// Web-Uno Shell
// the best name I could come up with lol

import { Clear } from '../../program/Clear'
import { Eval } from '../../program/Eval'
import { Loadprg } from '../../program/Loadprg'
import { Lsprg } from '../../program/Lsprg'
import { Info } from '../../program/Info'
import { Program } from '../../program/Program'
import { Terminal } from '../../terminal/Terminal'
import type { CursorPosition } from '../../terminal/CursorProperties'
import { EventBroadcaster } from '../../utils/EventBroadcaster'
import { SimpleStream } from '../../utils/SimpleStream'
import { Shell } from '../Shell'
import { Ls } from '../../program/Ls'
import { Item } from '../../fs/Item'
import { Touch } from '../../program/Touch'
import { Sl } from '../../program/Sl'
import { Rm } from '../../program/Rm'
import { Rl } from '../../program/Rl'
import { ResetIndexedDb } from '../../program/ResetIndexedDb'
import { Cat } from '../../program/Cat'
import { Echo } from '../../program/Echo'
import { Mkdir } from '../../program/Mkdir'
import { Cd } from '../../program/Cd'
import { Printf } from '../../program/Printf'
import { Pwd } from '../../program/Pwd'
import { Environment } from './Environment'
import { InputManager } from './InputManager'

export class Wush extends Shell {
    public readonly Version = "0.3.2"
    public readonly Name = "wush"

    // buffer
    _buffer: string[] = []
    _bufferPos: number = 0
    _promptStart: CursorPosition = { col: 0, row: 0 }

    private inputManager: InputManager
    // @ts-ignore unused for now
    private environment: Environment

    // exec stuff
    /**
     * -1 if the exec is currently running and anything else when it's not
     */
    private execExitCode: number = 0

    // streams
    readonly stdin: SimpleStream<string>
    readonly stdout: SimpleStream<string>

    private programs: { [name: string]: Program } = {}
    private workingDirectory: Item = null as unknown as Item // workdir is initialized in Init so this should be safe

    constructor(broadcaster: EventBroadcaster, terminal: Terminal) {
        super(broadcaster, terminal)

        // create streams
        this.stdin = new SimpleStream<string>()
        this.stdout = new SimpleStream<string>()

        this.inputManager = new InputManager(this, broadcaster)
        this.environment = new Environment()
    }

    async Init() {
        // initialize keyboard listener
        this.inputManager.RegisterEvents()

        // load workdir
        this.workingDirectory = await Item.Root()

        // register streams
        this.stdout.on(data => this.WriteEscapedString(data))

        // load core programs
        this.programs['clear'] = new Clear()
        this.programs['eval'] = new Eval()
        this.programs['loadprg'] = new Loadprg(this)
        this.programs['lsprg'] = new Lsprg(this)
        this.programs['info'] = new Info()
        this.programs['ls'] = new Ls()
        this.programs['touch'] = new Touch()
        this.programs['sl'] = new Sl()
        this.programs['rm'] = new Rm()
        this.programs['rl'] = new Rl()
        this.programs['rsindb'] = new ResetIndexedDb()
        this.programs['cat'] = new Cat()
        this.programs['echo'] = new Echo()
        this.programs['mkdir'] = new Mkdir()
        this.programs['pwd'] = new Pwd()
        this.programs['cd'] = new Cd(this)
        this.programs['printf'] = new Printf()

        // initial prompt
        this.Prompt()
    }

    HasRunningProgram(): boolean {
        return this.execExitCode === -1
    }

    GetPrograms(): { [name: string]: Program } {
        return this.programs
    }

    LoadProgram(program: Program, name: string) {
        this.programs[name] = program
    }

