/**
 * Frame represents a stack frame.
 */
export interface Frame {
  function: string | null;
  file: string;
  line: number;
  column: number;
}

/**
 * getStackTrace returns the current stack trace
 * with frames from the internals of the javascript runtime removed.
 */
export function getStackTrace(drop = 0): Frame[] {
  // First try to get the stack trace from an error
  const obj = new Error("placeholder");
  if (obj.stack) {
    let frames = extractFrames(obj.stack);
    if (frames && frames.length > drop) {
      frames = frames.slice(drop + 1);
      return frames.filter((frame) => !isCommonFrame(frame));
    }
  }

  return [];
}

/**
 * extractFrames extracts the frames from a stack trace string generated by Error.stack
 */
export function extractFrames(stack?: string): Frame[] | undefined {
  if (!stack) {
    return undefined;
  }

  const frames: Frame[] = [];
  const lines = stack.split("\n");
  for (const line of lines) {
    const frame = extractFrame(line);
    if (frame) {
      frames.push(frame);
    }
  }

  if (frames.length === 0) {
    return undefined;
  }

  return frames;
}

/**
 * isCommonFrame returns true if the frame is a common frame that should be ignored.
 * as it is outside the users code base (such as it comes from the node runtime).
 */
export function isCommonFrame(stack: Frame): boolean {
  // "node:" is a node internal frame
  // "bun:" is a bun internal frame
  // "" is a frame with no file, so a core JS function
  return (
    stack.file.startsWith("node:") ||
    stack.file.startsWith("bun:") ||
    stack.file === ""
  );
}

/**
 * Typeguard for a stack trace
 */
export function isStackFrames(stack: unknown): stack is Frame[] {
  if (stack === undefined || stack === null || !Array.isArray(stack)) {
    // This is not a stack trace
    return false;
  }
  if (stack.length === 0) {
    // This is a valid stack trace, just nothing is in it!
    return true;
  }

  // Check that every array element is a Frame
  for (const frame of stack) {
    if (typeof frame !== "object" || frame === null || frame === undefined) {
      return false;
    }
    if (
      typeof frame.function !== "string" ||
      typeof frame.file !== "string" ||
      typeof frame.line !== "number" ||
      typeof frame.column !== "number"
    ) {
      return false;
    }
  }
  return true;
}

const frameRegex = /^\s*at\s+(.+)\s+\((.*):(\d+):(\d+)\)\s*$/;
const frameRegex2 = /^\s*at\s+(.+):(\d+):(\d+)\s*$/;

function extractFrame(line: string): Frame | undefined {
  const parts = frameRegex.exec(line);
  if (parts) {
    return {
      function: parts[1],
      file: parts[2],
      line: parseInt(parts[3], 10),
      column: parseInt(parts[4], 10),
    };
  }

  const parts2 = frameRegex2.exec(line);
  if (parts2) {
    return {
      function: null,
      file: parts2[1],
      line: parseInt(parts2[2], 10),
      column: parseInt(parts2[3], 10),
    };
  }
  return undefined;
}