package expecter

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"regexp"
	"slices"
	"strings"
	"testing"
	"time"
	"unicode/utf8"

	"github.com/acarl005/stripansi"
	"github.com/stretchr/testify/require"
	"go.uber.org/atomic"
	"golang.org/x/xerrors"

	"github.com/coder/coder/v2/testutil"
	"github.com/coder/serpent"
)

func New(t *testing.T, r io.Reader, name string) *Expecter {
	// Use pipe for logging.
	logDone := make(chan struct{})
	logr, logw := io.Pipe()

	// Write to log and output buffer.
	copyDone := make(chan struct{})
	out := newStdbuf()
	w := io.MultiWriter(logw, out)

	ex := &Expecter{
		t:    t,
		out:  out,
		name: atomic.NewString(name),

		runeReader: bufio.NewReaderSize(out, utf8.UTFMax),
		logDone:    logDone,
		copyDone:   copyDone,
		logr:       logr,
		logw:       logw,
	}

	go func() {
		defer close(copyDone)
		_, err := io.Copy(w, r)
		ex.Logf("copy done: %v", err)
		ex.Logf("closing out")
		err = out.closeErr(err)
		ex.Logf("closed out: %v", err)
	}()

	// Log all output as part of test for easier debugging on errors.
	go func() {
		defer close(logDone)
		s := bufio.NewScanner(logr)
		for s.Scan() {
			ex.Logf("%q", stripansi.Strip(s.Text()))
		}
		// Surface non-EOF scanner errors; otherwise they're invisible.
		if err := s.Err(); err != nil {
			ex.Logf("log scanner stopped: %v", err)
		}
	}()

	return ex
}

func NewAttachedToInvocation(t *testing.T, invocation *serpent.Invocation) *Expecter {
	r, w := io.Pipe()
	invocation.Stdout = w
	invocation.Stderr = w
	e := New(t, r, "cmd")

	t.Cleanup(func() {
		// Serpent doesn't handle closing stdout after running the Invocation; normally the OS does that automatically when
		// the process exits. Close it here at the end of the test to ensure we don't leak goroutines reading from the
		// stdout/stderr.
		_ = w.Close()
		e.Close("test end")
	})
	return e
}

type Expecter struct {
	t    *testing.T
	out  *stdbuf
	name *atomic.String

	runeReader        *bufio.Reader
	copyDone, logDone chan struct{}
	logr, logw        io.Closer
}

// Rename the expecter. Make sure you set this before anything starts writing to the
// stream, or it may not be named consistently.
func (e *Expecter) Rename(name string) {
	e.name.Store(name)
}

func (e *Expecter) Close(reason string) {
	ctx, cancel := context.WithTimeout(context.Background(), testutil.WaitShort)
	defer cancel()

	e.Logf("closing expecter: %s", reason)

	// Caller needs to have closed the stream so that copying can complete
	select {
	case <-ctx.Done():
		e.fatalf("close", "copy did not close in time")
		return
	case <-e.copyDone:
	}

	e.logClose("logw", e.logw)
	e.logClose("logr", e.logr)
	select {
	case <-ctx.Done():
		e.fatalf("close", "log pipe did not close in time")
		return
	case <-e.logDone:
	}

	e.Logf("closed expecter")
}

func (e *Expecter) logClose(name string, c io.Closer) {
	e.Logf("closing %s", name)
	err := c.Close()
	e.Logf("closed %s: %v", name, err)
}

// Deprecated: use ExpectMatchContext instead.
// This uses a background context, so will not respect the test's context.
func (e *Expecter) ExpectMatch(str string) string {
	return e.expectMatchContextFunc(str, e.ExpectMatchContext)
}

func (e *Expecter) ExpectRegexMatch(str string) string {
	return e.expectMatchContextFunc(str, e.ExpectRegexMatchContext)
}

func (e *Expecter) expectMatchContextFunc(str string, fn func(ctx context.Context, str string) string) string {
	e.t.Helper()

	timeout, cancel := context.WithTimeout(context.Background(), testutil.WaitMedium)
	defer cancel()

	return fn(timeout, str)
}

// TODO(mafredri): Rename this to ExpectMatch when refactoring.
func (e *Expecter) ExpectMatchContext(ctx context.Context, str string) string {
	return e.expectMatcherFunc(ctx, str, strings.Contains)
}

func (e *Expecter) ExpectRegexMatchContext(ctx context.Context, str string) string {
	return e.expectMatcherFunc(ctx, str, func(src, pattern string) bool {
		return regexp.MustCompile(pattern).MatchString(src)
	})
}

func (e *Expecter) expectMatcherFunc(ctx context.Context, str string, fn func(src, pattern string) bool) string {
	e.t.Helper()

	var buffer bytes.Buffer
	err := e.doMatchWithDeadline(ctx, "ExpectMatchContext", func(rd *bufio.Reader) error {
		for {
			r, _, err := rd.ReadRune()
			if err != nil {
				return err
			}
			_, err = buffer.WriteRune(r)
			if err != nil {
				return err
			}
			if fn(buffer.String(), str) {
				return nil
			}
		}
	})
	if err != nil {
		e.fatalf("read error", "%v (wanted %q; got %q)", err, str, buffer.String())
		return ""
	}
	e.Logf("matched %q = %q", str, buffer.String())
	return buffer.String()
}

