package app

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/hjbdev/patterm/internal/persist"
	"github.com/hjbdev/patterm/internal/preset"
)

// Launcher knows how to turn a preset into a running child. Both the
// palette and the MCP spawn_agent tool route through here so MCP
// injection happens consistently. SPEC §10.
type Launcher struct {
	sess       *Session
	mcpSocket  string
	bin        string // path to this binary (for the mcp-stdio subcommand)
	sizeMu     sync.Mutex
	cols, rows uint16
}

func NewLauncher(sess *Session, mcpSocket string, cols, rows uint16) *Launcher {
	bin, err := os.Executable()
	if err != nil {
		bin = "patterm"
	}
	return &Launcher{sess: sess, mcpSocket: mcpSocket, bin: bin, cols: cols, rows: rows}
}

func (l *Launcher) SetSize(cols, rows uint16) {
	l.sizeMu.Lock()
	defer l.sizeMu.Unlock()
	l.cols, l.rows = cols, rows
}

func (l *Launcher) size() (uint16, uint16) {
	l.sizeMu.Lock()
	defer l.sizeMu.Unlock()
	return l.cols, l.rows
}

// LaunchAgent spawns the agent preset, applies the preset's MCP
// injection, waits for the ready signal, and types initial_prompt into
// the PTY. SPEC §7 spawn_agent, §8 conversation protocol.
func (l *Launcher) LaunchAgent(p *preset.Preset, displayName, initialPrompt, parentID string) (*Child, error) {
	if p.Kind != preset.KindAgent {
		return nil, fmt.Errorf("launch: %q is not an agent preset", p.Name)
	}
	argv := append([]string(nil), p.Argv...)
	env := l.sess.ChildEnv()
	for k, v := range p.Env {
		env = append(env, k+"="+v)
	}

	identity := mintIdentity()
	var cleanupPaths []string
	cleanup := func() {
		for _, path := range cleanupPaths {
			_ = os.RemoveAll(path)
		}
	}

	if p.MCPInjection != nil {
		switch p.MCPInjection.Kind {
		case "flag":
			if p.MCPInjection.Flag == "" {
				return nil, fmt.Errorf("preset %s: mcp_injection.flag required for kind=flag", p.Name)
			}
			mcpConfigPath, err := l.writeMCPConfig(identity)
			if err != nil {
				return nil, err
			}
			cleanupPaths = append(cleanupPaths, mcpConfigPath)
			argv = append(argv, p.MCPInjection.Flag, mcpConfigPath)
		case "env_var":
			if p.MCPInjection.Var == "" {
				return nil, fmt.Errorf("preset %s: mcp_injection.var required for kind=env_var", p.Name)
			}
			mcpConfigPath, err := l.writeMCPConfig(identity)
			if err != nil {
				return nil, err
			}
			cleanupPaths = append(cleanupPaths, mcpConfigPath)
			env = append(env, p.MCPInjection.Var+"="+mcpConfigPath)
		case "config_file":
			// Merge patterm's MCP entry into a vendored copy of the
			// user's existing config file, then point the child at the
			// vendored copy via the preset's home_var. The real config
			// file is never modified.
			envAssign, homeDir, mErr := mcpConfigMerge(p, p.MCPInjection, identity, l.bin, l.mcpSocket)
			if mErr != nil {
				return nil, mErr
			}
			cleanupPaths = append(cleanupPaths, homeDir)
			env = append(env, envAssign)
		case "cli_override":
			// Inline -c key=value overrides for agents that accept
			// them (codex's `-c mcp_servers.patterm.command=...`). No
			// filesystem footprint, so the user's real config and auth
			// are untouched.
			extra, err := mcpCLIOverrideArgs(p, p.MCPInjection, identity, l.bin, l.mcpSocket)
			if err != nil {
				return nil, err
			}
			argv = append(argv, extra...)
		case "config_env":
			// Read the user's config, merge patterm in, and pass the
			// merged document inline via an env var (opencode's
			// OPENCODE_CONFIG_CONTENT). Nothing is written to disk and
			// XDG_CONFIG_HOME stays as the user set it.
			assignment, err := mcpConfigEnv(p, p.MCPInjection, identity, l.bin, l.mcpSocket)
			if err != nil {
				return nil, err
			}
			env = append(env, assignment)
		default:
			cleanup()
			return nil, fmt.Errorf("preset %s: unknown mcp_injection.kind %q", p.Name, p.MCPInjection.Kind)
		}
	}

	// Spawn with the chosen identity.
	cols, rows := l.size()
	c, err := l.sess.Spawn(SpawnSpec{
		Kind:         KindAgent,
		Argv:         argv,
		Env:          env,
		Name:         displayName,
		ParentID:     parentID,
		PresetRef:    p.Name,
		Identity:     identity,
		CleanupPaths: cleanupPaths,
	}, cols, rows)
	if err != nil {
		cleanup()
		return nil, err
	}

	// Wait for the preset's ready signal, then type the initial prompt.
	idle := time.Duration(1000) * time.Millisecond
	if p.ReadySignal != nil && p.ReadySignal.IdleMS > 0 {
		idle = time.Duration(p.ReadySignal.IdleMS) * time.Millisecond
	}
	go func() {
		waitForIdle(c, idle, 30*time.Second)
		if initialPrompt == "" {
			return
		}
		// InjectAsOrchestrator splits Enter onto its own PTY write so
		// claude / codex / opencode treat the CR as a key event
		// rather than the tail end of a multi-byte paste.
		_ = c.InjectAsOrchestrator([]byte(initialPrompt + "\r"))
	}()
	return c, nil
}

