// Grapheme segmenter (shared instance)
const segmenter = new Intl.Segmenter(undefined, { granularity: "grapheme" });

/**
 * Get the shared grapheme segmenter instance.
 */
export function getSegmenter(): Intl.Segmenter {
	return segmenter;
}


// Cache for non-ASCII strings
const WIDTH_CACHE_SIZE = 512;
const widthCache = new Map<string, number>();


/**
 * Calculate the visible width of a string in terminal columns.
 */
export function visibleWidth(str: string): number {
	if (str.length === 0) {
		return 0;
	}

	// Fast path: pure ASCII printable
	let isPureAscii = true;
	for (let i = 0; i < str.length; i++) {
		const code = str.charCodeAt(i);
		if (code < 0x20 || code > 0x7e) {
			isPureAscii = false;
			break;
		}
	}
	if (isPureAscii) {
		return str.length;
	}

	// Check cache
	const cached = widthCache.get(str);
	if (cached !== undefined) {
		return cached;
	}

	// Normalize: tabs to 3 spaces, strip ANSI escape codes
	let clean = str;
	if (str.includes("\t")) {
		clean = clean.replace(/\t/g, "   ");
	}
	if (clean.includes("\x1b")) {
		// Strip SGR codes (\x1b[...m) and cursor codes (\x1b[...G/K/H/J)
		clean = clean.replace(/\x1b\[[0-9;]*[mGKHJ]/g, "");
		// Strip OSC 8 hyperlinks: \x1b]8;;URL\x07 and \x1b]8;;\x07
		clean = clean.replace(/\x1b\]8;;[^\x07]*\x07/g, "");
	}


	const width = Bun.stringWidth(clean);

	// Cache result
	if (widthCache.size >= WIDTH_CACHE_SIZE) {
		const firstKey = widthCache.keys().next().value;
		if (firstKey !== undefined) {
			widthCache.delete(firstKey);
		}
	}
	widthCache.set(str, width);

	return width;
}

/**
 * Extract ANSI escape sequences from a string at the given position.
 */
export function extractAnsiCode(str: string, pos: number): { code: string; length: number } | null {
	if (pos >= str.length || str[pos] !== "\x1b") return null;

	const next = str[pos + 1];

	// CSI sequence: ESC [ ... m/G/K/H/J
	if (next === "[") {
		let j = pos + 2;
		while (j < str.length && !/[mGKHJ]/.test(str[j]!)) j++;
		if (j < str.length) return { code: str.substring(pos, j + 1), length: j + 1 - pos };
		return null;
	}

	// OSC sequence: ESC ] ... BEL or ESC ] ... ST (ESC \)
	// Used for hyperlinks (OSC 8), window titles, etc.
	if (next === "]") {
		let j = pos + 2;
		while (j < str.length) {
			if (str[j] === "\x07") return { code: str.substring(pos, j + 1), length: j + 1 - pos };
			if (str[j] === "\x1b" && str[j + 1] === "\\") {
				return { code: str.substring(pos, j + 2), length: j + 2 - pos };
			}
			j++;
		}
		return null;
	}

	return null;
}

/**
 * Track active ANSI SGR codes to preserve styling across line breaks.
 */
class AnsiCodeTracker {
	// Track individual attributes separately so we can reset them specifically
	private bold = false;
	private dim = false;
	private italic = false;
	private underline = false;
	private blink = false;
	private inverse = false;
	private hidden = false;
	private strikethrough = false;
	private fgColor: string | null = null; // Stores the full code like "31" or "38;5;240"
	private bgColor: string | null = null; // Stores the full code like "41" or "48;5;240"

	process(ansiCode: string): void {
		if (!ansiCode.endsWith("m")) {
			return;
		}

		// Extract the parameters between \x1b[ and m
		const match = ansiCode.match(/\x1b\[([\d;]*)m/);
		if (!match) return;

		const params = match[1];
		if (params === "" || params === "0") {
			// Full reset
			this.reset();
			return;
		}

		// Parse parameters (can be semicolon-separated)
		const parts = params.split(";");
		let i = 0;
		while (i < parts.length) {
			const code = Number.parseInt(parts[i], 10);

