/* 
 * Optimal text segmentation for QR Codes
 * 
 * Copyright (c) 2022 Project Nayuki
 * All rights reserved. Contact Nayuki for licensing.
 * https://www.nayuki.io/page/optimal-text-segmentation-for-qr-codes
 */


namespace app {
	
	/*---- Preamble definitions ----*/
	
	type int = number;
	type Mode = "BYTE" | "NUMERIC" | "ALPHANUMERIC" | "KANJI";
	
	
	function getElem(id: string): HTMLElement {
		const result: HTMLElement|null = document.getElementById(id);
		if (result instanceof HTMLElement)
			return result;
		throw new Error("Assertion error");
	}
	
	
	function getInput(id: string): HTMLInputElement {
		const result: HTMLElement = getElem(id);
		if (result instanceof HTMLInputElement)
			return result;
		throw new Error("Assertion error");
	}
	
	
	const userTextInputElem = getElem("user-text-input") as HTMLTextAreaElement;
	const demoTextElem = getElem("demo-text") as HTMLSelectElement;
	
	
	
	/*---- Entry points from HTML page ----*/
	
	export function demoChanged(): void {
		userTextInputElem.value = demoTextElem.value;
		textChanged();
	}
	
	
	export function textChanged(): void {
		const textStr: string = userTextInputElem.value;
		if (textStr != demoTextElem.value)
			demoTextElem.selectedIndex = 0;  // Indicates custom input
		const minVersion: int = parseInt(getInput("minimum-version").value, 10);
		let errCorrLvl: int;
		if      (getInput("errcorlvl-low"     ).checked)  errCorrLvl = 0;
		else if (getInput("errcorlvl-medium"  ).checked)  errCorrLvl = 1;
		else if (getInput("errcorlvl-quartile").checked)  errCorrLvl = 2;
		else if (getInput("errcorlvl-high"    ).checked)  errCorrLvl = 3;
		else  throw new Error("Assertion error");
		
		// Handle code points
		const codePoints: Array<CodePoint> = CodePoint.toArray(textStr);
		setText("num-code-points", codePoints.length);
		
		// Process the byte-only segmentation algorithm
		const byteOnlyInfo = makeSingleByteSegment(codePoints, errCorrLvl, minVersion, 40);
		if (byteOnlyInfo === null) {
			setText("qr-code-version-byte-only", "Too long");
			setText("num-segments-byte-only", "N/A");
			setText("total-segment-bits-byte-only", "N/A");
		} else {
			const [version, segs] = byteOnlyInfo;
			setText("qr-code-version-byte-only", version);
			setText("num-segments-byte-only", segs.length);
			setText("total-segment-bits-byte-only", getTotalBits(segs, version));
		}
		
		// Clear container elements
		const textOut = getElem("text-split");
		const tableOut = document.querySelector("#segment-details tbody") as HTMLElement;
		while (textOut.firstChild !== null)
			textOut.removeChild(textOut.firstChild);
		while (tableOut.firstChild !== null)
			tableOut.removeChild(tableOut.firstChild);
		
		// Process the optimal segmentation algorithm
		const optimalInfo = makeSegmentsOptimally(codePoints, errCorrLvl, minVersion, 40);
		if (optimalInfo === null) {
			setText("qr-code-version-optimal", "Too long");
			setText("num-segments-optimal", "N/A");
			setText("total-segment-bits-optimal", "N/A");
		} else {
			const [version, segs] = optimalInfo;
			setText("qr-code-version-optimal", version);
			setText("num-segments-optimal", segs.length);
			setText("total-segment-bits-optimal", getTotalBits(segs, version));
			
			segs.forEach((seg: Segment, i: int) => {
				let span = textOut.appendChild(document.createElement("span"));
				span.textContent = seg.text;
				span.classList.add(seg.mode.toLowerCase());
				span.title = "Segment index: " + i;
				
				let tr = tableOut.appendChild(document.createElement("tr"));
				tr.classList.add(seg.mode.toLowerCase());
				const cells: Array<string|int> = [
					i,
					seg.mode.charAt(0) + seg.mode.substring(1).toLowerCase(),
					getTotalBits([seg], version) - seg.numDataBits,
					seg.numDataBits,
					getTotalBits([seg], version),
					seg.numChars,
					seg.text,
				];
				for (const s of cells) {
					const td = tr.appendChild(document.createElement("td"));
					td.textContent = s.toString();
				}
			});
		}
		
