import assert from "assert"
import { normalize as normalizeOptions, Options } from "./options"

interface Position {
    line: number;
    column: number;
}

type Pos = Position

// Goals:
// 1. Minimize new string creation.
// 2. Keep (de)identation O(lines) time.
// 3. Permit negative indentations.
// 4. Enforce immutability.
// 5. No newline characters.

type LineInfo = {
    readonly line: string;
    readonly indent: number;
    readonly locked: boolean;
    readonly sliceStart: number;
    readonly sliceEnd: number;
}

export class Lines {
    public readonly length: number;
    public readonly name: string | null;
    private cachedTabWidth: number | void = void 0;

    constructor(
        private infos: LineInfo[],
        sourceFileName: string | null = null,
    ) {
        assert.ok(infos.length > 0)
        this.length = infos.length
        this.name = sourceFileName || null
    }

    toString(options?: Options) {
        return this.sliceString(this.firstPos(), this.lastPos(), options)
    }

    bootstrapCharAt(pos: Pos) {
        assert.strictEqual(typeof pos, "object")
        assert.strictEqual(typeof pos.line, "number")
        assert.strictEqual(typeof pos.column, "number")

        const line = pos.line, column = pos.column, strings = this.toString().split(lineTerminatorSeqExp), string = strings[line - 1]

        if (typeof string === "undefined")
            return ""

        if (column === string.length &&
            line < strings.length)
            return "\n"

        if (column >= string.length)
            return ""

        return string.charAt(column)
    }

    charAt(pos: Pos) {
        assert.strictEqual(typeof pos, "object")
        assert.strictEqual(typeof pos.line, "number")
        assert.strictEqual(typeof pos.column, "number")

        let line = pos.line, column = pos.column, secret = this, infos = secret.infos, info = infos[line - 1], c = column

        if (typeof info === "undefined" || c < 0)
            return ""

        const indent = this.getIndentAt(line)
        if (c < indent)
            return " "

        c += info.sliceStart - indent

        if (c === info.sliceEnd &&
            line < this.length)
            return "\n"

        if (c >= info.sliceEnd)
            return ""

        return info.line.charAt(c)
    }

    stripMargin(width: number, skipFirstLine: boolean) {
        if (width === 0)
            return this

        assert.ok(width > 0, "negative margin: " + width)

        if (skipFirstLine && this.length === 1)
            return this

        const lines = new Lines(this.infos.map(function (info: any, i: any) {
            if (info.line && (i > 0 || !skipFirstLine)) {
                info = {
                    ...info,
                    indent: Math.max(0, info.indent - width),
                }
            }
            return info
        }))

        return lines
    }

    indent(by: number) {
        if (by === 0) {
            return this
        }

        const lines = new Lines(this.infos.map(function (info: any) {
            if (info.line && !info.locked) {
                info = {
                    ...info,
                    indent: info.indent + by,
                }
            }
            return info
        }))

        return lines
    }

    indentTail(by: number) {
        if (by === 0) {
            return this
        }

        if (this.length < 2) {
            return this
        }

        const lines = new Lines(this.infos.map(function (info: any, i: any) {
            if (i > 0 && info.line && !info.locked) {
                info = {
                    ...info,
                    indent: info.indent + by,
                }
            }

            return info
        }))

        return lines
    }

    lockIndentTail() {
        if (this.length < 2) {
            return this
        }

        return new Lines(this.infos.map((info: any, i: any) => ({
            ...info,
            locked: i > 0
        })))
    }

    getIndentAt(line: number) {
        assert.ok(line >= 1, "no line " + line + " (line numbers start from 1)")
        return Math.max(this.infos[line - 1].indent, 0)
    }

    guessTabWidth() {
        if (typeof this.cachedTabWidth === "number") {
            return this.cachedTabWidth
        }

        const counts: any[] = [] // Sparse array.
        let lastIndent = 0

        for (let line = 1, last = this.length; line <= last; ++line) {
            const info = this.infos[line - 1]
            const sliced = info.line.slice(info.sliceStart, info.sliceEnd)

