import emojiRegex from 'emoji-regex'

import { eastAsianWidth } from 'get-east-asian-width'

import stripAnsi from 'strip-ansi'

import { getGraphemeSegmenter } from '../utils/intl.js'

const EMOJI_REGEX = emojiRegex()

/**

* Fallback JavaScript implementation of stringWidth when Bun.stringWidth is not available.

*

* Get the display width of a string as it would appear in a terminal.

*

* This is a more accurate alternative to the string-width package that correctly handles

* characters like ⚠ (U+26A0) which string-width incorrectly reports as width 2.

*

* The implementation uses eastAsianWidth directly with ambiguousAsWide: false,

* which correctly treats ambiguous-width characters as narrow (width 1) as

* recommended by the Unicode standard for Western contexts.

*/

function stringWidthJavaScript(str: string): number {

if (typeof str !== 'string' || str.length === 0) {

return 0

}

// Fast path: pure ASCII string (no ANSI codes, no wide chars)

let isPureAscii = true

for (let i = 0; i < str.length; i++) {

const code = str.charCodeAt(i)

// Check for non-ASCII or ANSI escape (0x1b)

if (code >= 127 || code === 0x1b) {

isPureAscii = false

break

}

}

if (isPureAscii) {

// Count printable characters (exclude control chars)

let width = 0

for (let i = 0; i < str.length; i++) {

const code = str.charCodeAt(i)

if (code > 0x1f) {

width++

}

}

return width

}

// Strip ANSI if escape character is present

if (str.includes('\x1b')) {

str = stripAnsi(str)

if (str.length === 0) {

return 0

}

}

// Fast path: simple Unicode (no emoji, variation selectors, or joiners)

if (!needsSegmentation(str)) {

let width = 0

for (const char of str) {

const codePoint = char.codePointAt(0)!

if (!isZeroWidth(codePoint)) {

width += eastAsianWidth(codePoint, { ambiguousAsWide: false })

}

}

return width

}

let width = 0

for (const { segment: grapheme } of getGraphemeSegmenter().segment(str)) {

// Check for emoji first (most emoji sequences are width 2)

EMOJI_REGEX.lastIndex = 0

if (EMOJI_REGEX.test(grapheme)) {

width += getEmojiWidth(grapheme)

continue

}

// Calculate width for non-emoji graphemes

// For grapheme clusters (like Devanagari conjuncts with virama+ZWJ), only count

// the first non-zero-width character's width since the cluster renders as one glyph

for (const char of grapheme) {

const codePoint = char.codePointAt(0)!

if (!isZeroWidth(codePoint)) {

width += eastAsianWidth(codePoint, { ambiguousAsWide: false })

break

}

}

}

return width

}

function needsSegmentation(str: string): boolean {

for (const char of str) {

const cp = char.codePointAt(0)!

// Emoji ranges

if (cp >= 0x1f300 && cp <= 0x1faff) return true

if (cp >= 0x2600 && cp <= 0x27bf) return true

if (cp >= 0x1f1e6 && cp <= 0x1f1ff) return true

// Variation selectors, ZWJ

if (cp >= 0xfe00 && cp <= 0xfe0f) return true

if (cp === 0x200d) return true

}

return false

}

function getEmojiWidth(grapheme: string): number {

// Regional indicators: single = 1, pair = 2

const first = grapheme.codePointAt(0)!

if (first >= 0x1f1e6 && first <= 0x1f1ff) {

let count = 0

for (const _ of grapheme) count++

return count === 1 ? 1 : 2

}

// Incomplete keycap: digit/symbol + VS16 without U+20E3

if (grapheme.length === 2) {

const second = grapheme.codePointAt(1)

if (

second === 0xfe0f &&

((first >= 0x30 && first <= 0x39) || first === 0x23 || first === 0x2a)

) {

return 1

}

}

return 2

}

function isZeroWidth(codePoint: number): boolean {

// Fast path for common printable range

if (codePoint >= 0x20 && codePoint < 0x7f) return false

if (codePoint >= 0xa0 && codePoint < 0x0300) return codePoint === 0x00ad

// Control characters

if (codePoint <= 0x1f || (codePoint >= 0x7f && codePoint <= 0x9f)) return true

// Zero-width and invisible characters

if (

(codePoint >= 0x200b && codePoint <= 0x200d) || // ZW space/joiner

codePoint === 0xfeff || // BOM

(codePoint >= 0x2060 && codePoint <= 0x2064) // Word joiner etc.

