import * as Binutils from "./binutils.mjs"

const FLAG_NEGATIVE = 1 << 0
const FLAG_HALT = 1 << 1
const FLAG_ABLAZE = 1 << 2

class Instruction {
    constructor(name, args, description) {
        this.Name = name
        this.Args = args
        this.Description = description
    }
}

const Instructions = [
    new Instruction("NOOP", [], "Do nothing"),
    new Instruction("PRNT", ["x"], "Print string at x"),
    new Instruction("READ", ["x"], "Read input, store in x"),
    new Instruction("CMPS", ["x", "y"], "Compare string x to string y"),
    new Instruction("JNEQ", ["x"], "If not equal, set PC to x"),
    new Instruction("JUMP", ["x"], "Set PC to x"),
    new Instruction("HALT", [], "Terminate program"),
    new Instruction("HACF", [], "Halt And Catch Fire (never use this!)"),
]

function disassemble(program) {
    let b = program[0]
    let inst = Instructions[b]
    if (inst) {
        let nargs = inst.Args.length
        let args = []
        for (let i = 0; i < nargs; i++) {
            args.push(program[i+1])
        }

        if (1+nargs <= program.length) {
            // Only return an opcode if there was enough data for its arguments as well
            return {length: 1+nargs, name: inst.Name, args: args}
        }
    }

    let data = Binutils.CString(program, true)
    let s = Binutils.Stringify(data)
    return {length: data.length, name: "DATA", args: [s]}
}

class CPU {
    /**
     * @param {Uint8Array} program Program to load
     * @param {string} input input string
     * @param {Number} pc initial program counter
     * @param {Number} flags initial flags
     */
    constructor(program, input, output="", pc=0, flags=0) {
        this.Program = program
        this.Input = input
        this.Output = output
        this.PC = pc
        this.Flags = flags
    }

    Clone() {
        return new CPU(this.Program, this.Input, this.Output, this.PC, this.Flags)
    }

    DisassembleProgram() {
        let ret = []
        let prog1 = this.Program.slice(0, this.PC)
        let addr = 0
        for (let prog of [prog1, this.Program]) {
            while (addr < prog.length) {
                let subprog = prog.slice(addr)
                let inst = disassemble(subprog)
                ret.push({
                    addr,
                    buf: this.Program.slice(addr, addr+inst.length), 
                    name: inst.name, 
                    args: inst.args,
                })
                addr += inst.length                    
            }
        }
        return ret
    }

    Step() {
        let prog = this.Program.slice(this.PC)
        let inst = disassemble(prog)
        this.Flags = 0
        switch (inst.name) {
            case "JUMP":
                this.PC = inst.args[0]
                return
            case "JNEQ":
                if (this.Flags && FLAG_NEGATIVE) {
                    this.PC = inst.args[0]
                    return
                }
                break
            case "READ": {
                let addr = inst.args[0]
                let b = new TextEncoder().encode(this.Input + "\0")
                let newproglen = Math.max(this.Program.length, addr+b.length)
                let newprog = new Uint8Array(newproglen)

                for (let i = 0; i < addr; i++) {
                    newprog[i] = this.Program[i]
                }
                for (let i = 0; i < b.length; i++) {
                    newprog[addr+i] = b[i]
                }
                for (let i = addr+b.length; i < this.Program.length; i++) {
                    newprog[i] = this.Program[i]
                }
                this.Program = newprog
                break
            }
            case "PRNT": {
                let addr = inst.args[0]
                let prog = this.Program.slice(addr)
                this.Output = Binutils.CString(prog)
                console.log(addr, this.Output)
                break
            }
            case "CMPS": {
                let a = Binutils.CString(this.Program.slice(inst.args[0]))
                let b = Binutils.CString(this.Program.slice(inst.args[1]))
                if (a == b) {
                    this.Flags = FLAG_NEGATIVE
                }
            }
            case "HALT":
                // Don't modify PC
                this.Flags = FLAG_HALT
                return
            case "HACF":
                this.Flags = FLAG_HALT | FLAG_ABLAZE
                return
            case "DATA":
                // Keep stepping through data one byte at a time trying to execute something
                inst.length = 1
                break
        }
        this.PC += inst.length
    }
}

class Triscit {
    constructor(program=[]) {
        this.program = program
        this.Init()
        this.Reset()
    }

