package main

import (
	"flag"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"gioui.org/app"
	"gioui.org/font/gofont"
	"gioui.org/io/clipboard"
	"gioui.org/io/key"
	"gioui.org/io/transfer"
	"gioui.org/op"
	"gioui.org/text"
	"gioui.org/unit"
	"gioui.org/widget"

	"pad/internal/editor"
	"pad/internal/io/pool/real"
	"pad/internal/perf"
	"pad/internal/ui"
)

func main() {
	go func() {
		w := new(app.Window)
		w.Option(app.Title("Pad"))
		w.Option(app.Size(unit.Dp(390), unit.Dp(844)))
		if err := run(w); err != nil {
			log.Fatal(err)
		}
		os.Exit(0)
	}()
	app.Main()
}

func run(w *app.Window) error {
	var ops op.Ops
	shaper := text.NewShaper(text.WithCollection(gofont.Collection()))

	// Determine root directory for real filesystem
	rootDir := flag.String("root", startpath, "root directory for the filesystem")
	flag.Parse()

	// Initialize the real filesystem rooted at the system root "/"
	// so that the browser can navigate the entire system.
	fs := real.NewRealFileSystem("/")

	// Get the absolute path of the startup directory
	startAbs, err := filepath.Abs(*rootDir)
	if err != nil {
		startAbs = *rootDir
	}
	log.Printf("using filesystem at / (startup directory: %s)", startAbs)

	logic := editor.NewLogic(fs, startAbs, OpenFile)
	renderer := ui.New(ui.Theme{FontSize: 14}, shaper)

	// In-app frame profiler (default off). Enabled by the presence of a marker
	// file so the shipping APK needs no rebuild to toggle profiling. When on,
	// it records logic-frame cadence plus scroll/visible-range context to a CSV
	// and logs rolling percentiles; it also enables the scroll-jump debug poller.
	const perfDir = "/storage/emulated/0/PadPerf"
	var prof *perf.Profiler
	var perfOn bool
	var presentN int
	var presentStart time.Time
	// shiftDown tracks the hardware shift key on the MAIN goroutine.
	// On Android Gio's JNI bridge drops modifier state (GioView.onKeyEvent
	// never reads event.getMetaState), so key.Event.Modifiers is always 0 and
	// shift+arrow is indistinguishable from a plain arrow. Gio does deliver
	// the NameShift press/release as plain key.Events, so we track them here
	// and attach the state to the ui.KeyEvent we forward.
	var shiftDown bool
	if _, err := os.Stat(filepath.Join(perfDir, "enable")); err == nil {
		prof = perf.New(true, perfDir, "logic_frames.csv")
		editor.PerfRecord = func(rec editor.ProbeRecord) {
			prof.Record(perf.Ctx{
				Page:        rec.Page,
				ScrollDP:    rec.ScrollDP,
				MaxScrollDP: rec.MaxScrollDP,
				TotalLines:  rec.TotalLines,
				VisStart:    rec.VisStart,
				VisEnd:      rec.VisEnd,
			})
		}
		logic.EnableDebugCmdPoll(perfDir)
		perfOn = true
		log.Printf("PERF: enabled (dir=%s)", perfDir)
	}

	// The search bar's widget.Editor is owned by the MAIN goroutine: Gio
	// mutates it during draw, and the logic goroutine must never touch it
	// (architecture.md §1). Its text is forwarded to the logic goroutine via
	// SearchQueryChan; the logic only stores the result in Browser.Query.
	var searchEditor widget.Editor
	renderer.RegisterGioEditor("search_bar", &searchEditor)

	// Clipboard plumbing (architecture.md §6.3): the logic goroutine only
	// REQUESTS clipboard operations through channels (copy/cut write, paste
	// read); the main goroutine executes the Gio ops during a frame and
	// forwards the read result back. clipTag tags the read so its
	// transfer.DataEvent can be matched. A nil clipboard (e.g. a headless
	// test) simply never completes a read.
	var clipTag = struct{}{}

	// frame is the frame-receiver-stored handoff (architecture.md §2.2/§9):
	// the ONLY data the main goroutine reads from the logic side.
	var mu sync.Mutex
	var frame editor.Frame

	go frameReceiver(w, &mu, &frame, logic.FrameChan())
	go logic.Run()

