"""CSV source parser – reads SMB/NFS share definitions from customer-supplied CSV files."""
from __future__ import annotations

import csv
import sys
from pathlib import Path
from typing import Any

from .colors import log


# ─────────────────────────────────────────────────────────────────────────────
# Column type metadata
# ─────────────────────────────────────────────────────────────────────────────

# Columns coerced to bool
_SMB_BOOL_COLS = frozenset({"ro", "browsable", "guestok", "abe", "timemachine", "enabled"})
# Columns coerced to list[str] (space-or-comma-separated in CSV)
_SMB_LIST_COLS = frozenset({"hostsallow", "hostsdeny"})
_SMB_REQUIRED  = frozenset({"name", "path"})

_NFS_BOOL_COLS = frozenset({"ro", "enabled"})
_NFS_LIST_COLS = frozenset({"security", "hosts", "networks"})
_NFS_REQUIRED  = frozenset({"path"})


# ─────────────────────────────────────────────────────────────────────────────
# Internal helpers
# ─────────────────────────────────────────────────────────────────────────────

def _parse_bool(value: str, col: str, row_num: int) -> bool:
    v = value.strip().lower()
    if v in ("true", "yes", "1"):
        return True
    if v in ("false", "no", "0", ""):
        return False
    log.warning("  row %d: unrecognised boolean %r for column %r – treating as False",
                row_num, value, col)
    return False


def _parse_list(value: str) -> list[str]:
    """Split space-or-comma-separated value into a list, dropping blanks."""
    return [p for p in value.replace(",", " ").split() if p]


def _coerce_row(
    row: dict[str, str],
    bool_cols: frozenset[str],
    list_cols: frozenset[str],
    required: frozenset[str],
    row_num: int,
) -> dict[str, Any] | None:
    """Validate and type-coerce one CSV row.  Returns None to skip the row."""
    if not any((v or "").strip() for v in row.values()):
        return None  # blank row

    first_val = next(iter(row.values()), "") or ""
    if first_val.strip().startswith("#"):
        return None  # comment row

    result: dict[str, Any] = {}
    for col, raw in row.items():
        if col is None:
            continue
        col = col.strip()
        val = (raw or "").strip()

        if not val:
            continue  # omit empty optional fields; API uses its defaults

        if col in bool_cols:
            result[col] = _parse_bool(val, col, row_num)
        elif col in list_cols:
            result[col] = _parse_list(val)
        else:
            result[col] = val

    for req in required:
        if req not in result:
            log.warning("  row %d: missing required field %r – skipping row", row_num, req)
            return None

    return result


def _parse_csv(
    csv_path: str,
    bool_cols: frozenset[str],
    list_cols: frozenset[str],
    required: frozenset[str],
    label: str,
) -> list[dict]:
    path = Path(csv_path)
    if not path.is_file():
        log.error("%s CSV file not found: %s", label, csv_path)
        sys.exit(1)

    shares: list[dict] = []
    try:
        with path.open(newline="", encoding="utf-8-sig") as fh:
            reader = csv.DictReader(fh)
            if reader.fieldnames is None:
                log.error("%s CSV has no header row: %s", label, csv_path)
                sys.exit(1)

            header = {c.strip() for c in reader.fieldnames if c is not None}
            missing_req = required - header
            if missing_req:
                log.error(
                    "%s CSV is missing required column(s): %s",
                    label, ", ".join(sorted(missing_req)),
                )
                sys.exit(1)

            for row_num, row in enumerate(reader, start=2):
                normalised = {(k or "").strip(): v for k, v in row.items()}
                share = _coerce_row(normalised, bool_cols, list_cols, required, row_num)
                if share is not None:
                    shares.append(share)

    except OSError as exc:
        log.error("Cannot read %s CSV: %s", label, exc)
        sys.exit(1)

    log.info("  %-14s  →  %s (%d share(s))", label.lower() + "_shares", csv_path, len(shares))
    return shares


# ─────────────────────────────────────────────────────────────────────────────
# Public API
# ─────────────────────────────────────────────────────────────────────────────

def parse_smb_csv(csv_path: str) -> list[dict]:
    """Parse an SMB shares CSV.  Returns share dicts compatible with migrate.py."""
    return _parse_csv(csv_path, _SMB_BOOL_COLS, _SMB_LIST_COLS, _SMB_REQUIRED, "SMB")


def parse_nfs_csv(csv_path: str) -> list[dict]:
    """Parse an NFS shares CSV.  Returns share dicts compatible with migrate.py."""
    return _parse_csv(csv_path, _NFS_BOOL_COLS, _NFS_LIST_COLS, _NFS_REQUIRED, "NFS")


def parse_csv_sources(smb_csv: str | None, nfs_csv: str | None) -> dict[str, Any]:
    """
    Parse one or both CSV files.
    Returns {"smb_shares": list, "nfs_shares": list} — same shape as parse_archive().
    """
    log.info("Loading shares from CSV source(s).")
    result: dict[str, Any] = {"smb_shares": [], "nfs_shares": []}
    if smb_csv:
        result["smb_shares"] = parse_smb_csv(smb_csv)
    if nfs_csv:
        result["nfs_shares"] = parse_nfs_csv(nfs_csv)
    log.info(
        "Loaded: %d SMB share(s), %d NFS share(s)",
        len(result["smb_shares"]),
        len(result["nfs_shares"]),
    )
    return result