    Init() {
        for (let e of document.querySelectorAll("[data-control]")) {
            switch (e.dataset.control) {
            case "step":
                e.addEventListener("click", () => this.Step())
                break
            case "back":
                e.addEventListener("click", () => this.Unstep())
                break
            case "reset":
                e.addEventListener("click", () => this.Reset())
                break
            case "input":
                e.addEventListener("input", () => this.SetInput())
                break
            case "program":
                e.addEventListener("input", () => this.SetProgram())
            }
        }

        let ih = document.querySelector("#instructions-help")
        for (let i = 0; i < Instructions.length; i++) {
            let inst = Instructions[i]
            let doc = document.querySelector("template#instruction-help").content.cloneNode(true)
            let tr = doc.firstElementChild
            tr.querySelector(".num").textContent = i
            tr.querySelector(".name").textContent = inst.Name
            tr.querySelector(".description").textContent = inst.Description
            ih.appendChild(doc)
        }

        this.SetInput()
        this.SetProgram()
    }

    Reset() {
        this.cpu = new CPU(this.program, this.input)
        this.stack = []
        this.Refresh()
    }

    Refresh() {
        let inste = document.querySelector("#instructions")
        while (inste.firstChild) inste.firstChild.remove()
        for (let i of this.cpu.DisassembleProgram()) {
            let doc = document.querySelector("template#instruction").content.cloneNode(true)
            let tr = doc.firstElementChild
            tr.querySelector(".addr").textContent = i.addr
            tr.querySelector(".name").textContent = i.name
            tr.querySelector(".hex").textContent = Binutils.Hexlify(i.buf)
            
            let args = tr.querySelector(".args")
            for (let a of i.args) {
                args.textContent += `${a} `
            }

            if (i.addr == this.cpu.PC) {
                tr.classList.add("is-selected")
            }
            inste.appendChild(tr)
        }

        for (let e of document.querySelectorAll("[data-flag]")) {
            let mask = 0
            let className = "is-info"
            switch (e.dataset.flag) {
            case "negative":
                mask = FLAG_NEGATIVE
                break
            case "halt":
                mask = FLAG_HALT
                break
            case "fire":
                mask = FLAG_ABLAZE
                className = "is-danger"
                break
            }
            if (this.cpu.Flags & mask) {
                e.classList.add(className)
            } else {
                e.classList.remove(className)
            }
        }

        for (let e of document.querySelectorAll("[data-value]")) {
            switch (e.dataset.value) {
            case "pc":
                e.textContent = this.cpu.PC
                break
            case "output":
                console.log(this.cpu.Output)
                e.value = Binutils.Stringify(this.cpu.Output)
                break
            }
        }
    }

    Step() {
        if (this.cpu.Flags & FLAG_HALT) {
            return
        }
        this.stack.push(this.cpu)
        this.cpu = this.cpu.Clone()
        this.cpu.Step()
        this.Refresh()
    }

    Unstep() {
        if (this.stack.length == 0) {
            return
        }
        this.cpu = this.stack.pop()
        this.Refresh()
    }

    SetProgram() {
        let e =document.querySelector('[data-control="program"]')
        this.program = Binutils.Unhexlify(e.value || "")
        this.Reset()
    }

    SetInput() {
        let e = document.querySelector('[data-control="input"]')
        let v = e.value || ""
        this.input = Binutils.Unescape(v)
        this.Reset()
    }
}

function init() {
    let app = new Triscit()
    window.app = app
}

if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", init)
} else {
    init()
}