// Shared text selection helpers for acme-style double-click behavior.
// Brackets select their nested content; quotes select by parity.

function isQuote(ch) {
    return ch === "'" || ch === '"' || ch === '`'
}

// A quote at position qPos opens a pair when an even number of identical
// quote chars precede it; odd means it closes one.
function quoteIsOpener(text, qPos, quote) {
    var count = 0
    for (var c = 0; c < qPos; c++) {
        if (text.charAt(c) === quote) count++
    }
    return (count % 2) === 0
}

function findQuoteForward(text, qPos, quote) {
    for (var c = qPos + 1; c < text.length; c++) {
        if (text.charAt(c) === quote) return c
    }
    return -1
}

function findQuoteBackward(text, qPos, quote) {
    for (var c = qPos - 1; c >= 0; c--) {
        if (text.charAt(c) === quote) return c
    }
    return -1
}

function matchingBracket(ch) {
    switch (ch) {
    case '(': return {match: ')', isOpener: true}
    case '[': return {match: ']', isOpener: true}
    case '{': return {match: '}', isOpener: true}
    case ')': return {match: '(', isOpener: false}
    case ']': return {match: '[', isOpener: false}
    case '}': return {match: '{', isOpener: false}
    default: return null
    }
}

function findCloser(text, startPos, opener, closer) {
    var depth = 1
    var pos = startPos
    while (pos < text.length) {
        var ch = text.charAt(pos)
        if (ch === opener) depth++
        else if (ch === closer) {
            depth--
            if (depth === 0) return pos
        }
        pos++
    }
    return -1
}

function findOpener(text, startPos, opener, closer) {
    var depth = 1
    var pos = startPos
    while (pos >= 0) {
        var ch = text.charAt(pos)
        if (ch === closer) depth++
        else if (ch === opener) {
            depth--
            if (depth === 0) return pos
        }
        pos--
    }
    return -1
}

// Select text between a matching delimiter pair on double-click.
// Returns true if a pair was found and the inner content selected.
function selectBracketPair(textEdit, mouseX, mouseY) {
    var cursorPos = textEdit.positionAt(mouseX, mouseY)
    var text = textEdit.getText(0, textEdit.length)

    if (cursorPos < 0 || cursorPos > text.length) return false

    var rightCh = cursorPos < text.length ? text.charAt(cursorPos) : ''
    var leftCh = cursorPos > 0 ? text.charAt(cursorPos - 1) : ''

    // Quote pairs first.
    var q = ''
    var qPos = -1
    if (isQuote(rightCh)) {
        q = rightCh
        qPos = cursorPos
    } else if (isQuote(leftCh)) {
        q = leftCh
        qPos = cursorPos - 1
    }
    if (q !== '') {
        var qOpen = -1
        var qClose = -1
        if (quoteIsOpener(text, qPos, q)) {
            qOpen = qPos
            qClose = findQuoteForward(text, qPos, q)
        } else {
            qClose = qPos
            qOpen = findQuoteBackward(text, qPos, q)
        }
        if (qOpen < 0 || qClose < 0) return false
        textEdit.select(qOpen + 1, qClose)
        return true
    }

    // Bracket pairs.
    var rightMatch = matchingBracket(rightCh)
    var leftMatch = matchingBracket(leftCh)

    var innerStart = -1
    var innerEnd = -1

    if (rightMatch && rightMatch.isOpener) {
        var closerPos = findCloser(text, cursorPos + 1, rightCh, rightMatch.match)
        if (closerPos >= 0) {
            innerStart = cursorPos + 1
            innerEnd = closerPos
        }
    } else if (leftMatch && !leftMatch.isOpener) {
        var openerPos = findOpener(text, cursorPos - 2, leftMatch.match, leftCh)
        if (openerPos >= 0) {
            innerStart = openerPos + 1
            innerEnd = cursorPos - 1
        }
    } else if (rightMatch && !rightMatch.isOpener) {
        var openerPos2 = findOpener(text, cursorPos - 1, rightMatch.match, rightCh)
        if (openerPos2 >= 0) {
            innerStart = openerPos2 + 1
            innerEnd = cursorPos
        }
    } else if (leftMatch && leftMatch.isOpener) {
        var closerPos2 = findCloser(text, cursorPos, leftCh, leftMatch.match)
        if (closerPos2 >= 0) {
            innerStart = cursorPos
            innerEnd = closerPos2
        }
    }

    if (innerStart >= 0 && innerEnd >= innerStart) {
        textEdit.select(innerStart, innerEnd)
        return true
    }
    return false
}

// Select the plain word under the mouse (double-click word select).
function selectWordAt(textEdit, mouseX, mouseY) {
    var cursorPos = textEdit.positionAt(mouseX, mouseY)
    var text = textEdit.getText(0, textEdit.length)
    if (cursorPos < 0 || cursorPos > text.length) return

    function isword(ch) {
        return /[A-Za-z0-9_]/.test(ch)
    }

    var start = cursorPos
    while (start > 0 && isword(text.charAt(start - 1))) start--
    var end = cursorPos
    while (end < text.length && isword(text.charAt(end))) end++

    if (start === end) return
    textEdit.select(start, end)
}