package editor

import (
	"log"
	"sync"
	"time"

	"pad/internal/browser"
	"pad/internal/io/pool"
	"pad/internal/io/pool/mock"
	"pad/internal/io/pool/types"
	"pad/internal/ui"
)

// ConfigEvent represents a window configuration change (resize, orientation).
// PixelWidth and PixelHeight are the raw pixel dimensions from Gio.
type ConfigEvent struct {
	PixelWidth  int
	PixelHeight int
}

// ScaleEvent represents a metric change (HiDPI scale factor).
type ScaleEvent struct {
	Scale float32
}

// ConfigUpdate is a common interface for all configuration updates.
// Both ConfigEvent and ScaleEvent implement this interface.
type ConfigUpdate interface {
	apply(*State)
}

func (e ConfigEvent) apply(s *State) {
	s.PixelWidth = e.PixelWidth
	s.PixelHeight = e.PixelHeight
}

func (e ScaleEvent) apply(s *State) {
	s.SetScale(e.Scale)
}

// ResultEvent represents a completed async task result.
type ResultEvent struct {
	// Future: add result fields here
}

// Logic runs the logic goroutine and provides channels for communication.
//
// Single-owner invariant (architecture.md §1): the logic goroutine is the
// sole reader/writer of l.state. Every other goroutine talks to it through
// the channels below. The only exception is Inspect, a test-only request
// channel whose fn still executes on the owner.
type Logic struct {
	state            *State
	browserManager   *browser.BrowserManager
	configChan       chan ConfigUpdate
	frameChan        chan Frame // frames carry the view-state snapshot
	inputChan        chan []ui.InputEvent
	layoutChan       chan ui.GlyphLayout
	resultChan       chan ResultEvent
	searchQueryChan  chan string
	openFileChan     chan string
	retryChan        chan string // auto-save retries
	autosaveChan     chan struct{} // auto-save debounce ticks (timer -> owner)
	inspectChan      chan *inspectReq
	workerPool       *pool.WorkerPool
	mockFS           pool.FileSystem
	done             chan struct{}
	exitWg           sync.WaitGroup
	saveTimer        *time.Timer // auto-save debounce timer; non-nil while pending
}

// NewLogic creates a new Logic instance, accepting an optional mockFS.
func NewLogic(mfs pool.FileSystem, path string, openfunc func(string)) *Logic {
	state := NewState()
	TheState = state
	TheState.open = openfunc
	ui.OpenFile = openfunc

	// Initialize mock filesystem if nil
	mockFS := mfs
	if mockFS == nil {
		mockFS = mock.NewFileSystem()
		populateMockFileSystem(mockFS)
	}

	// Initialize worker pool
	wp := pool.NewWorkerPool(8) // Increased worker pool size to 8
	wp.Start()

	state.Browser.CurrentPath = path
	bm, _ := browser.NewBrowserManager(&state.Browser, wp, mockFS)

	TheLogic = &Logic{
		state:           state,
		browserManager:  bm,
		configChan:      make(chan ConfigUpdate),
		frameChan:       make(chan Frame, 1),
		inputChan:       make(chan []ui.InputEvent),
		layoutChan:      make(chan ui.GlyphLayout),
		resultChan:      make(chan ResultEvent),
		searchQueryChan: make(chan string),
		openFileChan:    make(chan string),
		retryChan:       make(chan string, 1), // Buffered channel
		autosaveChan:    make(chan struct{}),
		inspectChan:     make(chan *inspectReq),
		workerPool:      wp,
		mockFS:          mockFS,
		done:            make(chan struct{}),
	}
	return TheLogic
}

// ConfigChan returns the unified config channel for the logic goroutine.
// Accepts ConfigEvent (size) and ScaleEvent (scale factor).
func (l *Logic) ConfigChan() chan<- ConfigUpdate {
	return l.configChan
}

// FrameChan returns the frame channel for the logic goroutine.
func (l *Logic) FrameChan() <-chan Frame {
	return l.frameChan
}



// InputChan returns the input channel for the logic goroutine.
func (l *Logic) InputChan() chan<- []ui.InputEvent {
	return l.inputChan
}

