"""
Admin: System-CSV-Templates (csv_field_mappings, is_system=true) pflegen (Issue #21).
"""
from __future__ import annotations

from typing import Any, List, Optional

from fastapi import APIRouter, Depends, File, Form, HTTPException, UploadFile
from pydantic import BaseModel, Field
from psycopg2.extras import Json

from auth import require_admin
from db import get_db, get_cursor, r2d
from csv_parser.core import (
    column_signature,
    decode_raw_bytes,
    get_csv_import_limits,
    headers_signature_rank_metrics,
    normalize_header_for_signature,
    parse_csv_sample,
)
from csv_parser.mapping_suggest import build_type_conversions_for_mapping, suggest_field_mappings
from csv_parser.module_registry import (
    get_module_definition,
    validate_field_mappings,
    validate_required_field_targets,
)

router = APIRouter(prefix="/api/admin/csv-templates", tags=["admin", "csv-import"])


class CsvSystemTemplateCreate(BaseModel):
    module: str
    mapping_name: str = Field(..., min_length=1, max_length=100)
    description: Optional[str] = None
    column_signature: List[str] = Field(default_factory=list)
    delimiter: str = ","
    encoding: str = "utf-8"
    has_header: bool = True
    field_mappings: dict = Field(default_factory=dict)
    type_conversions: Optional[dict] = None


class CsvSystemTemplateUpdate(BaseModel):
    mapping_name: Optional[str] = Field(default=None, min_length=1, max_length=100)
    description: Optional[str] = None
    column_signature: Optional[List[str]] = None
    delimiter: Optional[str] = None
    encoding: Optional[str] = None
    has_header: Optional[bool] = None
    field_mappings: Optional[dict] = None
    type_conversions: Optional[dict] = None


class CsvImportLimitsBody(BaseModel):
    max_rows_per_file: int = Field(..., ge=100, le=2_000_000)
    max_file_bytes: int = Field(..., ge=10_000, le=2_147_483_648)


def _row_full(m: dict) -> dict:
    return {
        "id": m["id"],
        "module": m["module"],
        "mapping_name": m["mapping_name"],
        "description": m.get("description"),
        "column_signature": list(m["column_signature"]) if m.get("column_signature") else [],
        "delimiter": m["delimiter"],
        "encoding": m["encoding"],
        "has_header": m["has_header"],
        "field_mappings": m["field_mappings"],
        "type_conversions": m.get("type_conversions"),
        "usage_count": m.get("usage_count"),
        "success_rate": m.get("success_rate"),
        "last_used_at": m.get("last_used_at"),
        "created_at": m.get("created_at"),
        "updated_at": m.get("updated_at"),
        "is_system": m["is_system"],
    }


@router.get("/import-limits")
def admin_get_csv_import_limits(session: dict = Depends(require_admin)):
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute("SELECT value FROM system_config WHERE key = %s", ("csv_import",))
        row = cur.fetchone()
    return get_csv_import_limits(r2d(row) if row else None)


@router.put("/import-limits")
def admin_put_csv_import_limits(body: CsvImportLimitsBody, session: dict = Depends(require_admin)):
    payload = {"max_rows_per_file": body.max_rows_per_file, "max_file_bytes": body.max_file_bytes}
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute(
            """
            INSERT INTO system_config (key, value, updated_at)
            VALUES ('csv_import', %s, CURRENT_TIMESTAMP)
            ON CONFLICT (key) DO UPDATE
            SET value = EXCLUDED.value, updated_at = CURRENT_TIMESTAMP
            """,
            (Json(payload),),
        )
    return payload


@router.get("")
def list_system_templates(
    module: Optional[str] = None,
    session: dict = Depends(require_admin),
):
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute(
            """
            SELECT * FROM csv_field_mappings
            WHERE is_system = true AND profile_id IS NULL
              AND (%s::text IS NULL OR module = %s)
            ORDER BY module, mapping_name
            """,
            (module, module),
        )
        rows = [r2d(r) for r in cur.fetchall()]
    return {"templates": [_row_full(m) for m in rows]}


