import type { AssignStmt, Expr, Stmt } from "../ast"
import { R8 } from "../sm83/cpu"
import { Loc, LocType } from "./loc"
import type { Operand, AbsInsn2, AbsInsn3 } from "./insn"

export type IRState = {
    nextID: number
    insns: Array<AbsInsn2>
}

export const convertIR = (stmts: Array<Stmt>): Array<AbsInsn2> => {
    const state: IRState = {
        nextID: 0,
        insns: [],
    }

    stmts.forEach(stmt => {
        convertAssignStmt(state, stmt)
    })

    return state.insns
}

export const convertAssignStmt = (state: IRState, stmt: AssignStmt): void => {
    convertExpr(state, Loc.vari(stmt.args.name), stmt.args.expr)
}

export const convertExpr = (state: IRState, dest: Loc, expr: Expr): void => {
    const threeAddress = convertExpr3(state, dest, expr)

    threeAddress.forEach(ssa => {
        switch (ssa.type) {
            case 'copy':
                state.insns.push(ssa)
                break

            case 'unary':
                state.insns.push(
                    { type: "copy", dest: Loc.reg(R8.A), source: ssa.source },
                    { type: "unary", dest: Loc.reg(R8.A), source: Loc.reg(R8.A), op: ssa.op },
                    { type: "copy", dest: ssa.dest, source: Loc.reg(R8.A) },
                )
                break

            case 'binary':
                let source1 = ssa.source1
                if (typeof source1 !== 'number' && source1.type === LocType.VARIABLE) {
                    source1 = Loc.temp(`t${state.nextID++}`)
                    state.insns.push(
                        { type: "copy", dest: Loc.reg(R8.A), source: ssa.source1 },
                        { type: "copy", dest: source1, source: Loc.reg(R8.A) },
                    )
                }

                state.insns.push(
                    { type: "copy", dest: Loc.reg(R8.A), source: ssa.source },
                    { type: "unary", dest: Loc.reg(R8.A), op: ssa.op, source: source1 },
                    { type: "copy", dest: ssa.dest, source: Loc.reg(R8.A) },
                )
                break
        }
    })
}

export const convertExpr3 = (state: IRState, dest: Loc, expr: Expr): Array<AbsInsn3> => {
    let expr_stmts: Array<AbsInsn3> = []

    if (typeof expr === "number") {
        expr_stmts = [{ type: "copy", dest, source: expr }]
    } else if (typeof expr === "string") {
        expr_stmts = [{ type: "copy", dest, source: Loc.vari(expr) }]
    } else if (expr.type === "unary") {
        const [source, stmts] = getSource(state, expr.arg)
        stmts.push({
            type: "unary",
            dest,
            op: expr.op,
            source,
        })

        expr_stmts = stmts
    } else {
        const [left_source, left_stmts] = getSource(state, expr.left)
        const [right_source, right_stmts] = getSource(state, expr.right)

        const stmts = [...left_stmts, ...right_stmts]
        stmts.push({
            type: "binary",
            dest,
            op: expr.op,
            source: left_source,
            source1: right_source,
        })

        expr_stmts = stmts
    }

    return expr_stmts
}

const getSource = (state: IRState, expr: Expr): [Operand, Array<AbsInsn3>] => {
    if (typeof expr === "number") {
        return [expr, []]
    } else if (typeof expr === "string") {
        return [Loc.vari(expr), []]
    }

    const source = Loc.temp(`t${state.nextID++}`)
    const stmts = convertExpr3(state, source, expr)
    return [source, stmts]
}