    UnloadProgram(name: string) {
        delete this.programs[name]
    }

    GetExecExitCode(): number {
        return this.execExitCode
    }

    async ExecuteProgram(name: string, args: string[]): Promise<void> {
        return new Promise<void>(resolve => {
            this.programs[name].Exec(this.stdin, this.stdout, this.workingDirectory, args)
                .then(code => {
                    this.execExitCode = code != -1 ? code : -2
                    resolve()
                })
                .catch((e) => {
                    this.WriteEscapedString(`wush: command ${name} exited with the following exception\n`)
                    this.WriteEscapedString(`    | ${String(e)}\n`)
                    resolve()
                })
                .finally(() => {
                    // check if the exec actually exited with an exit code
                    // and if not, set it to -2 to indicate that it didn't exit with a valid code
                    if (this.execExitCode === -1)
                        this.execExitCode = -2

                    // this.terminal.Write(`The program exited with exit code ${this.execExitCode}.`)
                    resolve()
                })
        })
    }

    Prompt() {
        this.terminal.Write(`user in ${this.workingDirectory.GetPath()} -> `)
        this._promptStart = this.terminal.GetCursorPosition()
        this._buffer = []
        this._bufferPos = 0

        this.inputManager.historyIndex = null
        this.inputManager.historyDraft = ''
    }

    /**
     * Changes the working directory
     * @param directory the directory to enter into
     * @throws an error if the directory cannot be opened
     */
    async SetWorkingDirectory(directory: Item) {
        if (!(await directory.Exists()) || !directory.IsDirectory())
            throw new Error(`Directory  ${directory.GetPath()} doesn't exist`)

        this.workingDirectory = directory
    }

    WriteStdin(data: string) {
        this.stdin.emit(data)
    }

    WriteEscapedString(data: string) {
        let buffer = ''

        // write the buffer to screen
        const flush = () => {
            if (buffer.length === 0)
                return

            this.terminal.Write(buffer)
            buffer = ''
        }

        // process the string
        let i = 0
        while (i < data.length) {
            const char = data[i]

            // check for escape sequences
            if (char === '\x1b') {
                flush()

                const nextIndex = this.ProcessEscapeSequence(data, i)
                if (nextIndex !== null) {
                    i = nextIndex
                    continue
                }
            }

            // check for control codes
            if (char === '\f' || char === '\n') {
                flush()

                this.ProcessControlCode(char)
                i++

                continue
            }

            buffer += char
            i++
        }

        flush()
    }

    PushToBuffer(text: string) {
        text.split('').forEach(char => {
            this._buffer.splice(this._bufferPos, 0, char)
            this._bufferPos++
        })
    }

    RemoveCharFromBuffer(amount: number, index: number) {
        this._buffer.splice(index - amount, amount)
        this._bufferPos -= amount
    }

    MoveBufferPos(index: number, absolute: boolean = false) {
        this._bufferPos = Math.max(absolute ? index : this._bufferPos + index, 0)
    }

    FlushBuffer() {
        this._buffer = []
        this._bufferPos = 0
    }

    // takes the prompt buffer, parses it and executes the contents
    async ExecuteLineBuffer(data?: string) {
        type OperatorToken = '&&' | '||' | '|' | ';'
        type Token = { type: 'word'; value: string } | { type: 'operator'; value: OperatorToken }
        type ParsedCommand = {
            args: string[]
            stdin: null | SimpleStream<string>
            stdout: null | SimpleStream<string>
        }
        type ParsedPipeline = { commands: ParsedCommand[] }
        type ParsedListItem = { pipeline: ParsedPipeline; operator: '&&' | '||' | ';' | null }

        // splits the buffer into processable pieces (tokens)
        const tokenize = (text: string): { tokens: Token[]; error: string | null } => {
            const tokens: Token[] = []

            // state machine stuff
            let current = ''
            let wordStarted = false
            let inSingleQuote = false
            let inDoubleQuote = false
            let escapeNext = false

            /**
             * adds a new word to the token buffer
             */
            const pushWord = () => {
                if (!wordStarted)
                    return

                tokens.push({ type: 'word', value: current })

                // reset the state
                current = ''
                wordStarted = false
            }

            // iterates over the provided text buffer
            for (let i = 0; i < text.length; i++) {
                const char = text[i]

                if (escapeNext) {
                    current += char
                    escapeNext = false
                    wordStarted = true
                    continue
                }

