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@@ -0,0 +1,101 @@
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+import * as AST from "./ast";
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+import Error, { isError } from "./error";
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+import Token, { TokenKind } from "./token";
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+
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+export default class Parser {
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+ public tokens: Token[];
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+ public position: number;
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+
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+ constructor(tokens: Token[]) {
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+ this.tokens = tokens;
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+ this.position = 0;
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+ }
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+
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+ public parse(): AST.Statement[] | Error {
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+ const tree: AST.Statement[] = [];
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+
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+ while (!this.atEnd()) {
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+ const stmt = this.statement();
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+ if (isError(stmt)) {
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+ return stmt;
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+ } else {
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+ tree.push(stmt);
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+ }
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+ }
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+
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+ return tree;
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+ }
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+
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+ private statement(): AST.Statement | Error {
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+ const token = this.currentToken();
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+
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+ switch (token.kind) {
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+ case TokenKind.SELECT:
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+ return this.select();
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+ }
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+
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+ return new Error(`Unexpected token ${token.kind}`, token.line);
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+ }
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+
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+ private select(): AST.Statement | Error {
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+ this.eat(TokenKind.SELECT);
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+ const args = this.args();
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+ if (isError(args)) {
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+ return args;
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+ }
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+ return new AST.Statement({
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+ arguments: args,
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+ type: AST.StatementType.SELECT,
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+ });
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+ }
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+
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+ private args(): AST.Number[] | Error {
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+ const args = [];
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+
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+ while (true) {
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+ const arg = this.number();
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+ if (isError(arg)) {
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+ return arg;
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+ }
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+ args.push(arg);
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+
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+ if (this.currentToken().kind === TokenKind.COMMA) {
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+ this.eat(TokenKind.COMMA);
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+ } else {
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+ break;
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+ }
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+ }
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+
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+ return args;
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+ }
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+
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+ private number(): AST.Number | Error {
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+ const n = this.eat(TokenKind.NUMBER);
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+ if (isError(n)) {
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+ return n;
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+ }
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+ return new AST.Number(parseFloat(n.value || ""));
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+ }
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+
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+ private eat(kind: TokenKind) {
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+ const token = this.currentToken();
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+ if (token.kind === kind) {
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+ this.advance();
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+ return token;
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+ }
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+
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+ return new Error(`Unexpected token ${token}`, token.line);
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+ }
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+
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+ private currentToken(): Token {
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+ return this.tokens[this.position];
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+ }
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+
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+ private advance() {
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+ this.position += 1;
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+ }
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+
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+ private atEnd(): boolean {
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+ return this.currentToken().kind === TokenKind.EOF;
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+ }
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+}
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