/**
 * Shared parsing helpers for the import routes (fuel-logs, plant-hours).
 * Extracted from src/lib/fuel-import-parse.ts so that plant-hours can
 * reuse the column-resolution + date-parsing logic and add a new
 * parseTime helper without duplicating code.
 *
 * All four helpers are stateless and side-effect free. fuel-import-parse
 * re-exports the three legacy helpers so existing consumers keep working.
 */

/** Header aliases for the plant-hours import (13 logical columns). */
export const PLANT_COL_ALIASES: Record<string, string[]> = {
  date_logged:   ["date logged", "date_logged", "date"],
  vehicle_qr:    ["vehicle qr", "vehicle_qr", "qr", "qr_code_id"],
  vehicle_desc:  ["vehicle", "vehicle description", "vehicle_description", "description"],
  start_date:    ["start date", "start_date"],
  end_date:      ["end date", "end_date"],
  start_time:    ["start time", "start_time"],
  end_time:      ["end time", "end_time"],
  start_hours:   ["start hours", "start_hours"],
  end_hours:     ["end hours", "end_hours"],
  hours:         ["hours"],
  notes:         ["notes"],
  hour_meter:    ["hour meter", "hour_meter", "hour_meter_budget", "budget"],
  cost_per_hour: ["cost / hr", "cost/hr", "cost_per_hour", "cost"],
};

/** Header aliases for the fuel-logs import (legacy, kept for the fuel route). */
export const FUEL_COL_ALIASES: Record<string, string[]> = {
  date:          ["date logged", "date_logged", "date"],
  vehicle_qr:    ["vehicle qr", "vehicle_qr", "qr", "qr code id", "qr_code_id"],
  vehicle_desc:  ["vehicle", "vehicle description", "vehicle_description", "description"],
  odo:           ["km's/ hours", "kms/ hours", "km/hours", "odo_reading", "odometer", "hour_meter", "hour meter"],
  litres:        ["litres pumped", "litres", "liters"],
  site:          ["current site", "site", "current_site"],
  consumption:   ["latest consumption", "latest_consumption", "consumption"],
};

/** Normalise a header for fuzzy matching. */
export function normHeader(s: unknown): string {
  return typeof s === "string"
    ? s.replace(/\s+/g, " ").trim().toLowerCase()
    : "";
}

/**
 * Resolve the original header text for a logical column key.
 * Returns the EXACT header string the spreadsheet used (so the row
 * lookup uses the same key the source file provided), or null if no
 * alias matched.
 */
export function resolveColumn(
  headers: string[],
  key: keyof typeof PLANT_COL_ALIASES | keyof typeof FUEL_COL_ALIASES,
  aliasMap: Record<string, string[]> = PLANT_COL_ALIASES as Record<string, string[]>,
): string | null {
  const target = aliasMap[key].map(normHeader);
  for (const h of headers) {
    if (target.includes(normHeader(h))) return h;
  }
  return null;
}

/**
 * Parse the date column into an ISO `YYYY-MM-DD` string.
 * Primary: `DD/MM/YYYY`. Falls back to `YYYY-MM-DD` and Excel serials.
 */
export function parseDate(input: unknown): string | null {
  if (input === null || input === undefined) return null;
  if (typeof input === "number" && Number.isFinite(input) && input > 25569) {
    const d = new Date(Math.round((input - 25569) * 86400 * 1000));
    if (!Number.isNaN(d.getTime())) return d.toISOString().slice(0, 10);
  }
  const s = String(input).trim();
  if (!s) return null;
  let m = /^(\d{1,2})\/(\d{1,2})\/(\d{4})$/.exec(s);
  if (m) {
    const dd = Number(m[1]);
    const mm = Number(m[2]);
    const yyyy = Number(m[3]);
    if (mm >= 1 && mm <= 12 && dd >= 1 && dd <= 31) {
      const iso = new Date(Date.UTC(yyyy, mm - 1, dd));
      if (!Number.isNaN(iso.getTime())) return iso.toISOString().slice(0, 10);
    }
    return null;
  }
  m = /^(\d{4})-(\d{2})-(\d{2})/.exec(s);
  if (m) {
    const iso = new Date(
      Date.UTC(Number(m[1]), Number(m[2]) - 1, Number(m[3])),
    );
    if (!Number.isNaN(iso.getTime())) return iso.toISOString().slice(0, 10);
  }
  return null;
}

/** Coerce a cell value to a finite number, or null if empty / non-numeric. */
export function toNumber(input: unknown): number | null {
  if (input === null || input === undefined) return null;
  if (typeof input === "number") return Number.isFinite(input) ? input : null;
  if (typeof input === "string") {
    const trimmed = input.trim();
    if (!trimmed) return null;
    const n = Number(trimmed);
    return Number.isFinite(n) ? n : null;
  }
  return null;
}

/**
 * Parse a time cell into `HH:MM` (24h). Returns null on malformed input.
 * Single-digit hours are normalised to two digits (`6:00` → `06:00`).
 */
export function parseTime(input: unknown): string | null {
  if (input === null || input === undefined) return null;
  const s = String(input).trim();
  if (!s) return null;
  const m = /^(\d{1,2}):(\d{2})$/.exec(s);
  if (!m) return null;
  const hh = Number(m[1]);
  const mm = Number(m[2]);
  if (hh < 0 || hh > 23 || mm < 0 || mm > 59) return null;
  return `${String(hh).padStart(2, "0")}:${String(mm).padStart(2, "0")}`;
}