// MCP server registration. codex's `mcp add` writes into the user's
// global config; we use a per-agent stable name so multiple Plexum
// agents using codex don't collide. Registration is idempotent and
// performed lazily before the first turn that needs it.

package runner

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
)

var registered sync.Map // agentID → bool (registration done this process)

// EnsureCodexMCPRegistered makes sure codex's user config has an MCP
// server entry for this agent named plexum-host-<sanitized>. Returns
// the entry's tool-name namespace prefix so the caller can build
// req.Tools wire shapes if needed.
//
// The socket path baked into the env is StableSocketPath(agentID) —
// the same value the per-turn bridge listens on.
func EnsureCodexMCPRegistered(ctx context.Context, codexBinary, pluginBinary, agentID string) (string, error) {
	name := codexServerName(agentID)
	if _, ok := registered.Load(name); ok {
		return name, nil
	}
	// Remove first so we don't get "already exists"; ignore error.
	_ = exec.CommandContext(ctx, codexBinary, "mcp", "remove", name).Run()

	args := []string{
		"mcp", "add",
		"--env", "PLEXUM_MCP_SOCKET=" + StableSocketPath(agentID),
		"--env", "PLEXUM_MCP_AGENT_ID=" + agentID,
		name, "--", pluginBinary, "mcp-host",
	}
	cmd := exec.CommandContext(ctx, codexBinary, args...)
	if out, err := cmd.CombinedOutput(); err != nil {
		return "", fmt.Errorf("codex mcp add: %w: %s", err, strings.TrimSpace(string(out)))
	}
	registered.Store(name, true)
	return name, nil
}

// StableSocketPath returns the per-agent unix socket path the bridge
// listens on AND codex's mcp-host subprocess dials into. Keeping it
// stable lets us register codex's MCP server once and reuse it.
func StableSocketPath(agentID string) string {
	return filepath.Join(os.TempDir(), "plexum-codex-mcp-"+sanitize(agentID)+".sock")
}

// codexServerName produces the per-agent MCP server name codex stores
// in its global config. Names need to be filesystem-safe; we just
// reuse the sanitised agent id.
func codexServerName(agentID string) string {
	return "plexum-host-" + sanitize(agentID)
}

func sanitize(s string) string {
	out := make([]byte, 0, len(s))
	for i := 0; i < len(s); i++ {
		c := s[i]
		switch {
		case c >= 'a' && c <= 'z', c >= 'A' && c <= 'Z',
			c >= '0' && c <= '9', c == '-', c == '_':
			out = append(out, c)
		default:
			out = append(out, '_')
		}
	}
	return string(out)
}