            // Whitespace-only lines don't tell us much about the likely tab
            // width of this code.
            if (isOnlyWhitespace(sliced)) {
                continue
            }

            const diff = Math.abs(info.indent - lastIndent)
            counts[diff] = ~~counts[diff] + 1
            lastIndent = info.indent
        }

        let maxCount = -1
        let result = 2

        for (let tabWidth = 1;
            tabWidth < counts.length;
            tabWidth += 1) {
            if (hasOwn.call(counts, tabWidth) &&
                counts[tabWidth] > maxCount) {
                maxCount = counts[tabWidth]
                result = tabWidth
            }
        }

        return this.cachedTabWidth = result
    }

    // Determine if the list of lines has a first line that starts with a //
    // or /* comment. If this is the case, the code may need to be wrapped in
    // parens to avoid ASI issues.
    startsWithComment() {
        if (this.infos.length === 0) {
            return false
        }
        const firstLineInfo = this.infos[0], sliceStart = firstLineInfo.sliceStart, sliceEnd = firstLineInfo.sliceEnd, firstLine = firstLineInfo.line.slice(sliceStart, sliceEnd).trim()
        return firstLine.length === 0 ||
            firstLine.slice(0, 2) === "//" ||
            firstLine.slice(0, 2) === "/*"
    }

    isOnlyWhitespace() {
        return isOnlyWhitespace(this.toString())
    }

    isPrecededOnlyByWhitespace(pos: Pos) {
        const info = this.infos[pos.line - 1]
        const indent = Math.max(info.indent, 0)

        const diff = pos.column - indent
        if (diff <= 0) {
            // If pos.column does not exceed the indentation amount, then
            // there must be only whitespace before it.
            return true
        }

        const start = info.sliceStart
        const end = Math.min(start + diff, info.sliceEnd)
        const prefix = info.line.slice(start, end)

        return isOnlyWhitespace(prefix)
    }

    getLineLength(line: number) {
        const info = this.infos[line - 1]
        return this.getIndentAt(line) + info.sliceEnd - info.sliceStart
    }

    nextPos(pos: Pos, skipSpaces: boolean = false) {
        const l = Math.max(pos.line, 0), c = Math.max(pos.column, 0)

        if (c < this.getLineLength(l)) {
            pos.column += 1

            return skipSpaces
                ? !!this.skipSpaces(pos, false, true)
                : true
        }

        if (l < this.length) {
            pos.line += 1
            pos.column = 0

            return skipSpaces
                ? !!this.skipSpaces(pos, false, true)
                : true
        }

        return false
    }

    prevPos(pos: Pos, skipSpaces: boolean = false) {
        let l = pos.line, c = pos.column

        if (c < 1) {
            l -= 1

            if (l < 1)
                return false

            c = this.getLineLength(l)

        } else {
            c = Math.min(c - 1, this.getLineLength(l))
        }

        pos.line = l
        pos.column = c

        return skipSpaces
            ? !!this.skipSpaces(pos, true, true)
            : true
    }

    firstPos() {
        // Trivial, but provided for completeness.
        return { line: 1, column: 0 }
    }

    lastPos() {
        return {
            line: this.length,
            column: this.getLineLength(this.length)
        }
    }

    skipSpaces(
        pos: Pos,
        backward: boolean = false,
        modifyInPlace: boolean = false,
    ) {
        if (pos) {
            pos = modifyInPlace ? pos : {
                line: pos.line,
                column: pos.column
            }
        } else if (backward) {
            pos = this.lastPos()
        } else {
            pos = this.firstPos()
        }

        if (backward) {
            while (this.prevPos(pos)) {
                if (!isOnlyWhitespace(this.charAt(pos)) &&
                    this.nextPos(pos)) {
                    return pos
                }
            }

            return null

        } else {
            while (isOnlyWhitespace(this.charAt(pos))) {
                if (!this.nextPos(pos)) {
                    return null
                }
            }

            return pos
        }
    }

    trimLeft() {
        const pos = this.skipSpaces(this.firstPos(), false, true)
        return pos ? this.slice(pos) : emptyLines
    }

    trimRight() {
        const pos = this.skipSpaces(this.lastPos(), true, true)
        return pos ? this.slice(this.firstPos(), pos) : emptyLines
    }

    trim() {
        const start = this.skipSpaces(this.firstPos(), false, true)
        if (start === null) {
            return emptyLines
        }

        const end = this.skipSpaces(this.lastPos(), true, true)
        if (end === null) {
            return emptyLines
        }

        return this.slice(start, end)
    }

    eachPos(
        callback: (pos: Pos) => any,
        startPos: Pos = this.firstPos(),
        skipSpaces: boolean = false,
    ) {
        var pos = this.firstPos()

