package main

import (
	"encoding/json"
	"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)
	activeLogic = logic
	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)

	// The find bar's (in-file search) widget.Editor is main-owned the same
	// way; its text is forwarded via FindQueryChan (editor.findSetQuery).
	var findEditor widget.Editor
	renderer.RegisterGioEditor("find_bar", &findEditor)

	// Relaunch state restoration (spec §7): a tiny JSON file holds the last
	// file, cursor, scroll, selection and find bar state. The cmd layer owns
	// the file (sessionFilePath, per platform); the logic layer owns the
	// snapshot (editor.SessionState) and calls the saver rate-limited and at
	// Shutdown. Restoring re-opens the last file straight into the editor.
	sessPath := sessionFilePath()
	logic.SetSessionSaver(newSessionSaver(sessPath))
	if sess, ok := loadSession(sessPath); ok {
		log.Printf("restoring session: file=%s cursor=%d scroll=%v find=%q", sess.File, sess.Cursor, sess.Scroll, sess.FindQuery)
		logic.BeginRestore(sess)
		// The find bar's input is a main-owned widget and the input source of
		// truth: seed it with the restored query so its first frame matches
		// the logic-side query (an empty widget would forward "" and clear
		// the restored query).
		if sess.FindQuery != "" {
			findEditor.SetText(sess.FindQuery)
		}
	}

	// 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()

	// lastExcl tracks the selection-handle grab boxes last sent to
	// SetGestureExclusions (Android: keeps the system back gesture from
	// stealing drags that start on an edge handle). Only the JNI call when
	// the set changes — the rects move every frame while a selection is
	// visible/scrolling, but identical repeats are skipped.
	var lastExcl [][4]int
	// findBarFocused tracks whether the previous frame focused the find bar's
	// main-owned input, so main hands key focus to it exactly once per open
	// (see the focus handoff below).
	var findBarFocused bool
	// lastFindClearSeq is the FindClearSeq value whose wipe has already been
	// applied to the main-owned find input (edge-triggered, see
	// Frame.FindClearSeq).
	var lastFindClearSeq int
	// lastFrameW/H hold the previous FrameEvent's window size (px); 0 = no
	// frame yet. Used to spot shrink frames (see ZeroWheelScroll below).
	var lastFrameW, lastFrameH int

	for {
		e := w.Event()
		switch e := e.(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
			// App-local pinch font scale for the editor text (1.0 = default).
			renderer.SetAppFontScale(frame.AppFontScale)
			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
			// Mirror each NEW find-clear (the bar's X button) into the main-
			// owned widget input exactly once. Edge-triggered on ClearSeq, NOT
			// "FindQuery==\"\" && widget has text": that level check also fired on
			// stale frames between the user's typing and the logic storing it,
			// wiping the input while typing.
			if frame.FindClearSeq > lastFindClearSeq {
				lastFindClearSeq = frame.FindClearSeq
				findEditor.SetText("")
				w.Invalidate()
			}
			newFind := findEditor.Text()
			sendFind := newFind != frame.FindQuery
			// On a frame that shrinks the window (the IME opening under
			// adjustResize), Gio's window synthesizes a scroll-to-focus
			// pointer.Scroll via RevealFocus — it reads the focused field's
			// stale pre-resize bounds and nudges the editor content. Flag the
			// frame so CheckGestures drains that one synthetic event before the
			// scroll gesture consumes it (Renderer.ZeroWheelScroll); finger
			// scroll and the flinger are unaffected, and normal frames are
			// untouched.
			renderer.ZeroWheelScroll = lastFrameH > 0 &&
				(e.Size.Y < lastFrameH || e.Size.X < lastFrameW)
			lastFrameW, lastFrameH = e.Size.X, e.Size.Y
			events := renderer.CheckGestures(e.Source, gtx.Metric)
			renderer.ZeroWheelScroll = false
			// 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()
			}
			// Selection-handle system-gesture exclusions (Android): forward the
			// frame's handle grab boxes when they changed. Runs on the UI
			// thread (the frame pump is), as View methods require.
			if excl := renderer.GestureExclusions(); !exclEqual(excl, lastExcl) {
				lastExcl = excl
				SetGestureExclusions(excl)
			}

