import { isCI } from 'ci-info';
import { noop } from 'foxts/noop';
import { basename, extname } from 'node:path';
import process from 'node:process';
import picocolors from 'picocolors';

export const SPAN_STATUS_START = 0;
export const SPAN_STATUS_END = 1;

const spanTag = Symbol('span');

export interface TraceResult {
  name: string,
  start: number,
  end: number,
  children: TraceResult[]
}

/** Pure data object — safe to transfer across Worker Thread boundaries. */
export interface RawSpan {
  traceResult: TraceResult,
  status: typeof SPAN_STATUS_START | typeof SPAN_STATUS_END
}

export interface Span {
  [spanTag]: true,
  readonly rawSpan: RawSpan,
  readonly stop: (time?: number) => void,
  readonly traceChild: (name: string) => Span,
  readonly traceSyncFn: <T>(fn: (span: Span) => T) => T,
  readonly traceAsyncFn: <T>(fn: (span: Span) => T | Promise<T>) => Promise<T>,
  readonly tracePromise: <T>(promise: Promise<T>) => Promise<T>,
  readonly traceChildSync: <T>(name: string, fn: (span: Span) => T) => T,
  readonly traceChildAsync: <T>(name: string, fn: (span: Span) => Promise<T>) => Promise<T>,
  readonly traceChildPromise: <T>(name: string, promise: Promise<T>) => Promise<T>,
  readonly traceWorkerChild: <T>(name: string, factory: (rawSpan: RawSpan) => Promise<WorkerJobResult<T>>) => Promise<T>,
  readonly traceResult: TraceResult
}

/**
 * Wraps a serializable {@link RawSpan} with all span methods.
 * Use this on a worker thread after receiving a {@link RawSpan} (or {@link TraceResult})
 * transferred from another thread.
 */
export function makeSpan(rawSpan: RawSpan): Span {
  const { traceResult } = rawSpan;

  const stop = (time?: number) => {
    if (rawSpan.status === SPAN_STATUS_END) {
      throw new Error(`span already stopped: ${traceResult.name}`);
    }
    traceResult.end = time ?? performance.now();
    rawSpan.status = SPAN_STATUS_END;
  };

  const traceChild = (name: string) => createSpan(name, traceResult);

  const span: Span = {
    [spanTag]: true,
    rawSpan,
    stop,
    traceChild,
    traceSyncFn<T>(fn: (span: Span) => T) {
      const res = fn(span);
      span.stop();
      return res;
    },
    async traceAsyncFn<T>(fn: (span: Span) => T | Promise<T>): Promise<T> {
      const res = await fn(span);
      span.stop();
      return res;
    },
    traceResult,
    async tracePromise<T>(promise: Promise<T>): Promise<T> {
      const res = await promise;
      span.stop();
      return res;
    },
    traceChildSync: <T>(name: string, fn: (span: Span) => T): T => traceChild(name).traceSyncFn(fn),
    traceChildAsync: <T>(name: string, fn: (span: Span) => T | Promise<T>): Promise<T> => traceChild(name).traceAsyncFn(fn),
    traceChildPromise: <T>(name: string, promise: Promise<T>): Promise<T> => traceChild(name).tracePromise(promise),

    async traceWorkerChild<T>(name: string, factory: (rawSpan: RawSpan) => Promise<WorkerJobResult<T>>): Promise<T> {
      const childSpan = traceChild(name);
      const { result, traceResult, workerTimeOrigin } = await factory(childSpan.rawSpan);
      mergeWorkerTrace(childSpan, traceResult, workerTimeOrigin);
      childSpan.stop();
      return result;
    }
  };

  // eslint-disable-next-line sukka/no-redundant-variable -- self reference
  return span;
}

export function createSpan(name: string, parentTraceResult?: TraceResult): Span {
  const rawSpan: RawSpan = {
    traceResult: {
      name,
      start: performance.now(),
      end: 0,
      children: []
    },
    status: SPAN_STATUS_START
  };

  parentTraceResult?.children.push(rawSpan.traceResult);

  return makeSpan(rawSpan);
}

export const dummySpan = createSpan('dummy');

export function task(importMetaMain: boolean, importMetaPath: string) {
  return (fn: (span: Span, onCleanup: (cb: () => Promise<void> | void) => void) => Promise<unknown>, customName?: string) => {
    const taskName = customName ?? basename(importMetaPath, extname(importMetaPath));
    let cleanup: () => Promise<void> | void = noop;
    const onCleanup = (cb: () => void) => {
      cleanup = cb;
    };

    if (importMetaMain) {
      const innerSpan = createSpan(taskName);

      process.on('uncaughtException', (error) => {
        console.error('Uncaught exception:', error);
        process.exit(1);
      });
      process.on('unhandledRejection', (reason) => {
        console.error('Unhandled rejection:', reason);
        process.exit(1);
      });

      innerSpan.traceChildAsync('dummy', (childSpan) => fn(childSpan, onCleanup)).finally(() => {
        innerSpan.stop();
        printTraceResult(innerSpan.traceResult);
        process.nextTick(whyIsNodeRunning);
        process.nextTick(() => process.exit(0));
      });
    }

    let runSpan: Span;
    async function run(parentSpan?: Span | null): Promise<TraceResult> {
      if (parentSpan) {
        runSpan = parentSpan.traceChild(taskName);
      } else {
        runSpan = createSpan(taskName);
      }

      try {
        await fn(runSpan, onCleanup);
      } finally {
        runSpan.stop();
        cleanup();
      }

      return runSpan.traceResult;
    }

    return Object.assign(run, {
      getInternalTraceResult: () => runSpan.traceResult
    });
  };
}

export async function whyIsNodeRunning() {
  if (isCI && process.env.RUNNER_DEBUG === '1') {
    const mod = await import('why-is-node-running');
    return mod.default();
  }
}