        if (startPos) {
            pos.line = startPos.line
            pos.column = startPos.column
        }

        if (skipSpaces && !this.skipSpaces(pos, false, true)) {
            return // Encountered nothing but spaces.
        }

        do callback.call(this, pos)
        while (this.nextPos(pos, skipSpaces))
    }

    bootstrapSlice(start: Pos, end: Pos) {
        const strings = this.toString().split(
            lineTerminatorSeqExp
        ).slice(
            start.line - 1,
            end.line
        )

        if (strings.length > 0) {
            strings.push(strings.pop()!.slice(0, end.column))
            strings[0] = strings[0].slice(start.column)
        }

        return fromString(strings.join("\n"))
    }

    slice(start?: Pos, end?: Pos) {
        if (!end) {
            if (!start) {
                // The client seems to want a copy of this Lines object, but
                // Lines objects are immutable, so it's perfectly adequate to
                // return the same object.
                return this
            }

            // Slice to the end if no end position was provided.
            end = this.lastPos()
        }

        if (!start) {
            throw new Error("cannot slice with end but not start")
        }

        const sliced = this.infos.slice(start.line - 1, end.line)

        if (start.line === end.line) {
            sliced[0] = sliceInfo(sliced[0], start.column, end.column)
        } else {
            assert.ok(start.line < end.line)
            sliced[0] = sliceInfo(sliced[0], start.column)
            sliced.push(sliceInfo(sliced.pop(), 0, end.column))
        }

        const lines = new Lines(sliced)

        return lines
    }

    bootstrapSliceString(start: Pos, end: Pos, options?: Options) {
        return this.slice(start, end).toString(options)
    }

    sliceString(
        start: Pos = this.firstPos(),
        end: Pos = this.lastPos(),
        options?: Options,
    ) {
        options = normalizeOptions(options)

        const parts = []
        const { tabWidth = 2 } = options

        for (let line = start.line; line <= end.line; ++line) {
            let info = this.infos[line - 1]

            if (line === start.line) {
                if (line === end.line) {
                    info = sliceInfo(info, start.column, end.column)
                } else {
                    info = sliceInfo(info, start.column)
                }
            } else if (line === end.line) {
                info = sliceInfo(info, 0, end.column)
            }

            const indent = Math.max(info.indent, 0)

            const before = info.line.slice(0, info.sliceStart)
            if (options.reuseWhitespace &&
                isOnlyWhitespace(before) &&
                countSpaces(before, options.tabWidth) === indent) {
                // Reuse original spaces if the indentation is correct.
                parts.push(info.line.slice(0, info.sliceEnd))
                continue
            }

            let tabs = 0
            let spaces = indent

            if (options.useTabs) {
                tabs = Math.floor(indent / tabWidth)
                spaces -= tabs * tabWidth
            }

            let result = ""

            if (tabs > 0) {
                result += new Array(tabs + 1).join("\t")
            }

            if (spaces > 0) {
                result += new Array(spaces + 1).join(" ")
            }

            result += info.line.slice(info.sliceStart, info.sliceEnd)

            parts.push(result)
        }

        return parts.join(options.lineTerminator)
    }

    isEmpty() {
        return this.length < 2 && this.getLineLength(1) < 1
    }

    join(elements: (string | Lines)[]) {
        const separator = this
        const infos: any[] = []
        let prevInfo: any

        function appendLines(linesOrNull: Lines | null) {
            if (linesOrNull === null) {
                return
            }

            if (prevInfo) {
                const info = linesOrNull.infos[0]
                const indent = new Array(info.indent + 1).join(" ")

                prevInfo.line = prevInfo.line.slice(0, prevInfo.sliceEnd) + indent + info.line.slice(info.sliceStart, info.sliceEnd)

                // If any part of a line is indentation-locked, the whole line
                // will be indentation-locked.
                prevInfo.locked = prevInfo.locked || info.locked

                prevInfo.sliceEnd = prevInfo.line.length

            }

            linesOrNull.infos.forEach(function (info: any, i: any) {
                if (!prevInfo || i > 0) {
                    prevInfo = { ...info }
                    infos.push(prevInfo)
                }
            })
        }

        function appendWithSeparator(linesOrNull: Lines | null, i: number) {
            if (i > 0)
                appendLines(separator)
            appendLines(linesOrNull)
        }

