147 lines
3.6 KiB
Go
147 lines
3.6 KiB
Go
//go:build js && wasm
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package main
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import (
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"sync"
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mosh "github.com/unixshells/mosh-go"
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vt "github.com/unixshells/vt-go"
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)
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// stateTracker implements Dart-style received state management.
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// Each incoming diff is applied to a copy of the base state (looked up
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// by oldNum), producing a new state stored by newNum. The display
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// always shows the latest received state, diffed against what's
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// currently on screen. This eliminates garbled output from missed
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// diffs and overlapping state transitions.
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type stateTracker struct {
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mu sync.Mutex
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shadow *vt.Emulator
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shadowState uint64
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cols, rows int
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// Received states: stateNum → framebuffer snapshot.
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states map[uint64]*mosh.Framebuffer
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latestState uint64
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displayedFB *mosh.Framebuffer
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// Output buffer: pre-diffed ANSI ready for the terminal.
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output []byte
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}
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func newStateTracker(cols, rows int) *stateTracker {
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return &stateTracker{
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shadow: vt.NewEmulator(cols, rows),
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cols: cols,
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rows: rows,
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states: make(map[uint64]*mosh.Framebuffer),
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}
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}
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// applyDiff processes an incoming server diff using state tracking.
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// throwawayNum is the server's indication of which states it no longer references.
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func (st *stateTracker) applyDiff(diff []byte, oldNum, newNum, throwawayNum uint64) {
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st.mu.Lock()
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defer st.mu.Unlock()
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// Already have this state — skip.
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if _, ok := st.states[newNum]; ok {
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return
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}
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// Snapshot current shadow as oldNum if we don't have it.
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if oldNum == st.shadowState {
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if _, ok := st.states[oldNum]; !ok {
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st.states[oldNum] = mosh.SnapshotEmulator(st.shadow, true)
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}
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}
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// Need the base state to apply the diff.
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base, ok := st.states[oldNum]
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if !ok {
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// Unknown base state. Reset the shadow emulator and start fresh.
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st.resetShadow()
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st.shadowState = oldNum
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base = mosh.SnapshotEmulator(st.shadow, true)
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st.states[oldNum] = base
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} else if st.shadowState != oldNum {
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// Restore shadow to the base state.
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st.resetShadow()
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if base != nil {
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st.shadow.Write(base.Diff(nil))
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}
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}
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// Apply diff: feed hoststrings to shadow.
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instrs, err := mosh.UnmarshalHostMessage(diff)
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if err != nil {
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return
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}
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for _, hi := range instrs {
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if len(hi.Hoststring) > 0 {
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st.shadow.Write(hi.Hoststring)
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}
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}
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st.shadowState = newNum
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// Snapshot result.
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snap := mosh.SnapshotEmulator(st.shadow, true)
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st.states[newNum] = snap
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if newNum > st.latestState {
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st.latestState = newNum
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}
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// Prune states the server no longer references.
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if throwawayNum > 0 {
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for n := range st.states {
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if n < throwawayNum {
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delete(st.states, n)
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}
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}
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}
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// Display diff: compute ANSI difference between displayed and latest.
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latest := st.states[st.latestState]
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if latest != nil {
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ansi := latest.Diff(st.displayedFB)
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if len(ansi) > 0 {
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st.output = append(st.output, ansi...)
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}
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st.displayedFB = latest
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}
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}
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// poll returns accumulated ANSI output, or nil.
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func (st *stateTracker) poll() []byte {
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st.mu.Lock()
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defer st.mu.Unlock()
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if len(st.output) == 0 {
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return nil
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}
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out := st.output
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st.output = nil
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return out
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}
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// resize resets the state tracker for new dimensions.
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func (st *stateTracker) resize(cols, rows int) {
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st.mu.Lock()
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defer st.mu.Unlock()
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st.cols = cols
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st.rows = rows
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// Must create a new emulator for new dimensions.
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st.shadow = vt.NewEmulator(cols, rows)
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st.shadowState = 0
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st.states = make(map[uint64]*mosh.Framebuffer)
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st.displayedFB = nil
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}
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// resetShadow clears the shadow emulator without reallocating it.
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func (st *stateTracker) resetShadow() {
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st.shadow.Resize(st.cols, st.rows)
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st.shadow.Write([]byte("\033[H\033[2J\033[m"))
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}
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