// LayoutChan returns the glyph layout feedback channel.
func (l *Logic) LayoutChan() chan<- ui.GlyphLayout {
	return l.layoutChan
}

// ResultChan returns the result channel for the logic goroutine.
func (l *Logic) ResultChan() chan<- ResultEvent {
	return l.resultChan
}

// SearchQueryChan returns the search query channel for the logic goroutine.
// The main goroutine sends updated search text here when it detects a change.
func (l *Logic) SearchQueryChan() chan<- string {
	return l.searchQueryChan
}

var TheState *State
var TheLogic *Logic

// Run runs the logic goroutine loop.
func (l *Logic) Run() {
	l.exitWg.Add(1)
	defer l.exitWg.Done()

	// Dispatch initial directory index build on startup
	log.Printf("Logic: Dispatching BuildIndexTask")
	l.workerPool.Dispatch(pool.NewBuildIndexTask(l.state.Browser.CurrentPath, l.mockFS))

	for {
		select {
		case <-l.done:
			return
		case update := <-l.configChan:
			log.Printf("Logic: ConfigEvent")
			update.apply(l.state)
			l.frameChan <- l.frameOf(l.state.layout(l.browserManager))
		case layout := <-l.layoutChan:
			// Store the full GlyphLayout on editor state.
			// Derive LastLineY from it for scroll clamping.
			l.state.Editor.GlyphLayout = layout
			log.Printf("LOGIC received GlyphLayout: ByteOffsets=%d, VisualLineStarts=%d", len(layout.ByteOffsets), len(layout.VisualLineStarts))
			var derivedLastLineY ui.Dp
			if len(layout.Y) > 0 {
				derivedLastLineY = layout.Y[len(layout.Y)-1]
			}
			if derivedLastLineY != l.state.LastLineY {
				l.state.LastLineY = derivedLastLineY
				l.frameChan <- l.frameOf(l.state.layout(l.browserManager))
			}
		case events := <-l.inputChan:
			log.Printf("Logic: InputEvents")
			for _, evt := range events {
				evt.Handler(evt.Data)
			}
			l.frameChan <- l.frameOf(l.state.layout(l.browserManager))
		case query := <-l.searchQueryChan:
			log.Printf("Logic: SearchQuery")
			if query != l.state.Browser.Query {
				l.state.Browser.Query = query
				if l.state.page == BrowserPage {
					browser.HandleSearch(&l.state.Browser, query)
				}
			}
			l.frameChan <- l.frameOf(l.state.layout(l.browserManager))
		case path := <-l.openFileChan:
			log.Printf("Logic: OpenFileChan %s", path)
			// Create chunked buffer for virtual scrolling
			chunkSize := DefaultChunkSize
			cb := NewChunkedBuffer(path, chunkSize, l.mockFS, "")
			cb.SetWorkerPool(l.workerPool)
			TheState.Editor.ChunkedBuffer = cb

			// Dispatch stat task to get file size
			l.workerPool.Dispatch(pool.NewStatFileTask(path, l.mockFS))
		case filename := <-l.retryChan:
			log.Printf("Logic: Retrying save for %s", filename)
			if filename == l.state.Editor.Filename {
				// Reconstruct full content from chunked buffer for saving
				content, ok := l.fullContentBytes()
				if !ok {
					break
				}
				l.workerPool.DispatchNonBlocking(
					pool.NewWriteFileTask(filename, content, l.mockFS),
				)
			}
		case <-l.autosaveChan:
			// Auto-save debounce tick. The timer goroutine only sent a token;
			// the owner reconstructs content and dispatches the write.
			l.saveTimer = nil
			if l.state.Editor.Filename == "" {
				break
			}
			content, ok := l.fullContentBytes()
			if !ok {
				break
			}
			log.Printf("Logic: Dispatching WriteFileTask for %s, content len=%d", l.state.Editor.Filename, len(content))
			l.workerPool.DispatchNonBlocking(
				pool.NewWriteFileTask(l.state.Editor.Filename, content, l.mockFS),
			)
		case req := <-l.inspectChan:
			// Test-only: fn runs on the owner, preserving single ownership.
			req.resp <- req.fn(l.state)
		case res := <-l.workerPool.ResultChan():
			l.handleWorkerResult(res)
		case <-l.resultChan:
			l.frameChan <- l.frameOf(l.state.layout(l.browserManager))
		}
	}
}