			// Handle 256-color and RGB codes which consume multiple parameters
			if (code === 38 || code === 48) {
				// 38;5;N (256 color fg) or 38;2;R;G;B (RGB fg)
				// 48;5;N (256 color bg) or 48;2;R;G;B (RGB bg)
				if (parts[i + 1] === "5" && parts[i + 2] !== undefined) {
					// 256 color: 38;5;N or 48;5;N
					const colorCode = `${parts[i]};${parts[i + 1]};${parts[i + 2]}`;
					if (code === 38) {
						this.fgColor = colorCode;
					} else {
						this.bgColor = colorCode;
					}
					i += 3;
					continue;
				} else if (parts[i + 1] === "2" && parts[i + 4] !== undefined) {
					// RGB color: 38;2;R;G;B or 48;2;R;G;B
					const colorCode = `${parts[i]};${parts[i + 1]};${parts[i + 2]};${parts[i + 3]};${parts[i + 4]}`;
					if (code === 38) {
						this.fgColor = colorCode;
					} else {
						this.bgColor = colorCode;
					}
					i += 5;
					continue;
				}
			}

			// Standard SGR codes
			switch (code) {
				case 0:
					this.reset();
					break;
				case 1:
					this.bold = true;
					break;
				case 2:
					this.dim = true;
					break;
				case 3:
					this.italic = true;
					break;
				case 4:
					this.underline = true;
					break;
				case 5:
					this.blink = true;
					break;
				case 7:
					this.inverse = true;
					break;
				case 8:
					this.hidden = true;
					break;
				case 9:
					this.strikethrough = true;
					break;
				case 21:
					this.bold = false;
					break; // Some terminals
				case 22:
					this.bold = false;
					this.dim = false;
					break;
				case 23:
					this.italic = false;
					break;
				case 24:
					this.underline = false;
					break;
				case 25:
					this.blink = false;
					break;
				case 27:
					this.inverse = false;
					break;
				case 28:
					this.hidden = false;
					break;
				case 29:
					this.strikethrough = false;
					break;
				case 39:
					this.fgColor = null;
					break; // Default fg
				case 49:
					this.bgColor = null;
					break; // Default bg
				default:
					// Standard foreground colors 30-37, 90-97
					if ((code >= 30 && code <= 37) || (code >= 90 && code <= 97)) {
						this.fgColor = String(code);
					}
					// Standard background colors 40-47, 100-107
					else if ((code >= 40 && code <= 47) || (code >= 100 && code <= 107)) {
						this.bgColor = String(code);
					}
					break;
			}
			i++;
		}
	}

	private reset(): void {
		this.bold = false;
		this.dim = false;
		this.italic = false;
		this.underline = false;
		this.blink = false;
		this.inverse = false;
		this.hidden = false;
		this.strikethrough = false;
		this.fgColor = null;
		this.bgColor = null;
	}

	/** Clear all state for reuse. */
	clear(): void {
		this.reset();
	}

	getActiveCodes(): string {
		const codes: string[] = [];
		if (this.bold) codes.push("1");
		if (this.dim) codes.push("2");
		if (this.italic) codes.push("3");
		if (this.underline) codes.push("4");
		if (this.blink) codes.push("5");
		if (this.inverse) codes.push("7");
		if (this.hidden) codes.push("8");
		if (this.strikethrough) codes.push("9");
		if (this.fgColor) codes.push(this.fgColor);
		if (this.bgColor) codes.push(this.bgColor);

		if (codes.length === 0) return "";
		return `\x1b[${codes.join(";")}m`;
	}

	hasActiveCodes(): boolean {
		return (
			this.bold ||
			this.dim ||
			this.italic ||
			this.underline ||
			this.blink ||
			this.inverse ||
			this.hidden ||
			this.strikethrough ||
			this.fgColor !== null ||
			this.bgColor !== null
		);
	}

	/**
	 * Get reset codes for attributes that need to be turned off at line end,
	 * specifically underline which bleeds into padding.
	 * Returns empty string if no problematic attributes are active.
	 */
	getLineEndReset(): string {
		// Only underline causes visual bleeding into padding
		// Other attributes like colors don't visually bleed to padding
		if (this.underline) {
			return "\x1b[24m"; // Underline off only
		}
		return "";
	}
}



