TerminalUI-mirror/Sources/TerminalUI/Lowlevel.swift

//
//  File.swift
//  
//
//  Created by Chris Eidhof on 06.05.21.
//

import Darwin

// Taken from https://stackoverflow.com/questions/49748507/listening-to-stdin-in-swift
func enableRawMode(file: Int32) -> termios {
    var raw: termios = .init()
    tcgetattr(file, &raw)
    let original = raw
    raw.c_lflag &= ~(UInt(ECHO | ICANON))
    tcsetattr(file, TCSAFLUSH, &raw);
    return original
}


func clearScreen() {
    _write("\u{1b}[2J")
}

func move(to: Point) {
    _write("\u{1b}[\(to.y+1);\(to.x+1)H")
}


func setColor(foregroundColor: Color?, backgroundColor: Color?) {
    _write("\u{1b}[0m") // todo this is unnecessarily expensive
    if let f = foregroundColor {
        _write("\u{1b}[\(f.foreground)m")
    } else {
    }
    if let b = backgroundColor {
        _write("\u{1b}[\(b.background)m")
    }
}

func _write(_ str: String, fd: Int32 = STDOUT_FILENO) {
    _ = str.withCString { str in
        write(fd, str, strlen(str))
    }
}

func winsz_handler(sig: Int32) {
    render(char: nil)
}

var current: ((Int32?) -> BuiltinView)? = nil

public func render(char: Int32?) {
    var w: winsize = .init()
    _ = ioctl(STDOUT_FILENO, TIOCGWINSZ, &w)
    let size: Size = Size(width: Int(w.ws_col), height: Int(w.ws_row))
    clearScreen()
    move(to: Point(x: 1, y: 1))
    let implicit = current!(char)
    let s = implicit.size(for: ProposedSize(size))
    implicit.render(context: TTYRenderingContext(), size: s)
    
}

public func run<V: BuiltinView>(_ rootView: @escaping (Int32?) -> V) {
    current = { c in rootView(c).frame(maxWidth: .max, maxHeight: .max) }
    _ = enableRawMode(file: STDOUT_FILENO)
    render(char: nil)
    signal(SIGWINCH, winsz_handler)
    _ = enableRawMode(file: STDIN_FILENO)
    var c = getchar()
    while true {
        render(char: c)
        c = getchar()
    }
}