        elements.map(function (elem: any) {
            const lines = fromString(elem)
            if (lines.isEmpty())
                return null
            return lines
        }).forEach((linesOrNull, i) => {
            if (separator.isEmpty()) {
                appendLines(linesOrNull)
            } else {
                appendWithSeparator(linesOrNull, i)
            }
        })

        if (infos.length < 1)
            return emptyLines

        const lines = new Lines(infos)

        return lines
    }

    concat(...args: (string | Lines)[]) {
        const list: typeof args = [this]
        list.push.apply(list, args)
        assert.strictEqual(list.length, args.length + 1)
        return emptyLines.join(list)
    }
}

const fromStringCache: any = {}
var hasOwn = fromStringCache.hasOwnProperty
const maxCacheKeyLen = 10

export function countSpaces(spaces: any, tabWidth?: number) {
    let count = 0
    const len = spaces.length

    for (let i = 0; i < len; ++i) {
        switch (spaces.charCodeAt(i)) {
            case 9: // '\t'
                assert.strictEqual(typeof tabWidth, "number")
                assert.ok(tabWidth! > 0)

                var next = Math.ceil(count / tabWidth!) * tabWidth!
                if (next === count) {
                    count += tabWidth!
                } else {
                    count = next
                }

                break

            case 11: // '\v'
            case 12: // '\f'
            case 13: // '\r'
            case 0xfeff: // zero-width non-breaking space
                // These characters contribute nothing to indentation.
                break

            case 32: // ' '
            default: // Treat all other whitespace like ' '.
                count += 1
                break
        }
    }

    return count
}

const leadingSpaceExp = /^\s*/

// As specified here: http://www.ecma-international.org/ecma-262/6.0/#sec-line-terminators
var lineTerminatorSeqExp = /\r\n|\r(?!\n)|\n|\u2028|\u2029/

/**
 * @param {Object} options - Options object that configures printing.
 */
export function fromString(
    string: string | Lines,
    options?: Options,
): Lines {
    if (string instanceof Lines)
        return string

    string += ""

    const tabWidth = options && options.tabWidth
    const tabless = string.indexOf("\t") < 0
    const cacheable = !options && tabless && (string.length <= maxCacheKeyLen)

    assert.ok(tabWidth || tabless, "No tab width specified but encountered tabs in string\n" + string)

    if (cacheable && hasOwn.call(fromStringCache, string))
        return fromStringCache[string]

    const lines = new Lines(string.split(lineTerminatorSeqExp).map(function (line) {
        // TODO: handle null exec result
        const spaces = leadingSpaceExp.exec(line)![0]
        return {
            line: line,
            indent: countSpaces(spaces, tabWidth),
            // Boolean indicating whether this line can be reindented.
            locked: false,
            sliceStart: spaces.length,
            sliceEnd: line.length
        }
    }))

    if (cacheable)
        fromStringCache[string] = lines

    return lines
}

function isOnlyWhitespace(string: string) {
    return !/\S/.test(string)
}

function sliceInfo(info: any, startCol: number, endCol?: number) {
    let sliceStart = info.sliceStart
    let sliceEnd = info.sliceEnd
    let indent = Math.max(info.indent, 0)
    let lineLength = indent + sliceEnd - sliceStart

    if (typeof endCol === "undefined") {
        endCol = lineLength
    }

    startCol = Math.max(startCol, 0)
    endCol = Math.min(endCol, lineLength)
    endCol = Math.max(endCol, startCol)

    if (endCol < indent) {
        indent = endCol
        sliceEnd = sliceStart
    } else {
        sliceEnd -= lineLength - endCol
    }

    lineLength = endCol
    lineLength -= startCol

    if (startCol < indent) {
        indent -= startCol
    } else {
        startCol -= indent
        indent = 0
        sliceStart += startCol
    }

    assert.ok(indent >= 0)
    assert.ok(sliceStart <= sliceEnd)
    assert.strictEqual(lineLength, indent + sliceEnd - sliceStart)

    if (info.indent === indent &&
        info.sliceStart === sliceStart &&
        info.sliceEnd === sliceEnd) {
        return info
    }

    return {
        line: info.line,
        indent: indent,
        // A destructive slice always unlocks indentation.
        locked: false,
        sliceStart: sliceStart,
        sliceEnd: sliceEnd
    }
}

export function concat(elements: any) {
    return emptyLines.join(elements)
}

// The emptyLines object needs to be created all the way down here so that
// Lines.prototype will be fully populated.
const emptyLines = fromString("")