/**
 * Canonical source of truth for US states and their Seahaven area zone
 * mapping. Exactly the 50 states — no DC and no territories.
 * Area is always derived from the state code and never persisted.
 */
export const AREA_ZONES = ["East", "Central", "West", "California"] as const;

export type AreaZone = (typeof AREA_ZONES)[number];

export const AREA_ZONE_STATE_CODES = {
  East: [
    "CT",
    "DE",
    "GA",
    "MA",
    "MD",
    "ME",
    "NC",
    "NH",
    "NJ",
    "NY",
    "PA",
    "RI",
    "SC",
    "VA",
    "VT",
    "WV",
  ],
  Central: [
    "AL",
    "AR",
    "FL",
    "IA",
    "IL",
    "IN",
    "KS",
    "KY",
    "LA",
    "MI",
    "MN",
    "MO",
    "MS",
    "ND",
    "NE",
    "OH",
    "OK",
    "SD",
    "TN",
    "WI",
  ],
  West: ["AK", "AZ", "CO", "HI", "ID", "MT", "NM", "NV", "OR", "TX", "UT", "WA", "WY"],
  California: ["CA"],
} as const satisfies Record<AreaZone, readonly string[]>;

export type StateCode = (typeof AREA_ZONE_STATE_CODES)[AreaZone][number];

/** All 50 state codes in canonical order: East, Central, West, California. */
export const US_STATE_CODES = [
  ...AREA_ZONE_STATE_CODES.East,
  ...AREA_ZONE_STATE_CODES.Central,
  ...AREA_ZONE_STATE_CODES.West,
  ...AREA_ZONE_STATE_CODES.California,
] as [StateCode, ...StateCode[]];

const STATE_NAMES = {
  AL: "Alabama",
  AK: "Alaska",
  AZ: "Arizona",
  AR: "Arkansas",
  CA: "California",
  CO: "Colorado",
  CT: "Connecticut",
  DE: "Delaware",
  FL: "Florida",
  GA: "Georgia",
  HI: "Hawaii",
  ID: "Idaho",
  IL: "Illinois",
  IN: "Indiana",
  IA: "Iowa",
  KS: "Kansas",
  KY: "Kentucky",
  LA: "Louisiana",
  ME: "Maine",
  MD: "Maryland",
  MA: "Massachusetts",
  MI: "Michigan",
  MN: "Minnesota",
  MS: "Mississippi",
  MO: "Missouri",
  MT: "Montana",
  NE: "Nebraska",
  NV: "Nevada",
  NH: "New Hampshire",
  NJ: "New Jersey",
  NM: "New Mexico",
  NY: "New York",
  NC: "North Carolina",
  ND: "North Dakota",
  OH: "Ohio",
  OK: "Oklahoma",
  OR: "Oregon",
  PA: "Pennsylvania",
  RI: "Rhode Island",
  SC: "South Carolina",
  SD: "South Dakota",
  TN: "Tennessee",
  TX: "Texas",
  UT: "Utah",
  VT: "Vermont",
  VA: "Virginia",
  WA: "Washington",
  WV: "West Virginia",
  WI: "Wisconsin",
  WY: "Wyoming",
} as const satisfies Record<StateCode, string>;

export interface StateAreaEntry {
  code: StateCode;
  name: string;
  zone: AreaZone;
}

/** All 50 states with postal code, full name, and their single area zone. */
export const STATE_AREA_ENTRIES: readonly StateAreaEntry[] = AREA_ZONES.flatMap((zone) =>
  AREA_ZONE_STATE_CODES[zone].map((code) => ({ code, name: STATE_NAMES[code], zone })),
);

const STATE_CODE_SET = new Set<string>(US_STATE_CODES);

const STATE_NAME_TO_CODE = new Map<string, StateCode>(
  STATE_AREA_ENTRIES.map((entry) => [entry.name.toLowerCase(), entry.code]),
);

const STATE_ZONE_BY_CODE = Object.fromEntries(
  STATE_AREA_ENTRIES.map((entry) => [entry.code, entry.zone]),
) as Record<StateCode, AreaZone>;

/** Autocomplete option label: `Texas (TX)`. */
export function formatStateOptionLabel(code: StateCode): string {
  return `${STATE_NAMES[code]} (${code})`;
}

/**
 * Normalizes legacy API state values to the canonical two-letter code.
 * Accepts codes in any case and full state names (any case); otherwise null.
 */
export function normalizeStateCode(value: string | null | undefined): StateCode | null {
  const trimmed = value?.trim() ?? "";
  if (trimmed === "") {
    return null;
  }
  const upper = trimmed.toUpperCase();
  if (STATE_CODE_SET.has(upper)) {
    return upper as StateCode;
  }
  return STATE_NAME_TO_CODE.get(trimmed.toLowerCase()) ?? null;
}

/** Derives the area zone for a state code or legacy full-name value. */
export function getAreaForState(value: string | null | undefined): AreaZone | null {
  const code = normalizeStateCode(value);
  return code === null ? null : STATE_ZONE_BY_CODE[code];
}

/** Expands selected area zones to their state codes in canonical order. */
export function expandAreasToStateCodes(areas: readonly AreaZone[]): StateCode[] {
  const selected = new Set<AreaZone>(areas);
  return US_STATE_CODES.filter((code) => selected.has(STATE_ZONE_BY_CODE[code]));
}