			// Gather key events
			focusedID := frame.FocusedElementID
			// Hand key focus to the find bar's main-owned input the moment the
			// find bar opens: the search-icon tap never touches the widget, and
			// widget.Editor only grabs key focus on its own click (gioui.org/
			// widget/editor.go). The widget's FocusEvent handler raises the soft
			// keyboard on focus gain, so the keyboard follows automatically. On
			// the inverse transition the editor's TextField re-issues its own
			// key.FocusCmd (the renderer clears the focus dedup on frames where
			// no logic field is focused), so nothing is needed on close.
			if focusedID == "find_bar" && !findBarFocused {
				gtx.Execute(key.FocusCmd{Tag: &findEditor})
				w.Invalidate() // next frame: the widget sees the FocusEvent
			}
			findBarFocused = focusedID == "find_bar"
			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
						case key.FocusEvent:
							// Focus gain/loss on the key queue (emitted when key.FocusCmd is
							// issued, i.e. on focus transitions). Nothing to do: the logic
							// layer already owns focus state.
						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
			}
			if sendFind {
				logic.FindQueryChan() <- newFind
			}
			// Skip layout feedback for frames built before the window size
			// was known (frame.ViewportDegenerate, set at frame-build time —
			// feedback delivery lags shaping by a frame, so checking the
			// current size here would miss them): a zero-width shape wraps
			// every line into many visual lines, and feeding those counts
			// back would poison the WrapIndex for the window's lines
			// (applied once, corrected only if those lines are re-shaped at a
			// real width — a restored scroll that moves the viewport away
			// never re-shapes them, and the poisoned counts then map a
			// legitimate scroll offset to the wrong line).
			if !frame.ViewportDegenerate {
				logic.LayoutChan() <- ui.LayoutFeedback{
					GlyphLayout:     glyphLayout,
					WindowText:      frame.WindowText,
					WindowStartByte: frame.WindowStartByte,
					WindowStartLine: frame.WindowStartLine,
					EditSeq:         frame.EditSeq,
					ScrollOffset:    frame.ScrollOffset,
				}
			}
		default:
			handleEvent(e)
		}
	}
}

// exclEqual reports whether two exclusion-rect sets are identical.
// newSessionSaver builds the relaunch-session file writer registered with
// the logic goroutine (spec §7). The file is a tiny JSON snapshot; a torn
// write is rejected by loadSession's parse on the next launch, so a plain
// write is safe (no temp+rename needed).
func newSessionSaver(path string) func(editor.SessionState) {
	return func(s editor.SessionState) {
		b, err := json.Marshal(s)
		if err != nil {
			log.Printf("session: marshal: %v", err)
			return
		}
		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
			log.Printf("session: mkdir: %v", err)
			return
		}
		if err := os.WriteFile(path, b, 0o600); err != nil {
			log.Printf("session: write: %v", err)
		}
	}
}

// loadSession reads and sanity-checks the relaunch session file (spec §7).
// ok=false when there is no session, it is corrupt, or nothing is restorable
// — in which case the app starts in the browser as before.
func loadSession(path string) (editor.SessionState, bool) {
	b, err := os.ReadFile(path)
	if err != nil {
		return editor.SessionState{}, false
	}
	var s editor.SessionState
	s.ScrollLine = -1 // pre-line session files lack the key; 0 would restore to the top
	if err := json.Unmarshal(b, &s); err != nil {
		return editor.SessionState{}, false
	}
	// A partial/corrupt file must not restore garbage positions.
	if s.Cursor < 0 {
		s.Cursor = 0
	}
	if s.Scroll < 0 {
		s.Scroll = 0
	}
	if s.SelStart < -1 || s.SelEnd < -1 || s.SelEnd <= s.SelStart {
		s.SelStart, s.SelEnd = -1, -1
	}
	if s.FindCurByte < -1 {
		s.FindCurByte = -1
	}
	if s.ScrollLine < -1 {
		s.ScrollLine = -1
	}
	if s.ScrollSub < 0 {
		s.ScrollSub = 0
	}
	if s.File == "" {
		return editor.SessionState{}, false
	}
	return s, true
}

func exclEqual(a, b [][4]int) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}

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()
	}
}