                // process strict (single quote) strings
                if (inSingleQuote) {
                    if (char === "'") {
                        inSingleQuote = false
                        wordStarted = true
                    } else {
                        current += char
                        wordStarted = true
                    }

                    continue
                }

                // process classic (double quote) strings
                if (inDoubleQuote) {
                    if (char === '"') {
                        inDoubleQuote = false
                        wordStarted = true
                    } else if (char === '\\') {
                        if (i + 1 >= text.length)
                            return { tokens: [], error: 'unterminated escape sequence' }

                        current += text[i + 1]
                        i++
                        wordStarted = true
                    } else {
                        current += char
                        wordStarted = true
                    }

                    continue
                }

                // state checks

                // escapes
                if (char === '\\') {
                    escapeNext = true
                    wordStarted = true
                    continue
                }

                // single quote strings
                if (char === "'") {
                    inSingleQuote = true
                    wordStarted = true
                    continue
                }

                // double quote strings
                if (char === '"') {
                    inDoubleQuote = true
                    wordStarted = true
                    continue
                }

                if (char === ' ' || char === '\t') {
                    pushWord()
                    continue
                }

                if (char === '#') {
                    if (!wordStarted)
                        break

                    current += char
                    wordStarted = true
                    continue
                }

                if (char === ';') {
                    pushWord()
                    tokens.push({ type: 'operator', value: ';' })
                    continue
                }

                if (char === '|') {
                    pushWord()
                    if (text[i + 1] === '|') {
                        tokens.push({ type: 'operator', value: '||' })
                        i++
                    } else {
                        tokens.push({ type: 'operator', value: '|' })
                    }
                    continue
                }

                if (char === '&') {
                    if (text[i + 1] === '&') {
                        pushWord()
                        tokens.push({ type: 'operator', value: '&&' })
                        i++
                    } else {
                        current += char
                        wordStarted = true
                    }
                    continue
                }

                current += char
                wordStarted = true
            }

            if (escapeNext)
                return { tokens: [], error: 'unterminated escape sequence' }
            if (inSingleQuote)
                return { tokens: [], error: 'unterminated single quote' }
            if (inDoubleQuote)
                return { tokens: [], error: 'unterminated double quote' }

            pushWord()
            return { tokens, error: null }
        }

        // parse the tokens into a list of parsed commands and pipelines
        const parseTokens = (tokens: Token[]): { list: ParsedListItem[]; error: string | null } => {
            const list: ParsedListItem[] = []
            let currentArgs: string[] = []
            let currentPipeline: ParsedCommand[] = []
            let expectCommand = false

            const pushCommand = () => {
                if (currentArgs.length === 0)
                    return false

                currentPipeline.push({
                    args: currentArgs,
                    stdin: null,
                    stdout: null,
                })
                currentArgs = []
                return true
            }

            const pushPipeline = (operator: '&&' | '||' | ';' | null) => {
                if (currentPipeline.length === 0)
                    return false

                list.push({ pipeline: { commands: currentPipeline }, operator })
                currentPipeline = []
                return true
            }

            for (const token of tokens) {
                if (token.type === 'word') {
                    currentArgs.push(token.value)
                    expectCommand = false
                    continue
                }

                if (token.value === '|') {
                    if (!pushCommand())
                        return { list: [], error: 'unexpected "|" operator' }

                    expectCommand = true
                    continue
                }

                if (!pushCommand() || !pushPipeline(token.value))
                    return { list: [], error: `unexpected "${token.value}" operator` }

                expectCommand = true
            }

            if (expectCommand)
                return { list: [], error: 'unexpected end of input' }

            if (currentArgs.length > 0)
                pushCommand()

            if (currentPipeline.length > 0)
                pushPipeline(null)

            return { list, error: null }
        }

        // process the buffer
        let line: string
        if (data) {
            // data overrides the buffer
            this._buffer = data.split('')
            this._bufferPos = 0
            line = data
        } else {
            // use shell buffer if no arbitrary string was provided
            line = this._buffer.join('')
            this.FlushBuffer()
        }

        const { tokens, error } = tokenize(line)
        if (error) {
            this.terminal.Write(`wush: error: ${error}`)
            this.terminal.MoveCursor(0, 1, { x: true, y: false })