) {

return true

}

// Variation selectors

if (

(codePoint >= 0xfe00 && codePoint <= 0xfe0f) ||

(codePoint >= 0xe0100 && codePoint <= 0xe01ef)

) {

return true

}

// Combining diacritical marks

if (

(codePoint >= 0x0300 && codePoint <= 0x036f) ||

(codePoint >= 0x1ab0 && codePoint <= 0x1aff) ||

(codePoint >= 0x1dc0 && codePoint <= 0x1dff) ||

(codePoint >= 0x20d0 && codePoint <= 0x20ff) ||

(codePoint >= 0xfe20 && codePoint <= 0xfe2f)

) {

return true

}

// Indic script combining marks (covers Devanagari through Malayalam)

if (codePoint >= 0x0900 && codePoint <= 0x0d4f) {

// Signs and vowel marks at start of each script block

const offset = codePoint & 0x7f

if (offset <= 0x03) return true // Signs at block start

if (offset >= 0x3a && offset <= 0x4f) return true // Vowel signs, virama

if (offset >= 0x51 && offset <= 0x57) return true // Stress signs

if (offset >= 0x62 && offset <= 0x63) return true // Vowel signs

}

// Thai/Lao combining marks

// Note: U+0E32 (SARA AA), U+0E33 (SARA AM), U+0EB2, U+0EB3 are spacing vowels (width 1), not combining marks

if (

codePoint === 0x0e31 || // Thai MAI HAN-AKAT

(codePoint >= 0x0e34 && codePoint <= 0x0e3a) || // Thai vowel signs (skip U+0E32, U+0E33)

(codePoint >= 0x0e47 && codePoint <= 0x0e4e) || // Thai vowel signs and marks

codePoint === 0x0eb1 || // Lao MAI KAN

(codePoint >= 0x0eb4 && codePoint <= 0x0ebc) || // Lao vowel signs (skip U+0EB2, U+0EB3)

(codePoint >= 0x0ec8 && codePoint <= 0x0ecd) // Lao tone marks

) {

return true

}

// Arabic formatting

if (

(codePoint >= 0x0600 && codePoint <= 0x0605) ||

codePoint === 0x06dd ||

codePoint === 0x070f ||

codePoint === 0x08e2

) {

return true

}

// Surrogates, tag characters

if (codePoint >= 0xd800 && codePoint <= 0xdfff) return true

if (codePoint >= 0xe0000 && codePoint <= 0xe007f) return true

return false

}

// Note: complex-script graphemes like Devanagari क्ष (ka+virama+ZWJ+ssa) render

// as a single ligature glyph but occupy 2 terminal cells (wcwidth sums the base

// consonants). Bun.stringWidth=2 matches terminal cell allocation, which is what

// we need for cursor positioning — the JS fallback's grapheme-cluster width of 1

// would desync Ink's layout from the terminal.

//

// Bun.stringWidth is resolved once at module scope rather than checked on every

// call — typeof guards deopt property access and this is a hot path (~100k calls/frame).

const bunStringWidth =

typeof Bun !== 'undefined' && typeof Bun.stringWidth === 'function'

? Bun.stringWidth

: null

const BUN_STRING_WIDTH_OPTS = { ambiguousIsNarrow: true } as const

export const stringWidth: (str: string) => number = bunStringWidth

? str => bunStringWidth(str, BUN_STRING_WIDTH_OPTS)

: stringWidthJavaScript