// fullContentBytes reconstructs the full file content from the chunked
// buffer (or the deprecated full Buffer). Returns ok=false on error.
// Must be called on the logic goroutine.
func (l *Logic) fullContentBytes() ([]byte, bool) {
	if l.state.Editor.ChunkedBuffer != nil {
		fullContent, err := l.state.Editor.ChunkedBuffer.FullContent()
		if err != nil {
			log.Printf("Error reconstructing full content: %v", err)
			return nil, false
		}
		return []byte(fullContent), true
	}
	return []byte(l.state.Editor.Buffer), true
}

// markDirty triggers the auto-save debounce timer.
// Must be called on the logic goroutine.
//
// The timer callback runs on a timer goroutine and only sends a token on
// autosaveChan; the owner (Run loop) does all state reads and the worker
// dispatch. This keeps the timer goroutine out of state (architecture.md §1).
func (l *Logic) markDirty() {
	if l.state.Editor.Filename == "" {
		return
	}
	l.state.Editor.fileVersion[l.state.Editor.Filename]++

	// 1s debounce
	if l.saveTimer != nil {
		l.saveTimer.Stop()
	}
	l.saveTimer = time.AfterFunc(1*time.Second, func() {
		l.autosaveChan <- struct{}{}
	})
}

// handleWorkerResult processes results from the worker pool.
func (l *Logic) handleWorkerResult(res pool.Result) {
	if res.IsBrowserResult() {
		l.browserManager.HandleResult(res)
	} else if res.TaskType == pool.TypeReadFile {
		log.Printf("Logic: TypeReadFile result success=%v", res.Success)
		if res.Success {
			if content, ok := res.Data.([]byte); ok {
				if l.state.Editor.ChunkedBuffer != nil {
					// Always populate the chunked buffer and ensure its size is set.
					l.state.Editor.ChunkedBuffer.SetFileSize(int64(len(content)))
					l.state.Editor.ChunkedBuffer.Insert(0, string(content))
					// Also update the Buffer field for backward compatibility and for tests checking it.
					l.state.Editor.Buffer = string(content)
				} else {
					// Fallback: populate the deprecated Buffer field
					l.state.Editor.Buffer = string(content)
				}
			}
		}
	} else if res.TaskType == pool.TypeReadChunk {
		if cb := l.state.Editor.ChunkedBuffer; cb != nil {
			delete(cb.loadingChunks, res.ChunkIdx) // Use explicit ChunkIdx field

			if res.Success {
				if chunk, ok := res.Data.([]byte); ok {
					cb.chunks[res.ChunkIdx] = chunk
					log.Printf("Logic: Loaded chunk %d for %s (%d bytes)", res.ChunkIdx, res.FilePath, len(chunk))
				}
			} else {
				log.Printf("Logic: ReadChunkTask failed for %s chunk %d: %v", res.FilePath, res.ChunkIdx, res.Error)
			}
		}
	} else if res.TaskType == pool.TypeStatFile {
		log.Printf("Logic: TypeStatFile result success=%v", res.Success)
		if res.Success {
			if stat, ok := res.Data.(*pool.FileStat); ok {
				if l.state.Editor.ChunkedBuffer != nil {
					l.state.Editor.ChunkedBuffer.SetFileSize(stat.Size)
					// Load the chunk containing the cursor (position 0 at open)
					l.state.Editor.ChunkedBuffer.LoadChunk(0)
					// Prefetch adjacent chunks
					l.state.Editor.ChunkedBuffer.Prefetch(0, 1)
					// Dispatch line index build task
					l.workerPool.Dispatch(pool.NewBuildLineIndexTask(l.state.Editor.Filename, l.mockFS))
				}
			}
		}
	} else if res.TaskType == pool.TypeBuildLineIndex {
		log.Printf("Logic: TypeBuildLineIndex result success=%v", res.Success)
		if res.Success {
			if idx, ok := res.Data.(*types.LineIndex); ok {
				if l.state.Editor.ChunkedBuffer != nil {
					l.state.Editor.ChunkedBuffer.LineIndex = idx
					log.Printf("Logic: LineIndex built with %d lines", idx.LineCount())
				}
			}
		}
	} else if res.TaskType == pool.TypeWriteFile {
		if res.Success {
			l.state.Editor.lastWriteVersion[res.FilePath] = l.state.Editor.fileVersion[res.FilePath]
			l.state.Editor.SetWriteFailed(res.FilePath, false)
		} else {
			log.Printf("Auto-save failed for %s: %v", res.FilePath, res.Error)
			l.state.Editor.SetWriteFailed(res.FilePath, true)

