processed_at": run_meta.get("started_at"),
        "processing_time_ms": run_meta.get("processing_time_ms"),
        "document_type": data.get("document_type", ""),
        "confidence": data.get("confidence", 0),
        "fields": fields,
        "line_items": data.get("line_items", []),
    }


# ---------------------------------------------------------------------------
# Endpoints
# ---------------------------------------------------------------------------

@export_router.get("/api/v1/runs/{run_id}/export")
async def export_run(
    run_id: str,
    format: str = Query("json", regex="^(json|csv)$"),
    api_key: str = Depends(check_rate_limit),
):
    """
    Export extraction results from a pipeline run.

    Query params:
      - format: "json" (default) or "csv"
    """
    run = _get_run_data(run_id)
    data = run.get("extraction_data") or {}

    if not data:
        raise HTTPException(status_code=404, detail="No extraction data for this run")

    if format == "csv":
        csv_content = _extraction_to_csv(data)
        return StreamingResponse(
            io.BytesIO(csv_content.encode("utf-8")),
            media_type="text/csv",
            headers={
                "Content-Disposition": f'attachment; filename="run_{run_id[:8]}.csv"',
            },
        )
    else:
        export_data = _extraction_to_json(data, run)
        json_content = json.dumps(export_data, indent=2, default=str)
        return StreamingResponse(
            io.BytesIO(json_content.encode("utf-8")),
            media_type="application/json",
            headers={
                "Content-Disposition": f'attachment; filename="run_{run_id[:8]}.json"',
            },
        )


@export_router.post("/api/v1/export/inline")
async def export_inline(
    data: dict,
    format: str = Query("json", regex="^(json|csv)$"),
    api_key: str = Depends(check_rate_limit),
):
    """
    Export extraction data directly (without a saved run).
    Accepts the extraction result JSON in the request body.

    Useful for exporting results from in-progress extractions
    that haven't been persisted yet.
    """
    if format == "csv":
        csv_content = _extraction_to_csv(data)
        return StreamingResponse(
            io.BytesIO(csv_content.encode("utf-8")),
            media_type="text/csv",
            headers={
                "Content-Disposition": 'attachment; filename="extraction.csv"',
            },
        )
    else:
        fields = _flatten_fields(data)
        export_data = {
            "document_type": data.get("document_type", ""),
            "confidence": data.get("confidence", 0),
            "fields": fields,
            "line_items": data.get("line_items", []),
        }
        json_content = json.dumps(export_data, indent=2, default=str)
        return StreamingResponse(
            io.BytesIO(json_content.encode("utf-8")),
            media_type="application/json",
            headers={
                "Content-Disposition": 'attachment; filename="extraction.json"',
            },
        )