/**
 * Wrap text with ANSI codes preserved.
 *
 * ONLY does word wrapping - NO padding, NO background colors.
 * Returns lines where each line is <= width visible chars.
 * Active ANSI codes are preserved across line breaks.
 *
 * @param text - Text to wrap (may contain ANSI codes and newlines)
 * @param width - Maximum visible width per line
 * @returns Array of wrapped lines (NOT padded to width)
 */
export function wrapTextWithAnsi(text: string, width: number): string[] {
	if (!text) {
		return [""];
	}

	return Bun.wrapAnsi(text, width, { wordWrap: true, hard: true, trim: false }).split("\n");
}

const PUNCTUATION_REGEX = /[(){}[\]<>.,;:'"!?+\-=*/\\|&%^$#@~`]/;

/**
 * Check if a character is whitespace.
 */
export function isWhitespaceChar(char: string): boolean {
	return /\s/.test(char);
}

/**
 * Check if a character is punctuation.
 */
export function isPunctuationChar(char: string): boolean {
	return PUNCTUATION_REGEX.test(char);
}

/**
 * Apply background color to a line, padding to full width.
 *
 * @param line - Line of text (may contain ANSI codes)
 * @param width - Total width to pad to
 * @param bgFn - Background color function
 * @returns Line with background applied and padded to width
 */
export function applyBackgroundToLine(line: string, width: number, bgFn: (text: string) => string): string {
	// Calculate padding needed
	const visibleLen = visibleWidth(line);
	const paddingNeeded = Math.max(0, width - visibleLen);
	const padding = " ".repeat(paddingNeeded);

	// Apply background to content + padding
	const withPadding = line + padding;
	return bgFn(withPadding);
}

/**
 * Truncate text to fit within a maximum visible width, adding ellipsis if needed.
 * Optionally pad with spaces to reach exactly maxWidth.
 * Properly handles ANSI escape codes (they don't count toward width).
 *
 * @param text - Text to truncate (may contain ANSI codes)
 * @param maxWidth - Maximum visible width
 * @param ellipsis - Ellipsis string to append when truncating (default: "…")
 * @param pad - If true, pad result with spaces to exactly maxWidth (default: false)
 * @returns Truncated text, optionally padded to exactly maxWidth
 */
export function truncateToWidth(text: string, maxWidth: number, ellipsis: string = "…", pad: boolean = false): string {
	const textVisibleWidth = visibleWidth(text);

	if (textVisibleWidth <= maxWidth) {
		return pad ? text + " ".repeat(maxWidth - textVisibleWidth) : text;
	}

	const ellipsisWidth = visibleWidth(ellipsis);
	const targetWidth = maxWidth - ellipsisWidth;

	if (targetWidth <= 0) {
		return ellipsis.substring(0, maxWidth);
	}

	// Separate ANSI codes from visible content using grapheme segmentation
	let i = 0;
	const segments: Array<{ type: "ansi" | "grapheme"; value: string }> = [];

	while (i < text.length) {
		const ansiResult = extractAnsiCode(text, i);
		if (ansiResult) {
			segments.push({ type: "ansi", value: ansiResult.code });
			i += ansiResult.length;
		} else {
			// Find the next ANSI code or end of string
			let end = i;
			while (end < text.length) {
				const nextAnsi = extractAnsiCode(text, end);
				if (nextAnsi) break;
				end++;
			}
			// Segment this non-ANSI portion into graphemes
			const textPortion = text.slice(i, end);
			for (const seg of segmenter.segment(textPortion)) {
				segments.push({ type: "grapheme", value: seg.segment });
			}
			i = end;
		}
	}

	// Build truncated string from segments
	let result = "";
	let currentWidth = 0;

	for (const seg of segments) {
		if (seg.type === "ansi") {
			result += seg.value;
			continue;
		}

		const grapheme = seg.value;
		// Skip empty graphemes to avoid issues with string-width calculation
		if (!grapheme) continue;

		const graphemeWidth = visibleWidth(grapheme);

		if (currentWidth + graphemeWidth > targetWidth) {
			break;
		}

		result += grapheme;
		currentWidth += graphemeWidth;
	}

	// Add reset code before ellipsis to prevent styling leaking into it
	const truncated = `${result}\x1b[0m${ellipsis}`;
	if (pad) {
		const truncatedWidth = visibleWidth(truncated);
		return truncated + " ".repeat(Math.max(0, maxWidth - truncatedWidth));
	}
	return truncated;
}