@router.post("/analyze-upload")
async def admin_analyze_csv_for_template(
    file: UploadFile = File(...),
    module: str = Form(...),
    delimiter: Optional[str] = Form(default=None),
    seed_template_id: Optional[int] = Form(default=None),
    session: dict = Depends(require_admin),
):
    """
    CSV hochladen wie im Nutzer-Import: Spalten + Vorschau + Vorschläge für field_mappings
    und type_conversions. Optional Seed-Vorlage (ID) oder beste Systemvorlage (Abdeckung, dann Jaccard).
    """
    _ = session
    if not get_module_definition(module):
        raise HTTPException(400, f"Unbekanntes Modul: {module}")

    raw = await file.read()
    limits = _admin_csv_limits()
    max_bytes = limits.get("max_file_bytes", 52_428_800)
    if len(raw) > max_bytes:
        raise HTTPException(
            413,
            f"Datei zu groß (max. {max_bytes} Bytes laut Systemkonfiguration)",
        )

    text = decode_raw_bytes(raw)
    if not text.strip():
        raise HTTPException(400, "Leere Datei")

    max_rows = limits.get("max_rows_per_file", 50_000)
    if text.count("\n") > max_rows + 5:
        raise HTTPException(
            413,
            f"Zu viele Zeilen (>{max_rows}) laut Systemkonfiguration",
        )

    delim = delimiter if delimiter in (",", ";", "\t") else None
    headers, sample_rows, used_delim = parse_csv_sample(text, delimiter=delim, max_data_rows=5)
    if not headers:
        raise HTTPException(400, "Keine Kopfzeile oder leeres CSV")

    sig = column_signature(headers)

    seed_row: dict | None = None
    with get_db() as conn:
        cur = get_cursor(conn)
        if seed_template_id is not None:
            cur.execute(
                """
                SELECT * FROM csv_field_mappings
                WHERE id = %s AND is_system = true AND profile_id IS NULL AND module = %s
                """,
                (seed_template_id, module),
            )
            seed_row = r2d(cur.fetchone())
            if not seed_row:
                raise HTTPException(404, "Seed-Vorlage nicht gefunden oder falsches Modul")
        else:
            cur.execute(
                """
                SELECT * FROM csv_field_mappings
                WHERE is_system = true AND profile_id IS NULL AND module = %s
                """,
                (module,),
            )
            rows = [r2d(r) for r in cur.fetchall()]
            best: dict | None = None
            best_key: tuple[float, int, float] = (-1.0, -1, -1.0)
            for t in rows:
                t_sig = list(t.get("column_signature") or [])
                m = headers_signature_rank_metrics(sig, t_sig)
                key = (m["confidence"], m["columns_matched"], m["jaccard"])
                if key > best_key:
                    best_key = key
                    best = t
            if best and best_key[0] > 0:
                seed_row = best

    seed_fm = (seed_row or {}).get("field_mappings") or {}
    if isinstance(seed_fm, str):
        seed_fm = {}
    seed_tc = (seed_row or {}).get("type_conversions")
    if not isinstance(seed_tc, dict):
        seed_tc = {}

    field_mappings = suggest_field_mappings(headers, module, seed_fm if seed_fm else None)
    type_conversions = build_type_conversions_for_mapping(module, field_mappings, seed_tc if seed_tc else None)

    seed_meta = None
    if seed_row:
        t_sig = list(seed_row.get("column_signature") or [])
        sm = headers_signature_rank_metrics(sig, t_sig)
        seed_meta = {
            "id": seed_row["id"],
            "mapping_name": seed_row.get("mapping_name"),
            "confidence": sm["confidence"],
            "template_recall": sm["template_recall"],
            "jaccard": sm["jaccard"],
            "columns_matched": sm["columns_matched"],
            "columns_in_template": sm["columns_in_template"],
            "columns_in_csv": sm["columns_in_csv"],
        }

    return {
        "filename": file.filename,
        "module": module,
        "delimiter": used_delim,
        "encoding": "utf-8",
        "columns": headers,
        "column_signature_normalized": sig,
        "sample_rows": sample_rows,
        "seed_template": seed_meta,
        "field_mappings": field_mappings,
        "type_conversions": type_conversions,
    }


def _admin_csv_limits() -> dict[str, int]:
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute("SELECT value FROM system_config WHERE key = %s", ("csv_import",))
        row = cur.fetchone()
    return get_csv_import_limits(r2d(row) if row else None)


