"""
import_drivers_csv.py — Fireside Communications · Driver & Vehicle CSV Import
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One-shot script: reads the snake_case Fireside Group vehicle CSV
(`20260427_FSG_Vehicles_mitieng.csv`), compares each row against the
current `tracksolid.devices` values, and updates the DB.

The CSV columns mirror the DB schema directly — no inference. Cells with the
literal string "NULL" are treated as missing.

Fields imported (per Phase 0.1 of the Business Analytics redesign plan):
    Identity        : driver_name, driver_phone, vehicle_number, vehicle_name,
                      vehicle_models, mc_type, device_name
    SIM             : sim, iccid, imsi
    Lifecycle       : activation_time, expiration
    Business meta   : assigned_city, cost_centre, assigned_route,
                      vehicle_category, vehicle_brand, fuel_100km, depot_address

`depot_geom` (PostGIS Point) is intentionally NOT imported — needs WKT and
isn't present as coordinates in the CSV. Set it via a follow-up migration
when geofences are loaded.

Usage:
    # Dry-run — shows diff, writes nothing
    python import_drivers_csv.py

    # Filter to a single IMEI (dry-run)
    python import_drivers_csv.py --imei 862798052707896

    # Apply all changes to DB
    python import_drivers_csv.py --apply

    # Only fill fields that are currently NULL in the DB (never overwrite)
    python import_drivers_csv.py --only-null --apply

    # Use a different CSV
    python import_drivers_csv.py --csv path/to/file.csv

Pre-requisite:
    Migrations 02, 05, 06 must be applied (they add the metadata columns).
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"""

import argparse
import csv
from pathlib import Path

from ts_shared_rev import clean, clean_num, clean_ts, get_conn, get_logger

log = get_logger("csv_import")

DEFAULT_CSV_PATH = Path(__file__).parent / "20260427_FSG_Vehicles_mitieng.csv"

# Columns fetched from DB for diff comparison.
DB_COLS = [
    "imei",
    # Identity
    "driver_name", "driver_phone", "vehicle_number", "vehicle_name",
    "vehicle_models", "mc_type", "device_name",
    # SIM
    "sim", "iccid", "imsi",
    # Lifecycle
    "activation_time", "expiration",
    # Business metadata (Phase 0.1 additions)
    "assigned_city", "cost_centre", "assigned_route",
    "vehicle_category", "vehicle_brand", "fuel_100km", "depot_address",
]

# Driver Name values that are placeholders — skip writing driver_name for these.
_DRIVER_SKIP = {"identification", "ug"}

# Columns that need an explicit cast in the UPDATE statement.
_TIMESTAMPTZ_COLS = {"activation_time", "expiration"}
_NUMERIC_COLS = {"fuel_100km"}


def _read(row: dict, col: str) -> str | None:
    """Read a CSV column treating literal 'NULL'/'None' (case-insensitive) as missing."""
    v = clean(row.get(col))
    if v is None:
        return None
    return None if v.upper() in ("NULL", "NONE") else v


def _read_num(row: dict, col: str) -> float | None:
    v = _read(row, col)
    return clean_num(v) if v is not None else None


def _read_ts(row: dict, col: str) -> str | None:
    v = _read(row, col)
    return clean_ts(v) if v is not None else None


def load_csv(csv_path: Path) -> dict[str, dict]:
    """Load CSV into a dict keyed by IMEI."""
    rows: dict[str, dict] = {}
    with open(csv_path, encoding="utf-8-sig", newline="") as f:
        for row in csv.DictReader(f):
            imei = (row.get("imei") or "").strip()
            if not imei:
                continue
            rows[imei] = row
    log.info("CSV loaded: %d rows from %s", len(rows), csv_path.name)
    return rows


def load_db_devices() -> dict[str, dict]:
    """Fetch current device rows from DB, keyed by IMEI."""
    devices: dict[str, dict] = {}
    with get_conn() as conn:
        with conn.cursor() as cur:
            cur.execute(f"SELECT {', '.join(DB_COLS)} FROM tracksolid.devices")
            col_names = [d[0] for d in cur.description]
            for row in cur.fetchall():
                rec = dict(zip(col_names, row))
                devices[rec["imei"]] = rec
    log.info("DB loaded: %d devices", len(devices))
    return devices


def build_update(csv_row: dict, db_row: dict | None, only_null: bool) -> dict[str, object]:
    """
    Return a dict of column→new_value for fields that need updating.
    When only_null=True, skip any DB column that already has a value.
    The driver_name column is skipped for placeholder-labelled devices.
    """
    driver_raw = (_read(csv_row, "driver_name") or "")
    is_placeholder = driver_raw.lower() in _DRIVER_SKIP
    if driver_raw.lower() == "identification":
        return {}

    proposed: dict[str, object] = {
        # Identity
        "driver_phone":     _read(csv_row, "driver_phone"),
        "vehicle_number":   _read(csv_row, "vehicle_number"),
        "vehicle_name":     _read(csv_row, "vehicle_name"),
        "vehicle_models":   _read(csv_row, "vehicle_models"),
        "mc_type":          _read(csv_row, "mc_type"),
        "device_name":      _read(csv_row, "device_name"),
        # SIM
        "sim":              _read(csv_row, "sim"),
        "iccid":            _read(csv_row, "iccid"),
        "imsi":             _read(csv_row, "imsi"),
        # Lifecycle
        "activation_time":  _read_ts(csv_row, "activation_time"),
        "expiration":       _read_ts(csv_row, "expiration"),
        # Business metadata
        "assigned_city":    _read(csv_row, "assigned_city"),
        "cost_centre":      _read(csv_row, "cost_centre"),
        "assigned_route":   _read(csv_row, "assigned_route"),
        "vehicle_category": _read(csv_row, "vehicle_category"),
        "vehicle_brand":    _read(csv_row, "vehicle_brand"),
        "fuel_100km":       _read_num(csv_row, "fuel_100km"),
        "depot_address":    _read(csv_row, "depot_address"),
    }
    if not is_placeholder and driver_raw:
        proposed["driver_name"] = driver_raw

