package main

import (
	"context"
	"log/slog"
	"os"
	"strconv"
	"strings"

	"reasonix/internal/config"
	"reasonix/internal/plugin"
	"reasonix/internal/proc"
)

// bumpExtensionGeneration records that plugin/MCP configuration changed while
// controller builds may still be running off the lifecycle lock. In-flight
// builds that finish with a stale generation must not publish.
func (a *App) bumpExtensionGeneration() {
	if a == nil {
		return
	}
	a.extensionGeneration.Add(1)
}

func (a *App) currentExtensionGeneration() uint64 {
	if a == nil {
		return 0
	}
	return a.extensionGeneration.Load()
}

// lockMCPMutation serializes shared-Host boot with live MCP mutations without
// holding runtimeAdmissionMu while an optimistic controller build finishes its
// extension startup. A final generation bump invalidates builds that loaded
// configuration while the mutation held the gate.
func (a *App) lockMCPMutation(operation string) func() {
	if hook := a.runtimeMutationBeforeLockHook; hook != nil {
		hook(operation)
	}
	a.runtimeRebuildMu.Lock()
	a.extensionBuildMu.Lock()
	a.runtimeAdmissionMu.Lock()
	return func() {
		a.bumpExtensionGeneration()
		a.runtimeAdmissionMu.Unlock()
		a.extensionBuildMu.Unlock()
		a.runtimeRebuildMu.Unlock()
	}
}

type sharedHostMCPRegistration struct {
	scope     *plugin.RegistrationScope
	finished  bool
	committed bool
}

// beginSharedHostMCPRegistration attributes only context-scoped connections to
// this build. Unrelated Host writes never become rollback candidates.
func beginSharedHostMCPRegistration(ctx context.Context, host *plugin.Host) (context.Context, *sharedHostMCPRegistration) {
	registration := &sharedHostMCPRegistration{}
	if host == nil {
		return ctx, registration
	}
	registration.scope = host.BeginRegistrationScope()
	return plugin.ContextWithRegistrationScope(ctx, registration.scope), registration
}

func (r *sharedHostMCPRegistration) rollback() {
	if r == nil || r.finished {
		return
	}
	r.finished = true
	if r.scope != nil {
		r.scope.AbortAndRollback()
	}
}

func (r *sharedHostMCPRegistration) commit() bool {
	if r == nil {
		return true
	}
	if r.finished {
		return r.committed
	}
	if r.scope != nil && !r.scope.Commit() {
		r.finished = true
		return false
	}
	r.finished = true
	r.committed = true
	return true
}

func (a *App) saveDesktopMCPServerAndBump(root string, entry config.PluginEntry) error {
	if err := a.saveDesktopMCPServer(root, entry); err != nil {
		return err
	}
	a.bumpExtensionGeneration()
	return nil
}

// sharedPluginHost is a reference-counted plugin.Host shared across tabs
// that share the same workspace root. Multiple controllers (one per tab)
// use the same Host so MCP subprocesses (CodeGraph, etc.) are spawned once.
type sharedPluginHost struct {
	host *plugin.Host
	refs int
}

// acquireSharedHost returns a shared *plugin.Host for the given workspace root.
// The first call creates the host; subsequent calls increment a refcount and
// return the same host. The caller must call releaseSharedHost when the tab
// no longer needs the host.
func (a *App) acquireSharedHost(root string) *plugin.Host {
	a.sharedHostsMu.Lock()
	defer a.sharedHostsMu.Unlock()

	if a.sharedHosts == nil {
		a.sharedHosts = make(map[string]*sharedPluginHost)
	}

	entry, ok := a.sharedHosts[root]
	if ok {
		entry.refs++
		slog.Debug("shared host acquired (reused)", "root", root, "refs", entry.refs)
		return entry.host
	}

	// Full Apps surface; a failed sandbox listener degrades here to
	// interactive-v1 rather than downgrading a negotiated session.
	host := plugin.NewHostWithProfile(plugin.HostProfileDesktopApps)
	if !a.mcpAppsSandboxAvailable() {
		host = plugin.NewHostWithProfile(plugin.HostProfileInteractive)
	}
	a.sharedHosts[root] = &sharedPluginHost{host: host, refs: 1}
	slog.Debug("shared host acquired (new)", "root", root)
	return host
}