/**
 * Extract a range of visible columns from a line. Handles ANSI codes and wide chars.
 * @param strict - If true, exclude wide chars at boundary that would extend past the range
 */
export function sliceByColumn(line: string, startCol: number, length: number, strict = false): string {
	return sliceWithWidth(line, startCol, length, strict).text;
}

/** Like sliceByColumn but also returns the actual visible width of the result. */
export function sliceWithWidth(
	line: string,
	startCol: number,
	length: number,
	strict = false,
): { text: string; width: number } {
	if (length <= 0) return { text: "", width: 0 };
	const endCol = startCol + length;
	let result = "",
		resultWidth = 0,
		currentCol = 0,
		i = 0,
		pendingAnsi = "";

	while (i < line.length) {
		const ansi = extractAnsiCode(line, i);
		if (ansi) {
			if (currentCol >= startCol && currentCol < endCol) result += ansi.code;
			else if (currentCol < startCol) pendingAnsi += ansi.code;
			i += ansi.length;
			continue;
		}

		let textEnd = i;
		while (textEnd < line.length && !extractAnsiCode(line, textEnd)) textEnd++;

		for (const { segment } of segmenter.segment(line.slice(i, textEnd))) {
			const w = visibleWidth(segment);
			const inRange = currentCol >= startCol && currentCol < endCol;
			const fits = !strict || currentCol + w <= endCol;
			if (inRange && fits) {
				if (pendingAnsi) {
					result += pendingAnsi;
					pendingAnsi = "";
				}
				result += segment;
				resultWidth += w;
			}
			currentCol += w;
			if (currentCol >= endCol) break;
		}
		i = textEnd;
		if (currentCol >= endCol) break;
	}
	return { text: result, width: resultWidth };
}

// Pooled tracker instance for extractSegments (avoids allocation per call)
const pooledStyleTracker = new AnsiCodeTracker();

/**
 * Extract "before" and "after" segments from a line in a single pass.
 * Used for overlay compositing where we need content before and after the overlay region.
 * Preserves styling from before the overlay that should affect content after it.
 */
export function extractSegments(
	line: string,
	beforeEnd: number,
	afterStart: number,
	afterLen: number,
	strictAfter = false,
): { before: string; beforeWidth: number; after: string; afterWidth: number } {
	let before = "",
		beforeWidth = 0,
		after = "",
		afterWidth = 0;
	let currentCol = 0,
		i = 0;
	let pendingAnsiBefore = "";
	let afterStarted = false;
	const afterEnd = afterStart + afterLen;

	// Track styling state so "after" inherits styling from before the overlay
	pooledStyleTracker.clear();

	while (i < line.length) {
		const ansi = extractAnsiCode(line, i);
		if (ansi) {
			// Track all SGR codes to know styling state at afterStart
			pooledStyleTracker.process(ansi.code);
			// Include ANSI codes in their respective segments
			if (currentCol < beforeEnd) {
				pendingAnsiBefore += ansi.code;
			} else if (currentCol >= afterStart && currentCol < afterEnd && afterStarted) {
				// Only include after we've started "after" (styling already prepended)
				after += ansi.code;
			}
			i += ansi.length;
			continue;
		}

		let textEnd = i;
		while (textEnd < line.length && !extractAnsiCode(line, textEnd)) textEnd++;

		for (const { segment } of segmenter.segment(line.slice(i, textEnd))) {
			const w = visibleWidth(segment);

			if (currentCol < beforeEnd) {
				if (pendingAnsiBefore) {
					before += pendingAnsiBefore;
					pendingAnsiBefore = "";
				}
				before += segment;
				beforeWidth += w;
			} else if (currentCol >= afterStart && currentCol < afterEnd) {
				const fits = !strictAfter || currentCol + w <= afterEnd;
				if (fits) {
					// On first "after" grapheme, prepend inherited styling from before overlay
					if (!afterStarted) {
						after += pooledStyleTracker.getActiveCodes();
						afterStarted = true;
					}
					after += segment;
					afterWidth += w;
				}
			}

			currentCol += w;
			// Early exit: done with "before" only, or done with both segments
			if (afterLen <= 0 ? currentCol >= beforeEnd : currentCol >= afterEnd) break;
		}
		i = textEnd;
		if (afterLen <= 0 ? currentCol >= beforeEnd : currentCol >= afterEnd) break;
	}

	return { before, beforeWidth, after, afterWidth };
}