	for {
		switch e := w.Event().(type) {
		case app.DestroyEvent:
			if prof != nil {
				prof.Stop()
			}
			logic.Shutdown()
			return e.Err
		case app.ConfigEvent:
			// ConfigEvent: raw pixel dimensions only.
			logic.ConfigChan() <- editor.ConfigEvent{
				PixelWidth:  e.Config.Size.X,
				PixelHeight: e.Config.Size.Y,
			}
		case app.FrameEvent:
			if perfOn {
				presentN++
				if presentStart.IsZero() {
					presentStart = time.Now()
				}
				if time.Since(presentStart) >= 2*time.Second {
					dt := time.Since(presentStart).Seconds()
					log.Printf("PERF-PRESENT frames=%d fps=%.1f", presentN, float64(presentN)/dt)
					presentN = 0
					presentStart = time.Time{}
				}
			}
			gtx := app.NewContext(&ops, e)
			newScale := gtx.Metric.PxPerDp
			// User font-size setting: the shaper draws baselines in sp, so the
			// rendered line pitch in density-dp is scaled by this factor. Logic
			// bookkeeping (tap mapping, window start, scroll clamp) must follow
			// it (EffectiveLineHeight).
			newFontScale := float32(1)
			if gtx.Metric.PxPerDp > 0 && gtx.Metric.PxPerSp > 0 {
				newFontScale = gtx.Metric.PxPerSp / gtx.Metric.PxPerDp
			}
			// Clipboard: forward a read result from an earlier frame to the
			// logic goroutine (one DataEvent per ReadCmd).
			for {
				evt, ok := gtx.Event(transfer.TargetFilter{Target: clipTag, Type: "application/text"})
				if !ok {
					break
				}
				if de, ok := evt.(transfer.DataEvent); ok {
					body := de.Open()
					data, rerr := io.ReadAll(body)
					body.Close()
					if rerr == nil {
						logic.PasteChan() <- string(data)
					}
				}
			}
			// Clipboard: a copy/cut write requested by the logic goroutine.
			select {
			case t := <-logic.ClipboardSetChan():
				gtx.Execute(clipboard.WriteCmd{Type: "application/text", Data: io.NopCloser(strings.NewReader(t))})
			default:
			}
			// Clipboard: a paste request (one ReadCmd per request; the result
			// arrives as a DataEvent on a later frame). On Android the read is
			// synchronous and the resulting DataEvent is queued during this
			// frame's op flush — but a queued DataEvent schedules no wakeup of
			// its own, so invalidate to guarantee a follow-up frame in which
			// the loop above can consume it.
			select {
			case <-logic.PasteReqChan():
				gtx.Execute(clipboard.ReadCmd{Tag: clipTag})
				w.Invalidate()
			default:
			}
			// Read ONLY the frame-receiver-stored snapshot; the main goroutine
			// never touches logic State (architecture.md §1).
			mu.Lock()
			curScale := frame.Scale
			if curScale <= 0 {
				curScale = 1 // no frame yet
			}
			curFontScale := frame.FontScale // 0 until the logic has the value
			renderer.Draw(gtx, frame.Elems, curScale)
			glyphLayout := renderer.GlyphLayout()
			// Send search query update to the logic goroutine when it changes.
			// The logic goroutine handles filtering and triggers a new frame.
			newQuery := searchEditor.Text()
			sendQuery := newQuery != frame.Query
			events := renderer.CheckGestures(e.Source, gtx.Metric)
			// Keep frames flowing while a long press is pending: a stationary
			// finger generates no pointer events, so without this the window
			// would sleep and the long-press threshold would never be reached.
			if renderer.PendingLongPress() {
				w.Invalidate()
			}

			// Gather key events
			focusedID := frame.FocusedElementID
			if focusedID == "" {
				// No focused input: drop any stale shift state (a release event
				// for a key held across focus loss may never arrive).
				shiftDown = false
			}
			if focusedID != "" {
				if reg, ok := renderer.Keys[focusedID]; ok {
					// Use key.Filter to only receive events destined for the focused element.
					// We need both Key events (for arrow keys) and Edit events (for text input).
					// In Gio, key.Filter covers key presses, while key.FocusFilter covers
					// focus and text edit events.
					//
					// On mobile the window layer wraps plain arrow-key PRESSES in
					// input.SystemEvent (it wants to use them for focus navigation) and
					// such events match only filters that name the key explicitly. Querying
					// the four arrow names below therefore (a) makes the presses deliverable
					// and (b) suppresses the focus-move side effect: a matched event makes
					// WakeupTime report handled, which skips the window's moveFocus call.
					for {
						// Filter for key events and focus/edit events targeted at focusedID
						evt, ok := gtx.Event(
							key.Filter{Focus: focusedID},
							key.Filter{Focus: focusedID, Name: key.NameLeftArrow},
							key.Filter{Focus: focusedID, Name: key.NameRightArrow},
							key.Filter{Focus: focusedID, Name: key.NameUpArrow},
							key.Filter{Focus: focusedID, Name: key.NameDownArrow},
							key.FocusFilter{Target: focusedID},
						)
						if !ok {
							break
						}
						switch k := evt.(type) {
						case key.Event:
							if k.Name == key.NameShift {
								// Track shift; never forward it as a content key.
								shiftDown = k.State == key.Press
								continue
							}
							if k.State == key.Press {
								// ui.KeyEvent carries modifier state so handlers
								// can distinguish shift+arrow (extend selection)
								// from plain arrow (move cursor). On Android the
								// Modifiers field is always empty, hence the shiftDown OR.
								events = append(events, ui.InputEvent{
									Handler: reg.Handler,
									Data: ui.KeyEvent{
										Name:  k.Name,
										Shift: k.Modifiers.Contain(key.ModShift) || shiftDown,
									},
								})
							}
						case key.EditEvent:
							events = append(events, ui.InputEvent{
								Handler: reg.Handler,
								Data:    k,
							})
						case key.SnippetEvent:
							// Handle snippet event if necessary, or ignore
						default:
							log.Printf("unexpected event type: %T", k)
						}
					}
				}
			}
			e.Frame(&ops)
			mu.Unlock()
			if newScale != curScale || newFontScale != curFontScale {
				logic.ConfigChan() <- editor.ScaleEvent{Scale: newScale, FontScale: newFontScale}
			}
			if len(events) > 0 {
				logic.InputChan() <- events
			}
			if sendQuery {
				logic.SearchQueryChan() <- newQuery
			}
			logic.LayoutChan() <- ui.LayoutFeedback{
				GlyphLayout:     glyphLayout,
				WindowText:      frame.WindowText,
				WindowStartByte: frame.WindowStartByte,
				WindowStartLine: frame.WindowStartLine,
				EditSeq:         frame.EditSeq,
			}
		default:
			handleEvent(e)
		}
	}
}

func frameReceiver(w *app.Window, mu *sync.Mutex, frame *editor.Frame, frameChan <-chan editor.Frame) {
	for {
		f := <-frameChan
		mu.Lock()
		*frame = f
		w.Invalidate()
		mu.Unlock()
	}
}