nostr-mailing-list/imapParsing.ts

export type ImapCommandParameters = string | string[] | Record<string, any>;

export function parseImapCommand(commandString: string): {
  tag: string;
  command: string;
  parameters: ImapCommandParameters[];
} {
  const parts: string[] = [];
  let currentPart = "";
  let inQuotes = false;
  let parenDepth = 0;
  let bracketDepth = 0;

  for (let i = 0; i < commandString.length; i++) {
    const char = commandString[i];

    if (char === '"' && (i === 0 || commandString[i - 1] !== "\\")) {
      inQuotes = !inQuotes;
      currentPart += char;
    } else if (char === "(" && !inQuotes) {
      parenDepth++;
      currentPart += char;
    } else if (char === ")" && !inQuotes) {
      parenDepth--;
      currentPart += char;
    } else if (char === "[" && !inQuotes) {
      bracketDepth++;
      currentPart += char;
    } else if (char === "]" && !inQuotes) {
      bracketDepth--;
      currentPart += char;
    } else if (
      char === " " && !inQuotes && parenDepth === 0 && bracketDepth === 0
    ) {
      if (currentPart) {
        parts.push(currentPart);
        currentPart = "";
      }
    } else {
      currentPart += char;
    }
  }

  if (currentPart) {
    parts.push(currentPart);
  }

  if (parts.length < 2) {
    throw new Error("Invalid command");
  }

  const tag = parts[0];

  let command = parts[1];
  let paramStartIdx = 2;

  if (command.toUpperCase() === "UID") {
    command = `${command} ${parts[2]}`;
    paramStartIdx = 3;
  }

  const parameters: ImapCommandParameters[] = [];

  for (let i = paramStartIdx; i < parts.length; i++) {
    let part = parts[i];

    if (part.startsWith('"') && part.endsWith('"')) {
      part = part.slice(1, -1);
    }

    if (part.includes('\\"')) {
      parameters.push(part.split('\\"'));
    } else if (part.startsWith("(") && part.endsWith(")")) {
      parameters.push(parseDataItems(part));
    } else {
      parameters.push(part);
    }
  }

  return {
    tag,
    command,
    parameters,
  };
}

export function parseDataItems(
  dataItemsString: string,
): ImapCommandParameters[] {
  const inner = dataItemsString.slice(1, -1).trim();

  if (!inner) return [];

  const result: ImapCommandParameters[] = [];
  let current = "";
  let inQuotes = false;
  let parenDepth = 0;
  let bracketDepth = 0;
  let fullSectionId = "";

  for (let i = 0; i < inner.length; i++) {
    const char = inner[i];

    if (char === '"' && (i === 0 || inner[i - 1] !== "\\")) {
      inQuotes = !inQuotes;
      current += char;
    } else if (char === "[" && !inQuotes) {
      bracketDepth++;

      if (
        current.toUpperCase().startsWith("BODY.PEEK") ||
        current.toUpperCase() === "BODY"
      ) {
        fullSectionId = current + char;
        current += char;
      } else {
        current += char;
      }
    } else if (char === "(" && !inQuotes) {
      parenDepth++;

      if (bracketDepth > 0 && fullSectionId) {
        fullSectionId = current;
        current = "";
      } else {
        current += char;
      }
    } else if (char === ")" && !inQuotes) {
      parenDepth--;

      if (parenDepth === 0 && bracketDepth > 0 && fullSectionId) {
        const fieldList = current.split(/\s+/).filter(Boolean);
        current = fieldList;
      } else {
        current += char;
      }
    } else if (char === "]" && !inQuotes) {
      bracketDepth--;

      if (bracketDepth === 0 && fullSectionId) {
        if (Array.isArray(current)) {
          const sectionObj: Record<string, string[]> = {};
          sectionObj[`${fullSectionId.trim()}]`] = current;
          result.push(sectionObj);
        } else {
          result.push(`${fullSectionId}${current}]`);
        }

        fullSectionId = "";
        current = "";
      } else if (fullSectionId) {
        current += char;
      } else {
        current += char;
      }
    } else if (
      char === " " && !inQuotes && parenDepth === 0 && bracketDepth === 0
    ) {
      if (current) {
        result.push(current);
        current = "";
      }
    } else {
      if (!Array.isArray(current)) {
        current += char;
      }
    }
  }

  if (current && !Array.isArray(current)) {
    result.push(current);
  }

  return result;
}