'use strict';

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


exports.DAT = function(core, pc, ins) {
	// do nothing and die
	return [];
}


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

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


exports.ADD = function(core, pc, ins) {
	if (ins.a.mode === AddrMode.Immediate) {
		const dst = core.getValue(pc, ins.b);
		dst.b.value += ins.a.value;
	} else {
		const src = core.getValue(pc, ins.a);
		const dst = core.getValue(pc, ins.b);
		dst.a.value += src.a.value;
		dst.b.value += src.b.value;
	}

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


exports.SUB = function(core, pc, ins) {
	if (ins.a.mode === AddrMode.Immediate) {
		const dst = core.getValue(pc, ins.b);
		dst.b.value -= ins.a.value;
	} else {
		const src = core.getValue(pc, ins.a);
		const dst = core.getValue(pc, ins.b);
		dst.a.value -= src.a.value;
		dst.b.value -= src.b.value;
	}

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


exports.CMP = function(core, pc, ins) {
	if (ins.a.mode === AddrMode.Immediate) {
		const test = core.getValue(pc, ins.b);
		if (test.b.value === ins.a.value) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	} else {
		const left = core.getValue(pc, ins.a);
		const right = core.getValue(pc, ins.b);
		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 = function(core, pc, ins) {
	if (ins.a.mode === AddrMode.Immediate) {
		const test = core.getValue(pc, ins.b);
		if (ins.a.value < test.b.value) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	} else {
		const left = core.getValue(pc, ins.a);
		const right = core.getValue(pc, ins.b);
		if (left.b.value < right.b.value) {
			return [core.normalize(pc, 2)];
		} else {
			return [core.normalize(pc, 1)];
		}
	}
}


exports.JMP = function(core, pc, ins) {
	const dstLoc = core.getLocation(pc, ins.a);
	return [dstLoc];
}


exports.JMZ = function(core, pc, ins) {
	let test
	if (ins.b.mode === AddrMode.Immediate) {
		test = (ins.b.value === 0);
	} else {
		const src = core.getValue(pc, ins.b);
		test = (src.b.value === 0);
	}

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


exports.JMN = function(core, pc, ins) {
	let test;

	if (ins.b.mode === AddrMode.Immediate) {
		test = (ins.b.value !== 0);
	} else {
		const src = core.getValue(pc, ins.b);
		test = (src.b.value !== 0);
	}

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


exports.DJN = function(core, pc, ins) {
	let test;

	if (ins.b.mode === AddrMode.Immediate) {
		ins.b.value -= 1;
		test = (ins.b.value !== 0);
	} else {
		const src = core.getValue(pc, ins.b);
		src.b.value -= 1;
		test = (src.b.value !== 0);
	}

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


exports.SPL = function(core, pc, ins) {
	return [
		core.normalize(pc, 1),
		core.getLocation(pc, ins.a),
	];
}