            this.Prompt()
            return
        }

        const { list, error: parseError } = parseTokens(tokens)
        if (parseError) {
            this.terminal.Write(`wush: error: ${parseError}`)
            this.terminal.MoveCursor(0, 1, { x: true, y: false })

            this.Prompt()
            return
        }

        if (list.length === 0) {
            this.Prompt()
            return
        }

        if (list.some(item => item.pipeline.commands.length > 1)) {
            this.terminal.Write(`wush: error: pipes are not supported yet`)
            this.terminal.MoveCursor(0, 1, { x: true, y: false })

            this.Prompt()
            return
        }

        for (const item of list) {
            const command = item.pipeline.commands[0]

            this.execExitCode = -1

            if (this.programs[command.args[0]] instanceof Program) {
                await this.ExecuteProgram(command.args[0], command.args)
            } else {
                this.execExitCode = 0

                // don't print anything if there are no arguments
                if (command.args[0].length !== 0) {
                    this.terminal.Write(`wush: error: unknown command: ${command.args[0]}.`)
                    this.terminal.MoveCursor(0, 1, { x: true, y: false })

                    this.execExitCode = 127
                }
            }
        }

        this.Prompt()
    }

    ProcessControlCode(code: string): boolean {
        switch (code) {
            case '\f':
                this.terminal.NewPage()
                return true
            case '\n':
                this.terminal.MoveCursor(0, 1, { x: true, y: false })
                return true
            default:
                return false
        }
    }

    ProcessEscapeSequence(data: string, index: number): number | null {
        if (data[index] !== '\x1b' || data[index + 1] !== '[')
            return null

        let i = index + 2
        let params = ''

        while (i < data.length) {
            const char = data[i]

            if ((char >= '0' && char <= '9') || char === ';') {
                params += char
                i++
                continue
            }

            this.ProcessCsiControlCode(char, params)
            return i + 1
        }

        return data.length
    }

    ProcessCsiControlCode(command: string, params: string): boolean {
        const values = params.length === 0
            ? []
            : params.split(';').map(value => Number.parseInt(value, 10))

        switch (command) {
            case 'H':
            case 'f': {
                const row = Number.isFinite(values[0]) ? values[0] : 1
                const col = Number.isFinite(values[1]) ? values[1] : 1

                this.terminal.SetCursorPosition(Math.max(col - 1, 0), Math.max(row - 1, 0))
                return true
            }
            case 'J': {
                this.terminal.NewPage()
                return true
            }
            default:
                return false
        }
    }

    private GetWrapWidth(): number {
        const width = Math.floor(this.terminal.GetWidthCells())
        if (!Number.isFinite(width) || width <= 0)
            return 1

        return Math.max(1, width)
    }

    private GetCursorPositionForBufferPos(pos: number): CursorPosition {
        const width = this.GetWrapWidth()
        const absoluteIndex = this._promptStart.col + Math.max(pos, 0)
        const rowOffset = Math.floor(absoluteIndex / width)
        const col = absoluteIndex % width

        return { row: this._promptStart.row + rowOffset, col }
    }

    _SyncCursorToBuffer() {
        const position = this.GetCursorPositionForBufferPos(this._bufferPos)
        this.terminal.SetCursorPosition(position.col, position.row)
    }

    private ClearBuffer() {
        if (this._buffer.length === 0)
            return

        if (this._bufferPos < this._buffer.length) {
            this._bufferPos = this._buffer.length
            this._SyncCursorToBuffer()
        }

        while (this._bufferPos > 0) {
            this.terminal.RemoveCell()
            this.RemoveCharFromBuffer(1, this._bufferPos)
            this._SyncCursorToBuffer()
        }
    }

    _InsertText(text: string) {
        if (text.length === 0)
            return

        for (const char of text) {
            this.terminal.InsertCell(char)
            this.PushToBuffer(char)
            this._SyncCursorToBuffer()
        }
    }

    _SetBuffer(text: string) {
        this.ClearBuffer()
        this._InsertText(text)
    }
}