export const ELL = 0;
export const MSL = 1;
export const GND = 2;

export const heightMode: Record<string, number> = {
    ell: ELL,
    msl: MSL,
    gnd: GND
};

const KM_to_M = 1000.0;
const M_to_KM = 1.0 / KM_to_M;
const FT_to_M = 0.3048;
const M_to_FT = 1.0 / FT_to_M;
const MS_to_KMH = 3.6;
const KMH_to_MS = 1.0 / MS_to_KMH;
const MS_to_FTS = 3.28084;
const FT_to_KM = FT_to_M * M_to_KM;
const KM_to_FT = 1.0 / FT_to_KM;

export const m = 0;
export const km = 1;
export const ft = 2;
export const s = 3;
export const h = 4;
export const ms = 5;
export const kmh = 6;
export const fts = 7;

const DEFAULT_NAN = "--";

const _abbr: string[] = ["m", "km", "ft", "s", "h", "m/s", "km/h", "ft/s"];

export const _tenth = [0, 2, 0, 0, 0, 0, 0, 0];

let _convFn: ((v: number) => number)[][] = [];

_convFn[m] = [];
_convFn[m][m] = (v: number): number => v;
_convFn[m][km] = (v: number): number => v * M_to_KM;
_convFn[m][ft] = (v: number): number => v * M_to_FT;

_convFn[ft] = [];
_convFn[ft][m] = (v: number): number => v * FT_to_M;
_convFn[ft][km] = (v: number): number => v * FT_to_KM;
_convFn[ft][ft] = (v: number): number => v;

_convFn[km] = [];
_convFn[km][m] = (v: number): number => v * KM_to_M;
_convFn[km][km] = (v: number): number => v;
_convFn[km][ft] = (v: number): number => v * KM_to_FT;

_convFn[ms] = [];
_convFn[ms][ms] = (v: number): number => v;
_convFn[ms][kmh] = (v: number): number => v * MS_to_KMH;
_convFn[ms][fts] = (v: number): number => v * MS_to_FTS;

_convFn[kmh] = [];
_convFn[kmh][ms] = (v: number): number => v * KMH_to_MS;
_convFn[kmh][kmh] = (v: number): number => v;

//_convFn[kmh][fts] = (v) => v * KMH_to_FTS;

export function convert(from: number, to: number, val: number): number {
    return _convFn[from][to](val);
}

export function convertExt(isNotNaN: boolean, unitFrom: number, unitTo: number, val: number, fixed?: number): string {
    if (isNotNaN) {
        return convert(unitFrom, unitTo, val).toFixed(fixed || _tenth[unitTo]);
    }
    return DEFAULT_NAN;
}

export function toString(u: number) {
    return _abbr[u];
}