// --- `sl` Command Implementation ---

import type { Item } from "../fs/Item"
import type { SimpleStream } from "../utils/SimpleStream"
import { Program } from "./Program"

export class Sl extends Program {
    // The classic D51 locomotive ASCII art with 3 frames of wheel animation.
    // Notice the trailing space on each line: this acts as an automatic "eraser"
    // for the previous frame as the train moves left!
    private static readonly D51_FRAMES: string[][] = [
        [
            '      ====        ________                ___________ ',
            '  _D _|  |_______/        \\__I_I_____===__|_________| ',
            '   |(_)---  |   H\\________/ |   |        =|___ ___|   ',
            '   /     |  |   H  |  |     |   |         ||_| |_||   ',
            '  |      |  |   H  |__--------------------| [___] |   ',
            '  | ________|___H__/__|_____/[][]~\\_______|       |   ',
            '  |/ |   |-----------I_____I [][] []  D   |=======|   ',
            '__/ =| o |=-O=====O=====O=====O \\ ____Y___________|   ',
            ' |/-=|___|=    ||    ||    ||    |_____/~\\___/        ',
            '  \\_/      \\__/  \\__/  \\__/  \\__/      \\_/            ',
        ],
        [
            '      ====        ________                ___________ ',
            '  _D _|  |_______/        \\__I_I_____===__|_________| ',
            '   |(_)---  |   H\\________/ |   |        =|___ ___|   ',
            '   /     |  |   H  |  |     |   |         ||_| |_||   ',
            '  |      |  |   H  |__--------------------| [___] |   ',
            '  | ________|___H__/__|_____/[][]~\\_______|       |   ',
            '  |/ |   |-----------I_____I [][] []  D   |=======|   ',
            '__/ =| o |=-~O====O====O====O~  \\ ____Y___________|   ',
            ' |/-=|___|=    ||    ||    ||    |_____/~\\___/        ',
            '  \\_/      \\__/  \\__/  \\__/  \\__/      \\_/            ',
        ],
        [
            '      ====        ________                ___________ ',
            '  _D _|  |_______/        \\__I_I_____===__|_________| ',
            '   |(_)---  |   H\\________/ |   |        =|___ ___|   ',
            '   /     |  |   H  |  |     |   |         ||_| |_||   ',
            '  |      |  |   H  |__--------------------| [___] |   ',
            '  | ________|___H__/__|_____/[][]~\\_______|       |   ',
            '  |/ |   |-----------I_____I [][] []  D   |=======|   ',
            '__/ =| o |=-~~O===O===O===O~~   \\ ____Y___________|   ',
            ' |/-=|___|=    ||    ||    ||    |_____/~\\___/        ',
            '  \\_/      \\__/  \\__/  \\__/  \\__/      \\_/            ',
        ],
    ]

    public async Exec(
        _: SimpleStream<string>,
        stdout: SimpleStream<string>,
        __: Item,
        args: string[],
    ): Promise<number> {
        // Original `sl` behavior flags
        const isFly = args.includes('-F')

        // Terminal size assumptions since they aren't provided by the API
        const termWidth = 100
        const trainWidth = Sl.D51_FRAMES[0][0].length

        // The train starts off-screen to the right and ends completely off-screen to the left
        const startX = termWidth
        const endX = -trainWidth

        // Clear screen (new page using form feed)
        stdout.emit('\f')

        let frameIdx = 0
        for (let x = startX; x >= endX; x--) {
            const frame = Sl.D51_FRAMES[frameIdx % Sl.D51_FRAMES.length]

            // If the `-F` flag is passed, the train "flies" upwards as it moves forward
            let startY = isFly ? Math.floor(x / 4) + 2 : 5

            for (let y = 0; y < frame.length; y++) {
                const line = frame[y]
                let outLine = line
                let cursorX = x

                // When the train hits the left edge, we must truncate the string
                // and lock the drawing cursor to X=0 to prevent terminal wrapping artifacts
                if (x < 0) {
                    cursorX = 0
                    outLine = line.substring(-x)
                }

                const cursorY = startY + y

                // Only render if within vertical bounds and there's text left to draw
                if (cursorY >= 0 && outLine.length > 0) {
                    // Send absolute cursor positioning sequence
                    stdout.emit(`\0cma;${cursorX};${cursorY}\0`)
                    // Render the frame line
                    stdout.emit(outLine)
                }
            }

            // Artificial delay to pace the animation
            await this.sleep(40)
            frameIdx++

            console.log(frameIdx)
        }

        // Return the cursor back to a safe position to give shell control back seamlessly
        stdout.emit(`\0cma;0;20\0\n`)

        return 0 // POSIX successful exit code
    }

    /**
     * Utility method to pause execution to pace the animation frames.
     */
    private sleep(ms: number): Promise<void> {
        return new Promise(resolve => setTimeout(resolve, ms))
    }
}