// const isSpan = (obj: any): obj is Span => {
//   return typeof obj === 'object' && obj && spanTag in obj;
// };
// export const universalify = <A extends any[], R>(taskname: string, fn: (this: void, ...args: A) => R) => {
//   return (...args: A) => {
//     const lastArg = args[args.length - 1];
//     if (isSpan(lastArg)) {
//       return lastArg.traceChild(taskname).traceSyncFn(() => fn(...args));
//     }
//     return fn(...args);
//   };
// };

function adjustTraceTimestamps(trace: TraceResult, offset: number): TraceResult {
  return {
    name: trace.name,
    start: trace.start + offset,
    end: trace.end + offset,
    children: trace.children.map(child => adjustTraceTimestamps(child, offset))
  };
}

function mergeWorkerTrace(
  parentSpan: Span,
  workerTraceResult: TraceResult,
  workerTimeOrigin: number
): void {
  const offset = workerTimeOrigin - performance.timeOrigin;
  for (const child of workerTraceResult.children) {
    parentSpan.traceResult.children.push(adjustTraceTimestamps(child, offset));
  }
}

/** The envelope that a worker function returns so the main thread can recover both the result and the trace. */
export interface WorkerJobResult<T> {
  result: T,
  traceResult: TraceResult,
  workerTimeOrigin: number
}

/**
 * Worker-side wrapper.  Call this instead of manually constructing spans.
 *
 * - When `rawSpan` is provided (normal worker invocation from the main thread),
 *   it is wrapped with {@link makeSpan} so all child spans are attached to the
 *   caller's trace tree and can be recovered after the job finishes.
 * - When `rawSpan` is `undefined` (standalone / CLI invocation), a fresh
 *   child span of {@link dummySpan} is used instead.
 *
 * The impl function receives a full {@link Span} and returns its result
 * normally; the wrapper packages everything into a {@link WorkerJobResult}.
 */
export async function workerJob<T>(
  rawSpan: RawSpan | undefined,
  impl: (span: Span) => Promise<T>
): Promise<WorkerJobResult<T>> {
  const span = rawSpan == null ? dummySpan.traceChild('worker-standalone') : makeSpan(rawSpan);
  const result = await impl(span);
  return {
    result,
    traceResult: span.traceResult,
    workerTimeOrigin: performance.timeOrigin
  };
}

export function printTraceResult(traceResult: TraceResult) {
  printTree(
    traceResult,
    node => {
      if (node.end - node.start < 0) {
        return node.name;
      }
      return `${node.name} ${picocolors.bold(`${(node.end - node.start).toFixed(3)}ms`)}`;
    }
  );
}

function printTree(initialTree: TraceResult, printNode: (node: TraceResult, branch: string) => string) {
  function printBranch(tree: TraceResult, branch: string, isGraphHead: boolean, isChildOfLastBranch: boolean) {
    const children = tree.children;

    let branchHead = '';

    if (!isGraphHead) {
      branchHead = children.length > 0 ? '┬ ' : '─ ';
    }

    const toPrint = printNode(tree, `${branch}${branchHead}`);

    if (typeof toPrint === 'string') {
      console.log(`${branch}${branchHead}${toPrint}`);
    }

    let baseBranch = branch;

    if (!isGraphHead) {
      baseBranch = branch.slice(0, -2) + (isChildOfLastBranch ? '  ' : '│ ');
    }

    const nextBranch = `${baseBranch}├─`;
    const lastBranch = `${baseBranch}└─`;

    children.forEach((child, index) => {
      const last = children.length - 1 === index;
      printBranch(child, last ? lastBranch : nextBranch, false, last);
    });
  }

  printBranch(initialTree, '', true, false);
}

export function printStats(stats: TraceResult[]): void {
  const longestTaskName = Math.max(...stats.map(i => i.name.length));
  const realStart = Math.min(...stats.map(i => i.start));
  const realEnd = Math.max(...stats.map(i => i.end));

  const statsStep = ((realEnd - realStart) / 120) | 0;

  stats
    .sort((a, b) => a.start - b.start)
    .forEach(stat => {
      console.log(
        `[${stat.name}]${' '.repeat(longestTaskName - stat.name.length)}`,
        ' '.repeat(((stat.start - realStart) / statsStep) | 0),
        '='.repeat(Math.max(((stat.end - stat.start) / statsStep) | 0, 1))
      );
    });
}