    # Drop None values — no point sending NULL to overwrite NULL.
    proposed = {k: v for k, v in proposed.items() if v is not None}

    if not only_null or db_row is None:
        return proposed

    # only_null: drop any column that already has a non-null value in the DB.
    return {k: v for k, v in proposed.items() if db_row.get(k) is None}


def print_diff(imei: str, updates: dict[str, object], db_row: dict | None) -> None:
    """Pretty-print what will change for one device."""
    if not updates:
        return
    db = db_row or {}
    print(f"\n  IMEI {imei}:")
    for col, new_val in sorted(updates.items()):
        old_val = db.get(col)
        if str(old_val) != str(new_val):
            print(f"    {col:<20} {str(old_val):<30} → {new_val}")


def _set_clause(col: str) -> str:
    """SQL fragment for `col = ...` honouring per-column casts."""
    if col in _TIMESTAMPTZ_COLS:
        return f"{col} = COALESCE(%s::TIMESTAMPTZ, {col})"
    if col in _NUMERIC_COLS:
        # %s already a float; no NULLIF dance needed.
        return f"{col} = COALESCE(%s::NUMERIC, {col})"
    return f"{col} = COALESCE(NULLIF(%s, ''), {col})"


def _placeholder(col: str) -> str:
    """SQL fragment for a single VALUES placeholder honouring per-column casts."""
    if col in _TIMESTAMPTZ_COLS:
        return "%s::TIMESTAMPTZ"
    if col in _NUMERIC_COLS:
        return "%s::NUMERIC"
    return "%s"


def run(apply: bool, only_null: bool, filter_imei: str | None, csv_path: Path) -> None:
    csv_rows = load_csv(csv_path)
    db_rows  = load_db_devices()

    if filter_imei:
        csv_rows = {k: v for k, v in csv_rows.items() if k == filter_imei}
        if not csv_rows:
            print(f"IMEI {filter_imei} not found in CSV.")
            return

    updated = inserted = skipped = no_change = 0

    with get_conn() as conn:
        with conn.cursor() as cur:
            for imei, csv_row in csv_rows.items():
                db_row = db_rows.get(imei)
                updates = build_update(csv_row, db_row, only_null)

                if not updates:
                    driver_raw = (_read(csv_row, "driver_name") or "").lower()
                    if driver_raw == "identification":
                        skipped += 1
                    else:
                        no_change += 1
                    continue

                if db_row is None:
                    # Device not yet synced from API — insert a stub row so
                    # incoming alarms / positions don't trip the FK constraint.
                    print(f"\n  [NEW] IMEI {imei}:")
                    for col, new_val in sorted(updates.items()):
                        print(f"    {col:<20} → {new_val}")
                    if apply:
                        cols = ["imei"] + list(updates.keys())
                        vals = [imei] + list(updates.values())
                        placeholders = ["%s"] + [_placeholder(c) for c in updates.keys()]
                        cur.execute(
                            f"INSERT INTO tracksolid.devices ({', '.join(cols)}) "
                            f"VALUES ({', '.join(placeholders)}) "
                            "ON CONFLICT (imei) DO NOTHING",
                            vals,
                        )
                    inserted += 1
                    continue

                print_diff(imei, updates, db_row)

                if apply:
                    set_clauses = [_set_clause(c) for c in updates.keys()]
                    params = list(updates.values())
                    set_clauses.append("updated_at = NOW()")
                    params.append(imei)
                    cur.execute(
                        f"UPDATE tracksolid.devices SET {', '.join(set_clauses)} WHERE imei = %s",
                        params,
                    )
                    updated += 1
                else:
                    updated += 1  # count as "would update" in dry-run

    mode = "APPLIED" if apply else "DRY-RUN"
    print(f"\n{'='*60}")
    print(f"  {mode} COMPLETE")
    print(f"{'='*60}")
    print(f"  Would update / updated  : {updated}")
    print(f"  Would insert / inserted : {inserted}")
    print(f"  No change needed        : {no_change}")
    print(f"  Skipped (Identification): {skipped}")
    if not apply:
        print("\n  Run with --apply to commit changes.")


if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description="Import driver/vehicle details from CSV into tracksolid.devices"
    )
    parser.add_argument("--apply",     action="store_true", help="Write changes to DB (default: dry-run)")
    parser.add_argument("--only-null", action="store_true", help="Only update fields currently NULL in the DB")
    parser.add_argument("--imei",      default=None,        help="Limit to a single IMEI")
    parser.add_argument("--csv",       default=str(DEFAULT_CSV_PATH),
                        help=f"Path to the CSV (default: {DEFAULT_CSV_PATH.name})")
    args = parser.parse_args()

    csv_path = Path(args.csv)
    if not csv_path.exists():
        log.error("CSV file not found: %s", csv_path)
        raise SystemExit(1)

    run(apply=args.apply, only_null=args.only_null, filter_imei=args.imei, csv_path=csv_path)