nf.js

// https://unicode.org/reports/tr15/
// for reference implementation
// see: /derive/nf.js

import COMPRESSED from './include-nf.js';
import {read_compressed_payload, read_sorted, read_sorted_arrays, read_mapped} from './decoder.js';

// algorithmic hangul
// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf (page 144)
const S0 = 0xAC00;
const L0 = 0x1100;
const V0 = 0x1161;
const T0 = 0x11A7;
const L_COUNT = 19;
const V_COUNT = 21;
const T_COUNT = 28;
const N_COUNT = V_COUNT * T_COUNT;
const S_COUNT = L_COUNT * N_COUNT;
const S1 = S0 + S_COUNT;
const L1 = L0 + L_COUNT;
const V1 = V0 + V_COUNT;
const T1 = T0 + T_COUNT;

function unpack_cc(packed) {
	return (packed >> 24) & 0xFF;
}
function unpack_cp(packed) {
	return packed & 0xFFFFFF;
}

let SHIFTED_RANK, EXCLUSIONS, DECOMP, RECOMP;

function init() {
	//console.time('nf');
	let r = read_compressed_payload(COMPRESSED);
	SHIFTED_RANK = new Map(read_sorted_arrays(r).flatMap((v, i) => v.map(x => [x, (i+1) << 24]))); // pre-shifted
	EXCLUSIONS = new Set(read_sorted(r));
	DECOMP = new Map();
	RECOMP = new Map();
	for (let [cp, cps] of read_mapped(r)) {
		if (!EXCLUSIONS.has(cp) && cps.length == 2) {
			let [a, b] = cps;
			let bucket = RECOMP.get(a);
			if (!bucket) {
				bucket = new Map();
				RECOMP.set(a, bucket);
			}
			bucket.set(b, cp);
		}
		DECOMP.set(cp, cps.reverse()); // stored reversed
	}
	//console.timeEnd('nf');
	// 20230905: 11ms
}

function is_hangul(cp) {
	return cp >= S0 && cp < S1;
}

function compose_pair(a, b) {
	if (a >= L0 && a < L1 && b >= V0 && b < V1) {
		return S0 + (a - L0) * N_COUNT + (b - V0) * T_COUNT;
	} else if (is_hangul(a) && b > T0 && b < T1 && (a - S0) % T_COUNT == 0) {
		return a + (b - T0);
	} else {
		let recomp = RECOMP.get(a);
		if (recomp) {
			recomp = recomp.get(b);
			if (recomp) {
				return recomp;
			}
		}
		return -1;
	}
}

function decomposed(cps) {
	if (!SHIFTED_RANK) init();
	let ret = [];
	let buf = [];
	let check_order = false;
	function add(cp) {
		let cc = SHIFTED_RANK.get(cp);
		if (cc) {
			check_order = true;
			cp |= cc;
		}
		ret.push(cp);
	}
	for (let cp of cps) {
		while (true) {
			if (cp < 0x80) {
				ret.push(cp);
			} else if (is_hangul(cp)) {
				let s_index = cp - S0;
				let l_index = s_index / N_COUNT | 0;
				let v_index = (s_index % N_COUNT) / T_COUNT | 0;
				let t_index = s_index % T_COUNT;
				add(L0 + l_index);
				add(V0 + v_index);
				if (t_index > 0) add(T0 + t_index);
			} else {
				let mapped = DECOMP.get(cp);
				if (mapped) {
					buf.push(...mapped);
				} else {
					add(cp);
				}
			}
			if (!buf.length) break;
			cp = buf.pop();
		}
	}
	if (check_order && ret.length > 1) {
		let prev_cc = unpack_cc(ret[0]);
		for (let i = 1; i < ret.length; i++) {
			let cc = unpack_cc(ret[i]);
			if (cc == 0 || prev_cc <= cc) {
				prev_cc = cc;
				continue;
			}
			let j = i-1;
			while (true) {
				let tmp = ret[j+1];
				ret[j+1] = ret[j];
				ret[j] = tmp;
				if (!j) break;
				prev_cc = unpack_cc(ret[--j]);
				if (prev_cc <= cc) break;
			}
			prev_cc = unpack_cc(ret[i]);
		}
	}
	return ret;
}

function composed_from_decomposed(v) {
	let ret = [];
	let stack = [];
	let prev_cp = -1;
	let prev_cc = 0;
	for (let packed of v) {
		let cc = unpack_cc(packed);
		let cp = unpack_cp(packed);
		if (prev_cp == -1) {
			if (cc == 0) {
				prev_cp = cp;
			} else {
				ret.push(cp);
			}
		} else if (prev_cc > 0 && prev_cc >= cc) {
			if (cc == 0) {
				ret.push(prev_cp, ...stack);
				stack.length = 0;
				prev_cp = cp;
			} else {
				stack.push(cp);
			}
			prev_cc = cc;
		} else {
			let composed = compose_pair(prev_cp, cp);
			if (composed >= 0) {
				prev_cp = composed;
			} else if (prev_cc == 0 && cc == 0) {
				ret.push(prev_cp);
				prev_cp = cp;
			} else {
				stack.push(cp);
				prev_cc = cc;
			}
		}
	}
	if (prev_cp >= 0) {
		ret.push(prev_cp, ...stack);	
	}
	return ret;
}

// note: cps can be iterable
export function nfd(cps) {
	return decomposed(cps).map(unpack_cp);
}
export function nfc(cps) {
	return composed_from_decomposed(decomposed(cps));
}