// lookupSharedHost returns an existing shared host for the given root, or nil.
// Unlike acquireSharedHost, it does NOT increment the refcount — use this when
// rebuilding a controller for an existing tab that already holds a reference.
func (a *App) lookupSharedHost(root string) *plugin.Host {
	a.sharedHostsMu.Lock()
	defer a.sharedHostsMu.Unlock()
	if a.sharedHosts == nil {
		return nil
	}
	entry, ok := a.sharedHosts[root]
	if !ok {
		return nil
	}
	return entry.host
}

// reapOrphanCodeGraph kills any codegraph MCP subprocess that is not a
// direct child of the current Reasonix process. This cleans up orphaned
// processes from a previous crash or from older versions that leaked them,
// preventing accumulation across restarts.
func (a *App) reapOrphanCodeGraph() {
	myPID := os.Getpid()

	// Collect the PIDs of our direct children (the ones we own).
	// pgrep -P exits non-zero when there are no children; treat that as an
	// empty set and continue scanning for orphans rather than skipping the
	// entire reaping step.
	ours := map[int]bool{}
	out, err := proc.Command("pgrep", "-P", strconv.Itoa(myPID)).Output()
	if err == nil {
		for f := range strings.FieldsSeq(string(out)) {
			if pid, err := strconv.Atoi(f); err == nil {
				ours[pid] = true
			}
		}
	}

	// Find every codegraph MCP process.
	out, err = proc.Command("pgrep", "-f", "codegraph\\.js serve --mcp").Output()
	if err != nil {
		return
	}
	for f := range strings.FieldsSeq(string(out)) {
		pid, err := strconv.Atoi(f)
		if err != nil || pid == myPID || ours[pid] {
			continue
		}
		// Verify the process is truly orphaned before killing it:
		// check its parent PID — if the parent is alive and isn't ours,
		// this codegraph belongs to another active Reasonix session.
		ppidOut, err := proc.Command("ps", "-o", "ppid=", "-p", strconv.Itoa(pid)).Output()
		if err != nil {
			continue
		}
		ppid, err := strconv.Atoi(strings.TrimSpace(string(ppidOut)))
		if err != nil || ppid == 0 {
			continue
		}
		// ppid==1 means the parent died and init reparented it — truly orphaned.
		if ppid != 1 {
			continue
		}
		if p, err := os.FindProcess(pid); err == nil {
			_ = p.Kill()
			slog.Debug("reaped orphan codegraph", "pid", pid)
		}
	}
}

// releaseSharedHost decrements the refcount for the workspace root and closes
// the shared host when no tabs reference it any more. Safe to call even when
// no acquire was made (no-op).
func (a *App) releaseSharedHost(root string) {
	a.sharedHostsMu.Lock()
	defer a.sharedHostsMu.Unlock()

	entry, ok := a.sharedHosts[root]
	if !ok {
		return
	}
	entry.refs--
	if entry.refs > 0 {
		slog.Debug("shared host released (still in use)", "root", root, "refs", entry.refs)
		return
	}

	delete(a.sharedHosts, root)
	entry.host.Close()
	slog.Debug("shared host closed", "root", root)
}

func (a *App) releaseTabSharedHost(tab *WorkspaceTab) {
	if tab == nil {
		return
	}
	// SharedHostKey is a.mu-guarded (the build goroutine publishes it under
	// the lock); do the take under the lock and the slow host release after.
	// Callers must not hold a.mu.
	a.mu.Lock()
	key := takeTabSharedHostKey(tab)
	a.mu.Unlock()
	if key == "" {
		return
	}
	a.releaseSharedHost(key)
}

// takeTabSharedHostKey clears the tab's shared-host key and returns it so the
// caller can release it later. Use from inside a.mu critical sections:
// releaseSharedHost may close the host and reap MCP subprocesses, which is far
// too slow to run under the app lock — call a.releaseSharedHost(key) after
// unlocking.
func takeTabSharedHostKey(tab *WorkspaceTab) string {
	if tab == nil || tab.SharedHostKey == "" {
		return ""
	}
	key := tab.SharedHostKey
	tab.SharedHostKey = ""
	return key
}

// closeAllSharedHosts closes every shared host. Called during app shutdown.
func (a *App) closeAllSharedHosts() {
	a.sharedHostsMu.Lock()
	defer a.sharedHostsMu.Unlock()

	for root, entry := range a.sharedHosts {
		delete(a.sharedHosts, root)
		entry.host.Close()
		slog.Debug("shared host closed (shutdown)", "root", root)
	}
}