		// Process the comparison between segmentation algorithms
		if (byteOnlyInfo === null || optimalInfo === null) {
			const INFINITY = "\u221E";
			setText("qr-code-version-savings", INFINITY);
			setText("total-segment-bits-savings", INFINITY);
		} else {
			setText("qr-code-version-savings", byteOnlyInfo[0] - optimalInfo[0]);
			const byteOnlyBits = getTotalBits(byteOnlyInfo[1], byteOnlyInfo[0]);
			const optimalBits  = getTotalBits(optimalInfo [1], optimalInfo [0]);
			setText("total-segment-bits-savings", `${byteOnlyBits - optimalBits} (${(optimalBits / byteOnlyBits).toFixed(2)}\u00D7)`);
		}
	}
	
	
	export function revealElement(link: HTMLElement, targetId: string): boolean {
		let linkParent = link.parentNode as HTMLElement;
		while (link.firstChild !== null)
			linkParent.append(link.firstChild);
		link.remove();
		
		let target = getElem(targetId);
		target.style.removeProperty("display");
		const newHeight: number = target.clientHeight;
		target.style.height = "0px";
		target.style.overflow = "hidden";
		target.style.transition = "height 0.5s ease-in-out";
		target.addEventListener("transitionend", ev => {
			if (ev.propertyName == "height") {
				target.style.removeProperty("height");
				target.style.removeProperty("overflow");
				target.style.removeProperty("transition");
			}
		});
		target.clientHeight;  // Read property to force reflow in Firefox
		target.style.height = newHeight + "px";
		return false;
	}
	
	
	
	/*---- High-level computation functions ----*/
	
	function makeSingleByteSegment(text: Readonly<Array<CodePoint>>, ecl: int,
			minVersion: int, maxVersion: int):
			[int,Array<Segment>]|null {
		
		if (!(0 <= ecl && ecl <= 3))
			throw new RangeError("Invalid error correction level");
		if (!(1 <= minVersion && minVersion <= maxVersion && maxVersion <= 40))
			throw new RangeError("Invalid version range");
		
		// Iterate through version numbers, and make tentative segments
		const segs: Array<Segment> = [new Segment(text, "BYTE")];
		for (let version = minVersion; version <= maxVersion; version++) {
			// Check if the segments fit
			const dataCapacityBits: int = NUM_DATA_CODEWORDS[version][ecl] * 8;
			const dataUsedBits: number = getTotalBits(segs, version);
			if (dataUsedBits <= dataCapacityBits)
				return [version, segs];
		}
		// The data is too long to fit in any QR Code symbol at any version in
		// the range [minVersion, maxVersion] with ecl level error correction
		return null;
	}
	
	
	// Returns a new array of zero or more segments to represent the given Unicode text string.
	// The resulting array optimally minimizes the total encoded bit length, subjected to the
	// constraints in the given {error correction level, minimum version number, maximum version number}.
	// This function can utilize all four text encoding modes: numeric, alphanumeric, byte (UTF-8), and kanji.
	function makeSegmentsOptimally(text: Readonly<Array<CodePoint>>, ecl: int,
			minVersion: int, maxVersion: int):
			[int,Array<Segment>]|null {
		
		if (!(0 <= ecl && ecl <= 3))
			throw new RangeError("Invalid error correction level");
		if (!(1 <= minVersion && minVersion <= maxVersion && maxVersion <= 40))
			throw new RangeError("Invalid version range");
		
		// Iterate through version numbers, and make tentative segments
		let segs: Array<Segment> = [];  // Dummy initial value
		for (let version = minVersion; version <= maxVersion; version++) {
			if (version == minVersion || version == 10 || version == 27)
				segs = makeSegmentsOptimallyForVersion(text, version);
			
			// Check if the segments fit
			const dataCapacityBits: int = NUM_DATA_CODEWORDS[version][ecl] * 8;
			const dataUsedBits: number = getTotalBits(segs, version);
			if (dataUsedBits <= dataCapacityBits)
				return [version, segs];
		}
		// The data is too long to fit in any QR Code symbol at any version in
		// the range [minVersion, maxVersion] with ecl level error correction
		return null;
	}
	
	
	// Returns a new array of segments that is optimal for the given text at the given version number.
	function makeSegmentsOptimallyForVersion(text: Readonly<Array<CodePoint>>, version: int): Array<Segment> {
		if (text.length == 0)
			return [];
		const charModes = computeCharacterModes(text, version);
		return splitIntoSegments(text, charModes);
	}
	
