import type { LameInternalFlags } from './LameInternalFlags';
import { BLKSIZE, BLKSIZE_s } from './constants';

export class FFT {
	private window: Float32Array = new Float32Array(BLKSIZE);

	private window_s: Float32Array = new Float32Array(BLKSIZE_s / 2);

	private readonly costab = [
		9.238795325112867e-1, 3.826834323650898e-1, 9.951847266721969e-1, 9.80171403295606e-2, 9.996988186962042e-1, 2.454122852291229e-2,
		9.999811752826011e-1, 6.135884649154475e-3,
	] as const;

	private fht(fz: Float32Array, fzPos: number, n: number) {
		let tri = 0;
		let k4: number;
		let fi: number;
		let gi: number;

		n <<= 1;

		const fn = fzPos + n;
		k4 = 4;
		do {
			let s1;
			let c1;
			let i;
			const kx = k4 >> 1;
			const k1 = k4;
			const k2 = k4 << 1;
			const k3 = k2 + k1;
			k4 = k2 << 1;
			fi = fzPos;
			gi = fi + kx;
			do {
				let f0;
				let f1;
				let f2;
				let f3;
				f1 = fz[fi + 0] - fz[fi + k1];
				f0 = fz[fi + 0] + fz[fi + k1];
				f3 = fz[fi + k2] - fz[fi + k3];
				f2 = fz[fi + k2] + fz[fi + k3];
				fz[fi + k2] = f0 - f2;
				fz[fi + 0] = f0 + f2;
				fz[fi + k3] = f1 - f3;
				fz[fi + k1] = f1 + f3;
				f1 = fz[gi + 0] - fz[gi + k1];
				f0 = fz[gi + 0] + fz[gi + k1];
				f3 = Math.SQRT2 * fz[gi + k3];
				f2 = Math.SQRT2 * fz[gi + k2];
				fz[gi + k2] = f0 - f2;
				fz[gi + 0] = f0 + f2;
				fz[gi + k3] = f1 - f3;
				fz[gi + k1] = f1 + f3;
				gi += k4;
				fi += k4;
			} while (fi < fn);
			c1 = this.costab[tri + 0];
			s1 = this.costab[tri + 1];
			for (i = 1; i < kx; i++) {
				let c2: number = 1 - 2 * s1 * s1;
				const s2 = 2 * s1 * c1;
				fi = fzPos + i;
				gi = fzPos + k1 - i;
				do {
					let a: number;
					let b: number;
					b = s2 * fz[fi + k1] - c2 * fz[gi + k1];
					a = c2 * fz[fi + k1] + s2 * fz[gi + k1];
					const f1 = fz[fi + 0] - a;
					const f0 = fz[fi + 0] + a;
					const g1 = fz[gi + 0] - b;
					const g0 = fz[gi + 0] + b;
					b = s2 * fz[fi + k3] - c2 * fz[gi + k3];
					a = c2 * fz[fi + k3] + s2 * fz[gi + k3];
					const f3 = fz[fi + k2] - a;
					const f2 = fz[fi + k2] + a;
					const g3 = fz[gi + k2] - b;
					const g2 = fz[gi + k2] + b;
					b = s1 * f2 - c1 * g3;
					a = c1 * f2 + s1 * g3;
					fz[fi + k2] = f0 - a;
					fz[fi + 0] = f0 + a;
					fz[gi + k3] = g1 - b;
					fz[gi + k1] = g1 + b;
					b = c1 * g2 - s1 * f3;
					a = s1 * g2 + c1 * f3;
					fz[gi + k2] = g0 - a;
					fz[gi + 0] = g0 + a;
					fz[fi + k3] = f1 - b;
					fz[fi + k1] = f1 + b;
					gi += k4;
					fi += k4;
				} while (fi < fn);
				c2 = c1;
				c1 = c2 * this.costab[tri + 0] - s1 * this.costab[tri + 1];
				s1 = c2 * this.costab[tri + 1] + s1 * this.costab[tri + 0];
			}
			tri += 2;
		} while (k4 < n);
	}

	private readonly rv_tbl = [
		0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0, 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8,
		0x68, 0xe8, 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8, 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4,
		0x34, 0xb4, 0x74, 0xf4, 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc, 0x02, 0x82,
		0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2, 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
		0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa, 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6,
		0x76, 0xf6, 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
	] as const;

