107 lines
2.5 KiB
TypeScript
107 lines
2.5 KiB
TypeScript
import { escapeHtml } from "./helpers";
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import { AtLeast, Choose, End, Regex, Sequence, Use } from "./peg";
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export type Word = {
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text: string;
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};
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export type Command = Word[];
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export type Script = Command[];
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const InterCommandWhitespace = Regex(/\s+/y).expects("whitespace");
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const Comment = Regex(/#[^\n]*/y)
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.expects("#")
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.map(() => []);
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const PreCommand = AtLeast(0, InterCommandWhitespace);
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const PreWordWhitespace = Regex(/[^\S\n;]+/y).expects("whitespace");
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const BasicWord = Regex(/(?!\{)[^\s;]+/y)
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.map(([word]) => ({ text: word }))
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.expects("BASIC_WORD");
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// WIP, need to be able to escape braces correctly
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const Brace = Sequence(
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Regex(/\{/y).expects("{"),
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AtLeast(
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0,
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Choose(
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Use(() => Brace)
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.expects("{")
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.map((text) => `{${text}}`),
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Regex(/[^{}]+/y)
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.expects("text")
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.map(([text]) => text)
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)
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),
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Regex(/\}/y).expects("}")
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).map(([_left, fragments, _right]) => fragments.join(""));
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const Word = Choose(
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BasicWord,
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Brace.map((text) => ({ text }))
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);
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const CommandTerminator = Regex(/[\n;]/y)
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.expects("NEWLINE | ;")
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.map(() => true);
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const Command = Sequence(
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Word,
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AtLeast(
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0,
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Sequence(PreWordWhitespace, Word).map(([, word]) => word)
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),
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AtLeast(0, PreWordWhitespace)
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).map(([word, moreWords]) => [word].concat(moreWords));
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const Script = Sequence(
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AtLeast(
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0,
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Choose(
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PreWordWhitespace.map(() => []),
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CommandTerminator.map(() => []),
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Sequence(Comment, Choose(CommandTerminator, End())).map(() => []),
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Sequence(Command, Choose(CommandTerminator, End())).map(
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([words]) => words
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)
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)
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),
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End()
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).map(([commands]) => commands.filter((command) => command.length > 0));
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const ERROR_CONTEXT = /(?<=([^\n]{0,50}))([^\n]{0,50})/y;
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/**
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* Parse out a Notcl script into an easier-to-interpret representation.
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* No script is actually executed yet.
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*
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* @param - code to parse
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* @returns - parsed list of commands, or error message on failure
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*/
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export function parse(code: string): [true, Script] | [false, string] {
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/* Preprocess */
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// fold line endings
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code = code.replace(/(?<!\\)((\\\\)*)\\\n/g, "$1");
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/* Parse */
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const [commands, errorPos, expected] = Script(code, 0);
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if (commands) {
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return [true, commands[0]];
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} else {
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ERROR_CONTEXT.lastIndex = errorPos;
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const [, before, after] = ERROR_CONTEXT.exec(code)!;
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return [
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false,
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`<pre>Error at position ${errorPos}
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${escapeHtml(before + "" + after)}
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${"-".repeat(before.length)}^
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Expected: ${escapeHtml(expected)}</pre>`,
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];
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}
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}
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