import type { Sign } from './constants.js';

/** The ephemeris that actually produced a result. */
export type EphemerisModel = 'swiss' | 'moshier' | 'jpl';

/** A body's position. */
export interface Position {
  /** Ecliptic longitude in degrees, [0, 360). Right ascension under `Flag.Equatorial`. */
  longitude: number;
  /** Ecliptic latitude in degrees. Declination under `Flag.Equatorial`. */
  latitude: number;
  /** Distance in astronomical units. */
  distance: number;
  /** Change in longitude, degrees per day. Negative means retrograde. */
  longitudeSpeed: number;
  latitudeSpeed: number;
  /** Change in distance, AU per day. */
  distanceSpeed: number;

  /**
   * Which ephemeris was actually used.
   *
   * Swiss Ephemeris does **not** fail when it cannot find the `.se1` file you
   * asked for — it falls back to Moshier without saying so. Check this field
   * or you will believe you have a precision you did not get.
   */
  ephemeris: EphemerisModel;

  /** Warning text from the library, e.g. a missing file. Null when clean. */
  warning: string | null;
}

/** A position with sign and retrograde state derived. */
export interface PositionWithSign extends Position {
  /** Sign index, 0 = Aries. */
  signIndex: number;
  sign: Sign;
  /** Degrees within the sign, [0, 30). */
  degreeInSign: number;
  /** True when longitude speed is negative. */
  retrograde: boolean;
}

/** Equatorial coordinates — what declination work needs. */
export interface EquatorialPosition {
  /** Right ascension in degrees, [0, 360). */
  rightAscension: number;
  /** Declination in degrees, north positive. */
  declination: number;
  distance: number;
  /** Degrees per day. */
  rightAscensionSpeed: number;
  /** Degrees per day. Drives applying/separating for parallels. */
  declinationSpeed: number;
  distanceSpeed: number;
  ephemeris: EphemerisModel;
  warning: string | null;
}

/** Obliquity of the ecliptic and the nutation at a moment. */
export interface Obliquity {
  /** True obliquity — mean plus the nutation in obliquity. */
  trueObliquity: number;
  meanObliquity: number;
  nutationInLongitude: number;
  nutationInObliquity: number;
}

/** An observer's place on Earth. */
export interface GeoPosition {
  /** Geographic latitude, north positive. */
  latitude: number;
  /** Geographic longitude, east positive. */
  longitude: number;
  /** Height above sea level in metres. Defaults to 0. */
  altitude?: number;
}

/** House cusps and angles. */
export interface Houses {
  /**
   * The cusps, `cusps[0]` being the first house. (The C API uses a 1-based
   * array; this one is 0-based.)
   *
   * **Twelve entries for every house system except `'G'`.** Gauquelin sectors
   * are 36, and they are counted in the *clockwise* direction — check
   * `cusps.length` rather than assuming twelve. The one exception is a
   * Gauquelin chart beyond the polar circle: the system is undefined there,
   * Swiss Ephemeris substitutes Porphyry and produces only twelve cusps, so
   * `substituted` is true and `cusps.length` is 12.
   */
  cusps: number[];

  /** The house system code that was asked for. */
  requestedSystem: string;

  /**
   * True when Swiss Ephemeris used a different system than the one requested.
   *
   * Placidus, Koch, Gauquelin and Sunshine are mathematically undefined
   * beyond the polar circle. Swiss Ephemeris quietly substitutes Porphyry and
   * returns −1 (swehouse.c:1252) while still filling in **valid** cusps — so
   * that −1 is a warning, not a failure.
   *
   * Ignore this field and a high-latitude chart may be using a house system
   * you did not choose. The `warning` text names the substitute.
   */
  substituted: boolean;
  ascendant: number;
  midheaven: number;
  /**
   * The Descendant — the Ascendant's opposition.
   *
   * Derived here rather than read from a cusp on purpose. In a quadrant
   * system it equals `cusps[6]`, but in whole sign, equal, Morinus, Vehlow
   * and the meridian systems it does **not**: the seventh cusp is a house
   * boundary, and the Descendant is where the ecliptic meets the western
   * horizon. Reading one for the other is wrong by up to a whole sign.
   */
  descendant: number;
  /**
   * The Imum Coeli — the Midheaven's opposition, the lower meridian.
   * Equal to `cusps[3]` in a quadrant system and not otherwise; see
   * {@link descendant}.
   */
  imumCoeli: number;
  /** Right ascension of the meridian. */
  armc: number;
  vertex: number;
  equatorialAscendant: number;
  coAscendantKoch: number;
  coAscendantMunkasey: number;
  polarAscendant: number;
  warning: string | null;
}

/** A fixed star's position. */
export interface StarPosition extends Position {
  /**
   * The full name the library resolved, in the form `Aldebaran,alTau`:
   * traditional name plus Bayer/Flamsteed designation.
   */
  resolvedName: string;
}

/** A Julian day converted back to a calendar date. */
export interface CalendarDate {
  year: number;
  month: number;
  day: number;
  /** Decimal hour, e.g. 14.5 = 14:30. */
  hour: number;
}

export interface CalcOptions {
  /**
   * Extra flags (`Flag.*`). The ephemeris source and `Flag.Speed` are added
   * by default; both can be overridden from here.
   */
  flags?: number;
  /** Ephemeris source. Defaults to `'swiss'`, which falls back to Moshier. */
  ephemeris?: EphemerisModel;
}

export interface SwissEphOptions {
  /**
   * Ephemeris files to write into the virtual filesystem. Keys are file names
   * (`"sepl_18.se1"`), values are the contents.
   */
  files?: Record<string, Uint8Array | ArrayBuffer>;
  /**
   * Where to look for ephemeris files. A real directory under Node; the
   * virtual directory populated by `files` in a browser (default `/ephe`).
   */
  ephemerisPath?: string;
}

/** Thrown when Swiss Ephemeris reports an error. */
export class SwissEphError extends Error {
  constructor(
    message: string,
    /** The C function that failed. */
    public readonly fn: string,
    /**
     * The library's own `serr` text, when `message` rephrases it.
     *
     * Kept because it is the ground truth and because a Swiss Ephemeris user
     * may recognise it — but it is not the message, since it can point
     * somewhere unhelpful. A missing-file error names the **virtual** search
     * path inside the WebAssembly filesystem (`'.:/users/ephe/'`), which does
     * not exist on the caller's machine and sends them looking in the wrong
     * place.
     */
    public readonly detail?: string,
  ) {
    super(message);
    this.name = 'SwissEphError';
  }

  /**
   * The `.se1` file the library could not find, when that is what failed.
   *
   * Null for every other error. Useful for deciding what to fetch and retry.
   */
  get missingFile(): string | null {
    const source = this.detail ?? this.message;
    return /SwissEph file '([^']+)' not found/.exec(source)?.[1] ?? null;
  }
}