	fft_short(_gfc: LameInternalFlags, x_real: Float32Array[], chn: number, buffer: Float32Array[], bufPos: number) {
		for (let b = 0; b < 3; b++) {
			let x = BLKSIZE_s / 2;
			const k = 0xffff & ((576 / 3) * (b + 1));
			let j = BLKSIZE_s / 8 - 1;
			do {
				let f0;
				let f1;
				let f2;
				let f3;
				let w;
				const i = this.rv_tbl[j << 2] & 0xff;

				f0 = this.window_s[i] * buffer[chn][bufPos + i + k];
				w = this.window_s[0x7f - i] * buffer[chn][bufPos + i + k + 0x80];
				f1 = f0 - w;
				f0 += w;
				f2 = this.window_s[i + 0x40] * buffer[chn][bufPos + i + k + 0x40];
				w = this.window_s[0x3f - i] * buffer[chn][bufPos + i + k + 0xc0];
				f3 = f2 - w;
				f2 += w;

				x -= 4;
				x_real[b][x + 0] = f0 + f2;
				x_real[b][x + 2] = f0 - f2;
				x_real[b][x + 1] = f1 + f3;
				x_real[b][x + 3] = f1 - f3;

				f0 = this.window_s[i + 0x01] * buffer[chn][bufPos + i + k + 0x01];
				w = this.window_s[0x7e - i] * buffer[chn][bufPos + i + k + 0x81];
				f1 = f0 - w;
				f0 += w;
				f2 = this.window_s[i + 0x41] * buffer[chn][bufPos + i + k + 0x41];
				w = this.window_s[0x3e - i] * buffer[chn][bufPos + i + k + 0xc1];
				f3 = f2 - w;
				f2 += w;

				x_real[b][x + BLKSIZE_s / 2 + 0] = f0 + f2;
				x_real[b][x + BLKSIZE_s / 2 + 2] = f0 - f2;
				x_real[b][x + BLKSIZE_s / 2 + 1] = f1 + f3;
				x_real[b][x + BLKSIZE_s / 2 + 3] = f1 - f3;
			} while (--j >= 0);

			this.fht(x_real[b], x, BLKSIZE_s / 2);
		}
	}

	fft_long(_gfc: LameInternalFlags, y: Float32Array, chn: number, buffer: Float32Array[], bufPos: number) {
		let jj = BLKSIZE / 8 - 1;
		let x = BLKSIZE / 2;

		do {
			let f0;
			let f1;
			let f2;
			let f3;
			let w;
			const i = this.rv_tbl[jj] & 0xff;
			f0 = this.window[i] * buffer[chn][bufPos + i];
			w = this.window[i + 0x200] * buffer[chn][bufPos + i + 0x200];
			f1 = f0 - w;
			f0 += w;
			f2 = this.window[i + 0x100] * buffer[chn][bufPos + i + 0x100];
			w = this.window[i + 0x300] * buffer[chn][bufPos + i + 0x300];
			f3 = f2 - w;
			f2 += w;

			x -= 4;
			y[x + 0] = f0 + f2;
			y[x + 2] = f0 - f2;
			y[x + 1] = f1 + f3;
			y[x + 3] = f1 - f3;

			f0 = this.window[i + 0x001] * buffer[chn][bufPos + i + 0x001];
			w = this.window[i + 0x201] * buffer[chn][bufPos + i + 0x201];
			f1 = f0 - w;
			f0 += w;
			f2 = this.window[i + 0x101] * buffer[chn][bufPos + i + 0x101];
			w = this.window[i + 0x301] * buffer[chn][bufPos + i + 0x301];
			f3 = f2 - w;
			f2 += w;

			y[x + BLKSIZE / 2 + 0] = f0 + f2;
			y[x + BLKSIZE / 2 + 2] = f0 - f2;
			y[x + BLKSIZE / 2 + 1] = f1 + f3;
			y[x + BLKSIZE / 2 + 3] = f1 - f3;
		} while (--jj >= 0);

		this.fht(y, x, BLKSIZE / 2);
	}

	init() {
		for (let i = 0; i < BLKSIZE; i++) {
			this.window[i] = 0.42 - 0.5 * Math.cos((2 * Math.PI * (i + 0.5)) / BLKSIZE) + 0.08 * Math.cos((4 * Math.PI * (i + 0.5)) / BLKSIZE);
		}

		for (let i = 0; i < BLKSIZE_s / 2; i++) {
			this.window_s[i] = 0.5 * (1.0 - Math.cos((2.0 * Math.PI * (i + 0.5)) / BLKSIZE_s));
		}
	}
}