			// Trigger retry logic: exponential backoff
			attempts := l.state.Editor.IncrementRetryAttempts(res.FilePath)
			// Simple backoff: 1s, 2s, 4s, 8s... max 30s
			delay := time.Duration(1<<(attempts-1)) * time.Second
			if delay > 30*time.Second {
				delay = 30 * time.Second
			}

			filename := res.FilePath
			log.Printf("Scheduling retry for %s in %v (attempt %d)", filename, delay, attempts)
			time.AfterFunc(delay, func() {
				log.Printf("Firing retry for %s", filename)
				l.retryChan <- filename
			})
		}
	}
	l.frameChan <- l.frameOf(l.state.layout(l.browserManager))
}

// applyBuildIndexResult applies a completed BuildIndexTask result to browser state.
func (l *Logic) applyBuildIndexResult(res pool.Result) {
	// Delegated to browserManager
}

// applyLoadPagesResult applies a completed LoadPagesTask result to browser state.
func (l *Logic) applyLoadPagesResult(res pool.Result) {
	// Delegated to browserManager
}

// applyReadDirResult applies a completed ReadDirTask result to browser state.
func (l *Logic) applyReadDirResult(res pool.Result) {
	// Delegated to browserManager
}

// State returns the current state.
func (l *Logic) State() *State {
	return l.state
}

// PruneMaps removes old entries to keep memory usage bounded.
// Keeps entries for the last 1000 files.
func (l *Logic) PruneMaps() {
	if len(l.state.Editor.fileVersion) <= 1000 {
		return
	}

	// Simply clear the maps for now. A true LRU would require 
	// tracking access times.
	l.state.Editor.fileVersion = make(map[string]int)
	l.state.Editor.lastWriteVersion = make(map[string]int)
	l.state.Editor.writeFailed = make(map[string]bool)
	l.state.Editor.retryAttempts = make(map[string]int)
}

// Done signals the logic goroutine to stop.
func (l *Logic) Done() {
	close(l.done)
}

// WaitForExit blocks until the logic goroutine has fully stopped. After
// this returns, the caller (e.g. Shutdown) may touch state single-threaded.
func (l *Logic) WaitForExit() {
	l.exitWg.Wait()
}

// FlushAll triggers synchronous writes for all dirty files.
//
// Must be called either from the logic goroutine (e.g. via GoToBrowser) or
// after the logic goroutine has fully stopped (Shutdown). It touches state
// directly, so it must never run concurrently with Run (single-owner
// invariant, architecture.md §1).
func (l *Logic) FlushAll() {
	for filename := range l.state.Editor.fileVersion {
		if l.state.Editor.IsDirty() && l.state.Editor.Filename == filename {
			content, ok := l.fullContentBytes()
			if !ok {
				continue
			}
			// In a real app, this would be a blocking call to the FS
			l.mockFS.WriteFileAtomic(filename, content)
			l.state.Editor.lastWriteVersion[filename] = l.state.Editor.fileVersion[filename]
		}
	}
}

// Shutdown gracefully shuts down the logic goroutine and worker pool.
// The logic goroutine is stopped FIRST so that FlushAll can touch state
// single-threaded; the worker pool is stopped last so in-flight results
// still have a reader until then.
func (l *Logic) Shutdown() {
	l.Done()
	l.WaitForExit()
	l.FlushAll()
	l.workerPool.Stop()
}