	
	// Returns a new array representing the optimal mode per code point based on the given text and version.
	function computeCharacterModes(text: Readonly<Array<CodePoint>>, version: int): Array<Mode> {
		if (text.length == 0)
			throw new RangeError("Empty string");
		const modeTypes: Array<Mode> = ["BYTE", "ALPHANUMERIC", "NUMERIC", "KANJI"];
		
		// Segment header sizes, measured in 1/6 bits
		const headCosts: Array<int> = modeTypes.map(mode =>
			(4 + getNumCharCountBits(mode, version)) * 6);
		
		// charModes[i][j] represents the mode to encode the code point at
		// index i such that the final segment ends in modeTypes[j] and the
		// total number of bits is minimized over all possible choices
		let charModes: Array<Array<Mode>> = [];
		
		// At the beginning of each iteration of the loop below,
		// prevCosts[j] is the exact minimum number of 1/6 bits needed to
		// encode the entire string prefix of length i, and end in modeTypes[j]
		let prevCosts: Array<int> = headCosts.slice();
		
		// Calculate costs using dynamic programming
		for (const c of text) {
			let cModes: Array<Mode|null> = modeTypes.map(_ => null);
			
			let curCosts: Array<int> = modeTypes.map(_ => Infinity);
			{  // Always extend a byte mode segment
				curCosts[0] = prevCosts[0] + c.utf8.length * 8 * 6;
				cModes[0] = modeTypes[0];
			}
			// Extend a segment if possible
			if (isAlphanumeric(c.utf32)) {
				curCosts[1] = prevCosts[1] + 33;  // 5.5 bits per alphanumeric char
				cModes[1] = modeTypes[1];
			}
			if (isNumeric(c.utf32)) {
				curCosts[2] = prevCosts[2] + 20;  // 3.33 bits per digit
				cModes[2] = modeTypes[2];
			}
			if (isKanji(c.utf32)) {
				curCosts[3] = prevCosts[3] + 78;  // 13 bits per Shift JIS char
				cModes[3] = modeTypes[3];
			}
			
			// Start new segment at the end to switch modes
			modeTypes.forEach((_, j) => {  // To mode
				modeTypes.forEach((fromMode, k) => {  // From mode
					const newCost = Math.ceil(curCosts[k] / 6) * 6 + headCosts[j];
					if (cModes[k] !== null && newCost < curCosts[j]) {
						curCosts[j] = newCost;
						cModes[j] = fromMode;
					}
				});
			});
			
			charModes.push(cModes as Array<Mode>);
			prevCosts = curCosts;
		}
		
		// Find optimal ending mode
		let curModeIndex: int = 0;
		modeTypes.forEach((mode, i) => {
			if (prevCosts[i] < prevCosts[curModeIndex])
				curModeIndex = i;
		});
		
		// Get optimal mode for each code point by tracing backwards
		let result: Array<Mode> = [];
		for (let i = text.length - 1; i >= 0; i--) {
			const curMode = charModes[i][curModeIndex];
			curModeIndex = modeTypes.indexOf(curMode);
			result.push(curMode);
		}
		result.reverse();
		return result;
	}
	
	
	// Returns a new array of segments based on the given text and modes, such that
	// consecutive code points in the same mode are put into the same segment.
	function splitIntoSegments(text: Readonly<Array<CodePoint>>, charModes: Readonly<Array<Mode>>): Array<Segment> {
		if (text.length == 0)
			throw new RangeError("Empty string");
		if (text.length != charModes.length)
			throw new RangeError("Mismatched lengths");
		let result: Array<Segment> = [];
		
		// Accumulate run of modes
		let curMode: Mode = charModes[0];
		let start: int = 0;
		for (let i = 1; ; i++) {
			if (i < text.length && charModes[i] == curMode)
				continue;
			result.push(new Segment(text.slice(start, i), curMode));
			if (i >= text.length)
				return result;
			curMode = charModes[i];
			start = i;
		}
	}
	
	
	class Segment {
		public readonly numChars: int;
		public readonly text: string;
		public readonly numDataBits: int;
		
		public constructor(
				text: Readonly<Array<CodePoint>>,
				public readonly mode: Mode) {
			
			this.text = text.map(c => c.utf16).join("");
			if (mode == "BYTE") {
				this.numChars = 0;
				for (const c of text)
					this.numChars += c.utf8.length;
				this.numDataBits = this.numChars * 8;
			} else {
				this.numChars = text.length;
				switch (mode) {
					case "NUMERIC":
						this.numDataBits = Math.ceil(this.numChars * 10 / 3);
						break;
					case "ALPHANUMERIC":
						this.numDataBits = Math.ceil(this.numChars * 11 / 2);
						break;
					case "KANJI":
						this.numDataBits = this.numChars * 13;
						break;
					default:
						throw new RangeError("Invalid mode");
				}
			}
		}
	}
	