// LaunchCommandPreset spawns a process preset as a SPEC §7 command
// entry. No MCP injection; just argv. The entry is session-persistent
// (survives PTY exit so it can be Restart'd).
func (l *Launcher) LaunchCommandPreset(p *preset.Preset, displayName, parentID string) (*Child, error) {
	if p.Kind != preset.KindCommand {
		return nil, fmt.Errorf("launch: %q is not a command preset", p.Name)
	}
	env := l.sess.ChildEnv()
	for k, v := range p.Env {
		env = append(env, k+"="+v)
	}
	cols, rows := l.size()
	return l.sess.Spawn(SpawnSpec{
		Kind:      KindCommand,
		Argv:      p.ResolvedArgv(),
		Env:       env,
		Name:      displayName,
		ParentID:  parentID,
		WorkDir:   p.WorkingDir,
		PresetRef: p.Name,
	}, cols, rows)
}

// LaunchCommandArgv spawns a freeform-argv command entry. Trust gating
// (SPEC §7) lives one level up in toolHost — by the time we get here
// trust is settled (freeform argv is implicitly trusted).
func (l *Launcher) LaunchCommandArgv(argv []string, displayName, parentID, workDir string, env []string, shell bool) (*Child, error) {
	if shell && len(argv) > 0 {
		argv = []string{"sh", "-lc", strings.Join(argv, " ")}
	}
	if env == nil {
		env = l.sess.ChildEnv()
	}
	cols, rows := l.size()
	return l.sess.Spawn(SpawnSpec{
		Kind:     KindCommand,
		Argv:     argv,
		Env:      env,
		Name:     displayName,
		ParentID: parentID,
		WorkDir:  workDir,
	}, cols, rows)
}

// RestoreCommand re-spawns a persisted top-level command entry. If
// the entry has a PresetRef and the preset still exists, the spawn
// goes through LaunchCommandPreset (so preset.Env / WorkingDir stay
// authoritative). Otherwise the saved argv runs directly via
// LaunchCommandArgv with shell=false — entries that were originally
// `shell: true` were already wrapped into `["sh","-lc",...]` before
// persistence, so re-wrapping isn't needed.
//
// Returns the freshly minted Child. The caller is responsible for
// setting auto-restart back on the returned entry.
func (l *Launcher) RestoreCommand(e persist.Entry, presets preset.Set) (*Child, error) {
	if e.PresetRef != "" {
		for _, p := range presets.Processes {
			if p.Name == e.PresetRef {
				return l.LaunchCommandPreset(p, e.Name, "")
			}
		}
		// Preset has been deleted since the entry was saved. Fall
		// through to argv-based restore using whatever the saved
		// command looked like at the time.
	}
	if len(e.Argv) == 0 {
		return nil, fmt.Errorf("restore: entry %s has no argv", e.ID)
	}
	return l.LaunchCommandArgv(e.Argv, e.Name, "", e.WorkDir, nil, false)
}

// LaunchTerminal spawns a bare interactive shell. SPEC §7 kind=terminal.
// argv defaults to $SHELL -i when empty.
func (l *Launcher) LaunchTerminal(argv []string, displayName, parentID, workDir string, env []string) (*Child, error) {
	if len(argv) == 0 {
		sh := os.Getenv("SHELL")
		if sh == "" {
			sh = "/bin/sh"
		}
		argv = []string{sh, "-i"}
	}
	if env == nil {
		env = l.sess.ChildEnv()
	}
	cols, rows := l.size()
	return l.sess.Spawn(SpawnSpec{
		Kind:     KindTerminal,
		Argv:     argv,
		Env:      env,
		Name:     displayName,
		ParentID: parentID,
		WorkDir:  workDir,
	}, cols, rows)
}

func (l *Launcher) writeMCPConfig(identity string) (string, error) {
	dir, err := preset.ConfigDir()
	if err != nil {
		return "", err
	}
	dir = filepath.Join(dir, "mcp")
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return "", err
	}
	path := filepath.Join(dir, identity+".json")
	cfg := map[string]any{
		"mcpServers": map[string]any{
			"patterm": map[string]any{
				"command": l.bin,
				"args":    []string{"mcp-stdio", "--socket", l.mcpSocket, "--identity", identity},
			},
		},
	}
	body, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return "", err
	}
	body = append(body, '\n')
	if err := os.WriteFile(path, body, 0o600); err != nil {
		return "", err
	}
	return path, nil
}

// waitForIdle polls the child's IdleMS until it exceeds idle, or until
// max elapses.
func waitForIdle(c *Child, idle, max time.Duration) {
	deadline := time.Now().Add(max)
	tick := time.NewTicker(100 * time.Millisecond)
	defer tick.Stop()
	for {
		<-tick.C
		if c.Status() != StatusRunning {
			return
		}
		if c.IdleMS() >= idle.Milliseconds() && c.lastWriteNS.Load() != 0 {
			return
		}
		if time.Now().After(deadline) {
			return
		}
	}
}

// joinArgs flattens an argv slice into a single line (used for display
// hints).
func joinArgs(argv []string) string { return strings.Join(argv, " ") }