const MAX_SCRIPT_LINES = 200;
function parseMove(tokens, lineNumber) {
if (tokens.length !== 2) {
throw new Error(`line ${lineNumber}: MOVE must be written as \"MOVE <1-3>\"`);
}
const steps = Number.parseInt(tokens[1], 10);
if (Number.isNaN(steps) || steps < 1 || steps > 3) {
throw new Error(`line ${lineNumber}: MOVE steps must be an integer between 1 and 3`);
}
return { type: "MOVE", steps };
}
function parseRotate(tokens, lineNumber) {
if (tokens.length !== 2) {
throw new Error(`line ${lineNumber}: ROTATE must be written as \"ROTATE LEFT|RIGHT|NONE\"`);
}
const direction = tokens[1].toUpperCase();
if (!["LEFT", "RIGHT", "NONE", "0"].includes(direction)) {
throw new Error(`line ${lineNumber}: ROTATE direction must be LEFT, RIGHT, NONE, or 0`);
}
return {
type: "ROTATE",
direction: direction === "0" ? "NONE" : direction,
};
}
function parsePrimitive(tokens, lineNumber) {
const command = tokens[0].toUpperCase();
switch (command) {
case "MOVE":
return parseMove(tokens, lineNumber);
case "ROTATE":
return parseRotate(tokens, lineNumber);
case "SHOOT":
if (tokens.length !== 1) {
throw new Error(`line ${lineNumber}: SHOOT does not take arguments`);
}
return { type: "SHOOT" };
case "WAIT":
if (tokens.length !== 1) {
throw new Error(`line ${lineNumber}: WAIT does not take arguments`);
}
return { type: "WAIT" };
default:
throw new Error(`line ${lineNumber}: unsupported command \"${tokens[0]}\"`);
}
}
function parseConditional(tokens, lineNumber) {
if (tokens.length < 2) {
throw new Error(
`line ${lineNumber}: ${tokens[0]} must be written as \"${tokens[0]} <MOVE|ROTATE|SHOOT|WAIT ...>\"`
);
}
const condition = tokens[0].toUpperCase() === "IF_SEEN" ? "SEEN" : "NOT_SEEN";
const nestedTokens = tokens.slice(1);
const nestedCommand = nestedTokens[0].toUpperCase();
if (["IF_SEEN", "IF_NOT_SEEN"].includes(nestedCommand)) {
throw new Error(`line ${lineNumber}: nested IF statements are not supported`);
}
const thenAction = parsePrimitive(nestedTokens, lineNumber);
return {
type: "IF",
condition,
then: thenAction,
};
}
function parseSingleLine(rawLine, lineNumber) {
const trimmed = rawLine.trim();
if (!trimmed || trimmed.startsWith("#")) {
return null;
}
const tokens = trimmed.split(/\s+/);
const command = tokens[0].toUpperCase();
if (command === "IF_SEEN" || command === "IF_NOT_SEEN") {
return parseConditional(tokens, lineNumber);
}
return parsePrimitive(tokens, lineNumber);
}
function parseRobotScript(scriptText) {
if (typeof scriptText !== "string" || !scriptText.trim()) {
throw new Error("script is empty");
}
const lines = scriptText.split(/\r?\n/);
if (lines.length > MAX_SCRIPT_LINES) {
throw new Error(`script is too long; maximum ${MAX_SCRIPT_LINES} lines`);
}
const actions = [];
lines.forEach((line, index) => {
const parsed = parseSingleLine(line, index + 1);
if (parsed) {
actions.push(parsed);
}
});
if (!actions.length) {
throw new Error("script has no executable commands");
}
return actions;
}
module.exports = {
parseRobotScript,
};