// ExpectNoMatchBefore validates that `match` does not occur before `before`.
func (e *Expecter) ExpectNoMatchBefore(ctx context.Context, match, before string) string {
	e.t.Helper()

	var buffer bytes.Buffer
	err := e.doMatchWithDeadline(ctx, "ExpectNoMatchBefore", func(rd *bufio.Reader) error {
		for {
			r, _, err := rd.ReadRune()
			if err != nil {
				return err
			}
			_, err = buffer.WriteRune(r)
			if err != nil {
				return err
			}

			if strings.Contains(buffer.String(), match) {
				return xerrors.Errorf("found %q before %q", match, before)
			}

			if strings.Contains(buffer.String(), before) {
				return nil
			}
		}
	})
	if err != nil {
		e.fatalf("read error", "%v (wanted no %q before %q; got %q)", err, match, before, buffer.String())
		return ""
	}
	e.Logf("matched %q = %q", before, stripansi.Strip(buffer.String()))
	return buffer.String()
}

func (e *Expecter) Peek(ctx context.Context, n int) []byte {
	e.t.Helper()

	var out []byte
	err := e.doMatchWithDeadline(ctx, "Peek", func(rd *bufio.Reader) error {
		var err error
		out, err = rd.Peek(n)
		return err
	})
	if err != nil {
		e.fatalf("read error", "%v (wanted %d bytes; got %d: %q)", err, n, len(out), out)
		return nil
	}
	e.Logf("peeked %d/%d bytes = %q", len(out), n, out)
	return slices.Clone(out)
}

//nolint:govet // We don't care about conforming to ReadRune() (rune, int, error).
func (e *Expecter) ReadRune(ctx context.Context) rune {
	e.t.Helper()

	var r rune
	err := e.doMatchWithDeadline(ctx, "ReadRune", func(rd *bufio.Reader) error {
		var err error
		r, _, err = rd.ReadRune()
		return err
	})
	if err != nil {
		e.fatalf("read error", "%v (wanted rune; got %q)", err, r)
		return 0
	}
	e.Logf("matched rune = %q", r)
	return r
}

func (e *Expecter) ReadLine(ctx context.Context) string {
	e.t.Helper()

	var buffer bytes.Buffer
	err := e.doMatchWithDeadline(ctx, "ReadLine", func(rd *bufio.Reader) error {
		for {
			r, _, err := rd.ReadRune()
			if err != nil {
				return err
			}
			if r == '\n' {
				return nil
			}
			if r == '\r' {
				// Peek the next rune to see if it's an LF and then consume
				// it.

				// Unicode code points can be up to 4 bytes, but the
				// ones we're looking for are only 1 byte.
				b, _ := rd.Peek(1)
				if len(b) == 0 {
					return nil
				}

				r, _ = utf8.DecodeRune(b)
				if r == '\n' {
					_, _, err = rd.ReadRune()
					if err != nil {
						return err
					}
				}

				return nil
			}

			_, err = buffer.WriteRune(r)
			if err != nil {
				return err
			}
		}
	})
	if err != nil {
		e.fatalf("read error", "%v (wanted newline; got %q)", err, buffer.String())
		return ""
	}
	e.Logf("matched newline = %q", buffer.String())
	return buffer.String()
}

func (e *Expecter) ReadAll() []byte {
	e.t.Helper()
	return e.out.ReadAll()
}

func (e *Expecter) doMatchWithDeadline(ctx context.Context, name string, fn func(*bufio.Reader) error) error {
	e.t.Helper()

	// A timeout is mandatory, caller can decide by passing a context
	// that times out.
	if _, ok := ctx.Deadline(); !ok {
		timeout := testutil.WaitMedium
		e.Logf("%s ctx has no deadline, using %s", name, timeout)
		var cancel context.CancelFunc
		//nolint:gocritic // Rule guard doesn't detect that we're using testutil.Wait*.
		ctx, cancel = context.WithTimeout(ctx, timeout)
		defer cancel()
	}

	match := make(chan error, 1)
	go func() {
		defer close(match)
		match <- fn(e.runeReader)
	}()
	select {
	case err := <-match:
		return err
	case <-ctx.Done():
		// Ensure goroutine is cleaned up before test exit, do not call
		// (*outExpecter).close here to let the caller decide.
		_ = e.out.Close()
		<-match

		return xerrors.Errorf("match deadline exceeded: %w", ctx.Err())
	}
}

func (e *Expecter) Logf(format string, args ...interface{}) {
	e.t.Helper()

	// Match regular logger timestamp format, we seem to be logging in
	// UTC in other places as well, so match here.
	e.t.Logf("%s: %s: %s", time.Now().UTC().Format("2006-01-02 15:04:05.000"), e.name.Load(), fmt.Sprintf(format, args...))
}

func (e *Expecter) fatalf(reason string, format string, args ...interface{}) {
	e.t.Helper()

	// Ensure the message is part of the normal log stream before
	// failing the test.
	e.Logf("%s: %s", reason, fmt.Sprintf(format, args...))

	require.FailNowf(e.t, reason, format, args...)
}