Add dotenv file operations

src/dotenv/document.ts

@@ -0,0 +1,195 @@
+export type DotenvIssue = {
+  line: number;
+  column: number;
+  message: string;
+};
+
+export type DotenvParsedAssignment = {
+  line: number;
+  raw: string;
+  leadingWhitespace: string;
+  exported: boolean;
+  key: string;
+  keyColumn: number;
+  beforeEqWhitespace: string;
+  afterEqRaw: string;
+  quote: 'none' | 'single' | 'double';
+  value: string;
+};
+
+export type DotenvLine =
+  | { kind: 'blank'; line: number; raw: string }
+  | { kind: 'comment'; line: number; raw: string }
+  | ({ kind: 'assignment' } & DotenvParsedAssignment)
+  | { kind: 'unknown'; line: number; raw: string };
+
+export type DotenvDocument = {
+  lines: DotenvLine[];
+  issues: DotenvIssue[];
+  endsWithNewline: boolean;
+};
+
+function isWhitespace(char: string): boolean {
+  return /\s/.test(char);
+}
+
+function isValidKeyChar(char: string): boolean {
+  return /[A-Za-z0-9_]/.test(char);
+}
+
+function stripInlineComment(unquotedValue: string): string {
+  for (let i = 0; i < unquotedValue.length; i++) {
+    const c = unquotedValue[i];
+    if (c === '#') {
+      const prev = i > 0 ? (unquotedValue[i - 1] ?? '') : '';
+      if (prev === '' || /\s/.test(prev)) return unquotedValue.slice(0, i);
+    }
+  }
+  return unquotedValue;
+}
+
+function unescapeDoubleQuoted(value: string): string {
+  let out = '';
+  for (let i = 0; i < value.length; i++) {
+    const c = value[i];
+    if (c !== '\\') {
+      out += c;
+      continue;
+    }
+    const next = value[i + 1];
+    if (next === undefined) {
+      out += '\\';
+      continue;
+    }
+    i++;
+    if (next === 'n') out += '\n';
+    else if (next === 'r') out += '\r';
+    else if (next === 't') out += '\t';
+    else out += next;
+  }
+  return out;
+}
+
+function parseValueDetailed(afterEqRaw: string, line: number, issues: DotenvIssue[]): { value: string; quote: 'none' | 'single' | 'double' } {
+  const trimmed = afterEqRaw.trimStart();
+  if (!trimmed) return { value: '', quote: 'none' };
+
+  const first = trimmed[0];
+  if (first === "'") {
+    const end = trimmed.indexOf("'", 1);
+    if (end === -1) {
+      issues.push({ line, column: 1, message: 'Unterminated single-quoted value' });
+      return { value: trimmed.slice(1), quote: 'single' };
+    }
+    return { value: trimmed.slice(1, end), quote: 'single' };
+  }
+
+  if (first === '"') {
+    let end = 1;
+    for (; end < trimmed.length; end++) {
+      const c = trimmed[end];
+      if (c === '"' && trimmed[end - 1] !== '\\') break;
+    }
+    if (end >= trimmed.length || trimmed[end] !== '"') {
+      issues.push({ line, column: 1, message: 'Unterminated double-quoted value' });
+      return { value: unescapeDoubleQuoted(trimmed.slice(1)), quote: 'double' };
+    }
+    return { value: unescapeDoubleQuoted(trimmed.slice(1, end)), quote: 'double' };
+  }
+
+  return { value: stripInlineComment(trimmed).trimEnd(), quote: 'none' };
+}
+
+function parseAssignmentLine(raw: string, line: number, issues: DotenvIssue[]): DotenvParsedAssignment | undefined {
+  let cursor = 0;
+  while (cursor < raw.length && isWhitespace(raw[cursor] ?? '')) cursor++;
+  const leadingWhitespace = raw.slice(0, cursor);
+
+  let exported = false;
+  const exportStart = cursor;
+  if (raw.slice(cursor).startsWith('export')) {
+    const afterExport = raw[cursor + 'export'.length] ?? '';
+    if (isWhitespace(afterExport)) {
+      exported = true;
+      cursor += 'export'.length;
+      while (cursor < raw.length && isWhitespace(raw[cursor] ?? '')) cursor++;
+    } else {
+      cursor = exportStart;
+    }
+  }
+
+  const keyStart = cursor;
+  while (cursor < raw.length && isValidKeyChar(raw[cursor] ?? '')) cursor++;
+  const key = raw.slice(keyStart, cursor);
+  if (!key) {
+    issues.push({ line, column: keyStart + 1, message: 'Invalid key name' });
+    return undefined;
+  }
+
+  const next = raw[cursor] ?? '';
+  if (next && !isWhitespace(next) && next !== '=') {
+    issues.push({ line, column: cursor + 1, message: 'Invalid key name' });
+    return undefined;
+  }
+
+  const wsStart = cursor;
+  while (cursor < raw.length && isWhitespace(raw[cursor] ?? '')) cursor++;
+  const beforeEqWhitespace = raw.slice(wsStart, cursor);
+
+  if ((raw[cursor] ?? '') !== '=') {
+    issues.push({ line, column: cursor + 1, message: 'Missing = in assignment' });
+    return undefined;
+  }
+
+  const afterEqRaw = raw.slice(cursor + 1);
+  const { value, quote } = parseValueDetailed(afterEqRaw, line, issues);
+
+  return {
+    line,
+    raw,
+    leadingWhitespace,
+    exported,
+    key,
+    keyColumn: keyStart + 1,
+    beforeEqWhitespace,
+    afterEqRaw,
+    value,
+    quote
+  };
+}
+
+export function parseDotenvDocument(contents: string): DotenvDocument {
+  const issues: DotenvIssue[] = [];
+  const endsWithNewline = contents.endsWith('\n');
+
+  const split = contents.split(/\r?\n/);
+  if (endsWithNewline) split.pop();
+
+  const lines: DotenvLine[] = [];
+  for (let i = 0; i < split.length; i++) {
+    const lineNumber = i + 1;
+    const raw = split[i] ?? '';
+
+    const trimmed = raw.trim();
+    if (!trimmed) {
+      lines.push({ kind: 'blank', line: lineNumber, raw });
+      continue;
+    }
+
+    if (raw.trimStart().startsWith('#')) {
+      lines.push({ kind: 'comment', line: lineNumber, raw });
+      continue;
+    }
+
+    const parsed = parseAssignmentLine(raw, lineNumber, issues);
+    if (parsed) lines.push({ kind: 'assignment', ...parsed });
+    else lines.push({ kind: 'unknown', line: lineNumber, raw });
+  }
+
+  return { lines, issues, endsWithNewline };
+}
+
+export function stringifyDotenvDocument(doc: DotenvDocument): string {
+  const out = doc.lines.map((l) => l.raw).join('\n');
+  return doc.endsWithNewline ? `${out}\n` : out;
+}