@router.get("/{template_id}")
def get_system_template(template_id: int, session: dict = Depends(require_admin)):
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute(
            "SELECT * FROM csv_field_mappings WHERE id = %s AND is_system = true AND profile_id IS NULL",
            (template_id,),
        )
        m = r2d(cur.fetchone())
    if not m:
        raise HTTPException(404, "System-Template nicht gefunden")
    return _row_full(m)


@router.post("")
def create_system_template(body: CsvSystemTemplateCreate, session: dict = Depends(require_admin)):
    if not get_module_definition(body.module):
        raise HTTPException(400, f"Unbekanntes Modul: {body.module}")
    try:
        validate_field_mappings(body.module, body.field_mappings)
        validate_required_field_targets(body.module, body.field_mappings)
    except ValueError as e:
        raise HTTPException(400, str(e))

    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute(
            """
            INSERT INTO csv_field_mappings (
                profile_id, is_system, module, mapping_name, description,
                column_signature, delimiter, encoding, has_header,
                field_mappings, type_conversions
            ) VALUES (
                NULL, true, %s, %s, %s, %s, %s, %s, %s, %s, %s
            ) RETURNING id
            """,
            (
                body.module,
                body.mapping_name,
                body.description,
                body.column_signature,
                body.delimiter,
                body.encoding,
                body.has_header,
                Json(body.field_mappings),
                Json(body.type_conversions) if body.type_conversions is not None else None,
            ),
        )
        new_id = cur.fetchone()["id"]
    return {"id": new_id}


@router.put("/{template_id}")
def update_system_template(
    template_id: int,
    body: CsvSystemTemplateUpdate,
    session: dict = Depends(require_admin),
):
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute(
            "SELECT * FROM csv_field_mappings WHERE id = %s AND is_system = true AND profile_id IS NULL",
            (template_id,),
        )
        existing = r2d(cur.fetchone())
        if not existing:
            raise HTTPException(404, "System-Template nicht gefunden")

        patch: dict[str, Any] = body.model_dump(exclude_unset=True)
        if not patch:
            return _row_full(existing)

        fm = patch.get("field_mappings", existing["field_mappings"])
        if "field_mappings" in patch:
            try:
                validate_field_mappings(existing["module"], fm)
                validate_required_field_targets(existing["module"], fm)
            except ValueError as e:
                raise HTTPException(400, str(e))

        fields_sql = []
        vals: list = []
        if "mapping_name" in patch:
            fields_sql.append("mapping_name = %s")
            vals.append(patch["mapping_name"])
        if "description" in patch:
            fields_sql.append("description = %s")
            vals.append(patch["description"])
        if "column_signature" in patch:
            fields_sql.append("column_signature = %s")
            vals.append(patch["column_signature"])
        if "delimiter" in patch:
            fields_sql.append("delimiter = %s")
            vals.append(patch["delimiter"])
        if "encoding" in patch:
            fields_sql.append("encoding = %s")
            vals.append(patch["encoding"])
        if "has_header" in patch:
            fields_sql.append("has_header = %s")
            vals.append(patch["has_header"])
        if "field_mappings" in patch:
            fields_sql.append("field_mappings = %s")
            vals.append(Json(patch["field_mappings"]))
        if "type_conversions" in patch:
            fields_sql.append("type_conversions = %s")
            tc = patch["type_conversions"]
            vals.append(Json(tc) if tc is not None else None)

        fields_sql.append("updated_at = CURRENT_TIMESTAMP")
        vals.append(template_id)

        cur.execute(
            f"UPDATE csv_field_mappings SET {', '.join(fields_sql)} WHERE id = %s",
            tuple(vals),
        )

        cur.execute("SELECT * FROM csv_field_mappings WHERE id = %s", (template_id,))
        m = r2d(cur.fetchone())
    return _row_full(m)


@router.delete("/{template_id}")
def delete_system_template(template_id: int, session: dict = Depends(require_admin)):
    with get_db() as conn:
        cur = get_cursor(conn)
        cur.execute(
            "DELETE FROM csv_field_mappings WHERE id = %s AND is_system = true AND profile_id IS NULL RETURNING id",
            (template_id,),
        )
        row = cur.fetchone()
        if not row:
            raise HTTPException(404, "System-Template nicht gefunden")
    return {"deleted": template_id}