	
	// Calculates and returns the number of bits needed to encode the given segments at the given
	// version. The result is infinity if a segment has too many characters to fit its length field.
	function getTotalBits(segs: Readonly<Array<Segment>>, version: int): number {
		let result: int = 0;
		for (const seg of segs) {
			const ccbits: int = getNumCharCountBits(seg.mode, version);
			if (seg.numChars >= (1 << ccbits))
				return Infinity;  // The segment's length doesn't fit the field's bit width
			result += 4 + ccbits + seg.numDataBits;
		}
		return result;
	}
	
	
	
	/*---- Low-level computation functions ----*/
	
	// Returns the bit width of the character count field for a segment
	// in the given mode in a QR Code at the given version number.
	function getNumCharCountBits(mode: Mode, version: int): int {
		if (version < 1 || version > 40)
			throw new RangeError("Invalid version");
		return {
			NUMERIC     : [10, 12, 14],
			ALPHANUMERIC: [ 9, 11, 13],
			BYTE        : [ 8, 16, 16],
			KANJI       : [ 8, 10, 12],
		}[mode][Math.floor((version + 7) / 17)];
	}
	
	
	// NUM_DATA_CODEWORDS[v][e] is the number of 8-bit data codewords (excluding error correction codewords)
	// in a QR Code symbol at version v (from 1 to 40 inclusive) and error correction e (0=L, 1=M, 2=Q, 3=H).
	const NUM_DATA_CODEWORDS: Array<[int,int,int,int]> = [
		//  L,    M,    Q,    H    // Error correction level
		[  -1,   -1,   -1,   -1],  // Padding for index 0
		[  19,   16,   13,    9],  // Version 01
		[  34,   28,   22,   16],  // Version 02
		[  55,   44,   34,   26],  // Version 03
		[  80,   64,   48,   36],  // Version 04
		[ 108,   86,   62,   46],  // Version 05
		[ 136,  108,   76,   60],  // Version 06
		[ 156,  124,   88,   66],  // Version 07
		[ 194,  154,  110,   86],  // Version 08
		[ 232,  182,  132,  100],  // Version 09
		[ 274,  216,  154,  122],  // Version 10
		[ 324,  254,  180,  140],  // Version 11
		[ 370,  290,  206,  158],  // Version 12
		[ 428,  334,  244,  180],  // Version 13
		[ 461,  365,  261,  197],  // Version 14
		[ 523,  415,  295,  223],  // Version 15
		[ 589,  453,  325,  253],  // Version 16
		[ 647,  507,  367,  283],  // Version 17
		[ 721,  563,  397,  313],  // Version 18
		[ 795,  627,  445,  341],  // Version 19
		[ 861,  669,  485,  385],  // Version 20
		[ 932,  714,  512,  406],  // Version 21
		[1006,  782,  568,  442],  // Version 22
		[1094,  860,  614,  464],  // Version 23
		[1174,  914,  664,  514],  // Version 24
		[1276, 1000,  718,  538],  // Version 25
		[1370, 1062,  754,  596],  // Version 26
		[1468, 1128,  808,  628],  // Version 27
		[1531, 1193,  871,  661],  // Version 28
		[1631, 1267,  911,  701],  // Version 29
		[1735, 1373,  985,  745],  // Version 30
		[1843, 1455, 1033,  793],  // Version 31
		[1955, 1541, 1115,  845],  // Version 32
		[2071, 1631, 1171,  901],  // Version 33
		[2191, 1725, 1231,  961],  // Version 34
		[2306, 1812, 1286,  986],  // Version 35
		[2434, 1914, 1354, 1054],  // Version 36
		[2566, 1992, 1426, 1096],  // Version 37
		[2702, 2102, 1502, 1142],  // Version 38
		[2812, 2216, 1582, 1222],  // Version 39
		[2956, 2334, 1666, 1276],  // Version 40
	];
	
