'use strict';

const { AddrMode } = require('./enum.js');


function getOp(core, pc, op) {
	switch(op.mode) {
		case AddrMode.Immediate:
			return { mode: AddrMode.Immediate, value: op.value };
		default:
			return { mode: 'precomp', value: core.getLocation(pc, op) };
	}
}


function Instruction(f) {
	return function(core, pc, ins) {
		const a = getOp(core, pc, ins.a);
		const b = getOp(core, pc, ins.b);
		return f(core, pc, a, b);
	}
}


exports.DAT = Instruction((core, pc, a, b) => {
	// do nothing and die
	return [];
});


exports.MOV = Instruction((core, pc, a, b) => {
	if (a.mode === AddrMode.Immediate) {
		const dst = core.data[b.value];
		dst.b.value = a.value;
	} else {
		const src = core.data[a.value];
		// hacky deep copy
		core.data[b.value] = JSON.parse(JSON.stringify(src));
	}

	return [core.normalize(pc, 1)];
});


exports.ADD = Instruction((core, pc, a, b) => {
	if (a.mode === AddrMode.Immediate) {
		const dst = core.data[b.value];
		dst.b.value += a.value;
	} else {
		const src = core.data[a.value];
		const dst = core.data[b.value];
		dst.a.value += src.a.value;
		dst.b.value += src.b.value;
	}

	return [core.normalize(pc, 1)];
});


exports.SUB = Instruction((core, pc, a, b) => {
	if (a.mode === AddrMode.Immediate) {
		const dst = core.data[b.value];
		dst.b.value -= a.value;
	} else {
		const src = core.data[a.value];
		const dst = core.data[b.value];
		dst.a.value -= src.a.value;
		dst.b.value -= src.b.value;
	}

	return [core.normalize(pc, 1)];
});


exports.CMP = Instruction((core, pc, a, b) => {
	if (a.mode === AddrMode.Immediate) {
		const test = core.data[b.value];
		if (test.b.value === a.value) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	} else {
		const left = core.data[a.value];
		const right = core.data[b.value];
		if (
			// compare opcode
			left.opcode  === right.opcode  &&
			// compare a-field
			left.a.mode  === right.a.mode  &&
			left.a.value === right.a.value &&
			// compare b-field
			left.b.mode  === right.b.mode  &&
			left.b.value === right.b.value
		) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	}
});


exports.SLT = Instruction((core, pc, a, b) => {
	if (a.mode === AddrMode.Immediate) {
		const test = core.data[b.value];
		if (a.value < test.b.value) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	} else {
		const left = core.data[a.value];
		const right = core.data[b.value];
		if (left.b.value < right.b.value) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	}
});


exports.JMP = Instruction((core, pc, a, b) => {
	return [a.value];
});


exports.JMZ = Instruction((core, pc, a, b) => {
	let test
	if (b.mode === AddrMode.Immediate) {
		test = (b.value === 0);
	} else {
		const src = core.data[b.value];
		test = (src.b.value === 0);
	}

	if (test) {
		return [a.value];
	} else {
		return [core.normalize(pc, 1)];
	}
});


exports.JMN = Instruction((core, pc, a, b) => {
	let test;

	if (b.mode === AddrMode.Immediate) {
		test = (b.value !== 0);
	} else {
		const src = core.data[b.value];
		test = (src.b.value !== 0);
	}

	if (test) {
		return [a.value];
	} else {
		return [core.normalize(pc, 1)];
	}
});


exports.DJN = Instruction((core, pc, a, b) => {
	let test;

	if (b.mode === AddrMode.Immediate) {
		core.data[pc].b.value -= 1;
		b.value -= 1;
		test = (b.value !== 0);
	} else {
		const src = core.data[b.value];
		src.b.value -= 1;
		test = (src.b.value !== 0);
	}

	if (test) {
		return [a.value];
	} else {
		return [core.normalize(pc, 1)];
	}
});


exports.SPL = Instruction((core, pc, a, b) => {
	return [
		core.normalize(pc, 1),
		a.value,
	];
});