import { Context } from "@logtail/types";
import { dirname, relative } from "path";
import stackTrace, { StackFrame } from "stack-trace";
import { Logtail } from "@logtail/node";

/**
 * Determines the file name and the line number from which the log
 * was initiated (if we're able to tell).
 *
 * @returns Context The caller's filename and the line number
 */
export function getStackContext(logtail: Logtail): Context {
  const stackFrame = getCallingFrame(logtail);
  if (stackFrame === null) return {};

  return {
    context: {
      runtime: {
        file: relativeToMainModule(stackFrame.getFileName()),
        type: stackFrame.getTypeName(),
        method: stackFrame.getMethodName(),
        function: stackFrame.getFunctionName(),
        line: stackFrame.getLineNumber(),
        column: stackFrame.getColumnNumber(),
      },
      system: {
        pid: process.pid,
        main_file: mainFileName(),
      },
    },
  };
}

function getCallingFrame(logtail: Logtail): StackFrame | null {
  for (let fn of [
    logtail.info,
    logtail.warn,
    logtail.error,
    logtail.log,
    logtail,
  ]) {
    const stack = stackTrace.get(fn as any);
    if (stack.length > 0) {
      return stack[0];
    }
  }

  return null;
}

function relativeToMainModule(fileName: string): string | null {
  if (typeof fileName !== "string") {
    return null;
  } else if (fileName.startsWith("file:/")) {
    const url = new URL(fileName);
    return url.pathname;
  } else {
    const rootPath = dirname(mainFileName());
    return relative(rootPath, fileName);
  }
}

function mainFileName(): string {
  return require?.main?.filename ?? "";
}