	
	// Tests whether the given code point can be encoded in numeric mode.
	function isNumeric(cp: int): boolean {
		return cp < 128 && "0123456789".includes(String.fromCodePoint(cp));
	}
	
	
	// Tests whether the given code point can be encoded in alphanumeric mode.
	function isAlphanumeric(cp: int): boolean {
		return cp < 128 && "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:".includes(String.fromCodePoint(cp));
	}
	
	
	// Tests whether the given code point can be encoded in kanji mode.
	function isKanji(cp: int): boolean {
		return cp < 0x10000 && ((parseInt(KANJI_BIT_SET.charAt(cp >>> 2), 16) >>> (cp & 3)) & 1) != 0;
	}
	
	
	const KANJI_BIT_SET: string =
		"0000000000000000000000010000000000000000C811350000000800000008000000000000000000000000000000000000000000000000000000000000000000" +
		"0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000EFFFBF30EFFFBF30000000000000" +
		"2000FFFFFFFFFFFFFFFF200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
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		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"000016333600D080000000000000000000000000000000000000000000000000800000000080000000000000000000000000F000000000000000410000000000" +
		"D890404618F10302000040003CC00000CC0000000200000000000000000000000000400000000000000000000000000000000000000000000000000000000000" +
		"0000000000000000000000000000000000000000000000000000000000000000F0099993939999994080000000000000000000003000C0030C8C000000080000" +
		"060000000000000050000000004A0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
		"FEFFF30100000000EFFFFFFFFFFFFFFFFFFFF087EFFFFFFFFFFFFFFFFFFFF7870000000000000000000000000000000000000000000000000000000000000000" +
		"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
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		"06AA6568A7F304208838164102014712120220700003CB04426A26448A0602A071204758204048C9BFB7514142F72E11566BFE2057F1FF0207A304833C623676" +
		"9DD429020B649CF089CB05848368F30A8832618890E32325AA224A3EDD00C27C661A1E62B048A0F8BE72E955142CBB984100045816369480C0F70DA8E3FFFC50" +
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		"040A8C010413054440040010082804508010C24403A650A16A024150FC0965461200001381C90FBC021A2E36C4015B10C83538A92B8B1823A78948A07E3320C0" +
		"CC4D81091A1A0709E1A8400E4D3C1540A9342C1244840135292004631420DB3F90BA0F8E0CD72D5A242CB42DF34AFA0D0AA11A4374288D30254CB156492DA38C" +
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		"42C1C9ACE0E40672099000386400401811061801D0458090E000A0CC005000C00340440AB8004876882591A8E56881B895E2061401C8EBC91686C19800898000" +
		"0018A9808100091470041A4E5050D046E013D4E06084A0FF23618AA2E258B000008148AC02E0C6962300006185650930021582A1000842111E81623425D5AAE0" +
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		"20A822DE0C015004000120108088101300644020000F80700098002A000020220020016124000401002506204F250002015803280011202480345B081E0702A9" +
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	/*---- Helper class ----*/
	
	class CodePoint {
		
		public static toArray(s: string): Array<CodePoint> {
			let result: Array<CodePoint> = [];
			for (const ch of s) {
				const cc = ch.codePointAt(0) as int;
				if (0xD800 <= cc && cc < 0xE000)
					throw new RangeError("Invalid UTF-16 string");
				result.push(new CodePoint(cc));
			}
			return result;
		}
		
		
		public readonly utf8: Array<int>;
		public readonly utf16: string;
		
		private constructor(
				public readonly utf32: int) {
			
			this.utf16 = String.fromCodePoint(utf32);
			
			if (utf32 < 0)
				throw new RangeError("Invalid code point");
			else if (utf32 < 0x80)
				this.utf8 = [utf32];
			else {
				let n: int;
				if      (utf32 <    0x800)  n = 2;
				else if (utf32 <  0x10000)  n = 3;
				else if (utf32 < 0x110000)  n = 4;
				else  throw new RangeError("Invalid code point");
				this.utf8 = [];
				for (let i = 0; i < n; i++, utf32 >>>= 6)
					this.utf8.push(0x80 | (utf32 & 0x3F));
				this.utf8.reverse();
				this.utf8[0] |= (0xF00 >>> n) & 0xFF;
			}
		}
		
	}
	
	
	
	/*---- Miscellaneous ----*/
	
	function setText(id: string, text: string|int): void {
		getElem(id).textContent = text.toString();
	}
	
	
	// Initialization
	if (demoTextElem.value != "")
		demoChanged();
	else
		textChanged();
}