package e2e

import (
	"fmt"
	"sync"
	"time"

	"pad/internal/editor"
	"pad/internal/ui"
)

var errInspectTimeout = fmt.Errorf("e2e: inspect timed out waiting for the logic goroutine")

// Harness orchestrates the test environment for e2e tests.
type Harness struct {
	logic             *editor.Logic
	capture           *FrameCapture
	logicWg           sync.WaitGroup
	frameReceiverDone chan struct{}
	wg                sync.WaitGroup
	started           bool
}

// HarnessOption configures the test harness.
type HarnessOption func(*Harness)

// NewHarness creates a test harness with the given options.
func NewHarness(opts ...HarnessOption) *Harness {
	h := &Harness{
		logic:             editor.NewLogic(nil, "/", func(string) {}), // no-op openfunc (matches impl_other.go)
		capture:           NewFrameCapture(),
		frameReceiverDone: make(chan struct{}),
	}

	for _, opt := range opts {
		opt(h)
	}

	return h
}

// Run starts the logic goroutine and frame capture.
// It must be called at most once: two Run loops on the same channels and
// state would race (NewHarnessWithDefaults already calls it).
func (h *Harness) Run() {
	if h.started {
		panic("e2e: Harness.Run called twice")
	}
	h.started = true
	h.logicWg.Add(1)
	h.wg.Add(1)
	go func() {
		defer h.wg.Done()
		defer h.logicWg.Done()
		h.logic.Run()
	}()

	h.wg.Add(1)
	go func() {
		defer h.wg.Done()
		for {
			select {
			case frame := <-h.logic.FrameChan():
				h.capture.CaptureFrame(frame.Elems)
			case <-h.frameReceiverDone:
				return
			}
		}
	}()
}

// SendConfig simulates a window config event (resize).
func (h *Harness) SendConfig(width, height int) {
	h.logic.ConfigChan() <- editor.ConfigEvent{
		PixelWidth:  width,
		PixelHeight: height,
	}
}

// SendScale simulates a scale factor change.
func (h *Harness) SendScale(scale float32) {
	h.logic.ConfigChan() <- editor.ScaleEvent{Scale: scale}
}

// SendInput simulates user input events.
func (h *Harness) SendInput(events []ui.InputEvent) {
	h.logic.InputChan() <- events
}

// SendSearchQuery simulates a search query update.
func (h *Harness) SendSearchQuery(query string) {
	h.logic.SearchQueryChan() <- query
}

// GetFrames returns all captured frames.
func (h *Harness) GetFrames() [][]ui.Element {
	return h.capture.GetFrames()
}

// FrameCount returns the number of frames captured so far.
func (h *Harness) FrameCount() int {
	return h.capture.FrameCount()
}

// Inspect runs fn on the logic goroutine and returns its result.
// This is the ONLY sanctioned way for a test to read or write state: the fn
// executes on the owner, preserving the single-owner invariant
// (architecture.md §1). fn must not block on sends to logic channels.
func (h *Harness) Inspect(fn func(st *editor.State) any) (any, error) {
	v, ok := h.logic.Inspect(fn)
	if !ok {
		return nil, errInspectTimeout
	}
	return v, nil
}

// WithState runs fn on the logic goroutine for state setup or mutation.
func (h *Harness) WithState(fn func(st *editor.State)) error {
	_, err := h.Inspect(func(st *editor.State) any {
		fn(st)
		return nil
	})
	return err
}

// FileLoaded reports whether the active file's chunked buffer has loaded
// content (owner-side check).
func (h *Harness) FileLoaded() (bool, error) {
	v, err := h.Inspect(func(st *editor.State) any {
		cb := st.Editor.ChunkedBuffer
		return cb != nil && cb.FileLen() > 0
	})
	if err != nil {
		return false, err
	}
	return v.(bool), nil
}

// FullContent returns the active file's full content (owner-side).
func (h *Harness) FullContent() (string, error) {
	v, err := h.Inspect(func(st *editor.State) any {
		if st.Editor.ChunkedBuffer != nil {
			full, err := st.Editor.ChunkedBuffer.FullContent()
			if err != nil {
				return ""
			}
			return full
		}
		return st.Editor.Buffer
	})
	if err != nil {
		return "", err
	}
	return v.(string), nil
}

// CursorPosition returns the editor cursor position (owner-side).
func (h *Harness) CursorPosition() (int, error) {
	v, err := h.Inspect(func(st *editor.State) any { return st.Editor.CursorPosition })
	if err != nil {
		return 0, err
	}
	return v.(int), nil
}

// WaitForFrameCount blocks until at least N frames are captured.
func (h *Harness) WaitForFrameCount(count int, timeout time.Duration) ([][]ui.Element, error) {
	return h.capture.WaitForFrameCount(count, timeout)
}

// WaitForFrame blocks until at least one frame is captured.
func (h *Harness) WaitForFrame(timeout time.Duration) ([][]ui.Element, error) {
	return h.capture.WaitForFrame(timeout)
}

// Cleanup stops all goroutines.
func (h *Harness) Cleanup() {
	// 1. Signal logic to stop sending frames
	h.logic.Done()

	// 2. Wait for logic goroutine to fully exit (no more frameChan sends)
	h.logicWg.Wait()

	// 3. Now safe to stop the frame receiver
	close(h.frameReceiverDone)

	// 4. Wait for frame receiver to finish
	h.wg.Wait()

	h.capture.Close()
}

// DefaultTimeout is the default timeout for waiting operations.
const DefaultTimeout = 5 * time.Second