import { assertEquals } from "@std/assert";
import { type Chord, chordName, parseChord } from "./chord.ts";
import type { Key, ModeId } from "./key.ts";
import { parseNote } from "./pitch.ts";
import { parallel, relative, suspend, toggleSeventh, tritoneSub } from "./transform.ts";

const key = (tonic = "C", mode: ModeId = "ionian"): Key => ({
  tonic: parseNote(tonic)!.note,
  mode,
});
const C = key();
const apply = (f: (c: Chord) => Chord | undefined, ...symbols: string[]) =>
  symbols.map(s => {
    const out = f(parseChord(s, C)!);
    return out && chordName(out);
  });

Deno.test("parallel swaps the third", () => {
  assertEquals(apply(parallel, "C", "Am", "Cmaj7", "Dm7", "Bdim", "Csus4"), [
    "Cm",
    "A",
    "CmMaj7",
    "D7",
    undefined,
    undefined,
  ]);
});

Deno.test("relative moves a minor third, keeping the shared notes", () => {
  assertEquals(apply(relative, "C", "Cmaj7", "Am", "Am7", "Eb", "G7", "Bdim"), [
    "Am",
    "Am7",
    "C",
    "Cmaj7",
    "Cm",
    undefined,
    undefined,
  ]);
});

Deno.test("tritone substitution only applies to dominants", () => {
  assertEquals(apply(tritoneSub, "G7", "D9", "C", "Cmaj7"), [
    "D♭7",
    "A♭9",
    undefined,
    undefined,
  ]);
});

Deno.test("sevenths come from the key", () => {
  const seventh = (s: string, k = C) => chordName(toggleSeventh(parseChord(s, k)!, k)!);
  assertEquals(
    ["C", "Dm", "G", "Bdim", "F"].map(s => seventh(s)),
    ["Cmaj7", "Dm7", "G7", "Bm7♭5", "Fmaj7"],
  );
  assertEquals(seventh("E", key("A", "harmonicMinor")), "E7");
  assertEquals(seventh("G#dim", key("A", "harmonicMinor")), "G♯dim7");
  // outside the key: whichever seventh the key has
  assertEquals([seventh("Bb"), seventh("E"), seventh("Ab")], ["B♭maj7", "E7", "A♭maj7"]);
  assertEquals(
    ["Cmaj7", "G7", "Bdim7"].map(s => seventh(s)),
    ["C", "G", "Bdim"],
  );
});

Deno.test("suspending, and unsuspending back to the key's third", () => {
  const sus = (s: string, tone: 2 | 5) => chordName(suspend(parseChord(s, C)!, C, tone)!);
  assertEquals([sus("C", 5), sus("Am", 2), sus("G7", 5)], ["Csus4", "Asus2", "G7sus4"]);
  assertEquals([sus("Csus4", 5), sus("Dsus4", 5), sus("Csus2", 5)], ["C", "Dm", "Csus4"]);
});