// Package identity manages the per-agent Fabric API key registry at
// <profile>/fabric-identity.json. Format mirrors openclaw's
// fabric-identity.json so existing operator muscle memory transfers:
//
//	{
//	  "agents": {
//	    "<plexum-agent-id>": {
//	      "fabric_api_key": "fak_...",
//	      "fabric_user_id": "u_...",      // optional, recorded on register
//	      "fabric_email":   "...",        // optional
//	      "enabled":         true
//	    }
//	  }
//	}
//
// `plexum-fabric-register` writes here; the plugin reads from here at
// startup (and rereads on SIGHUP — future work).
package identity

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"sort"
	"sync"
)

// FileName is the basename under <profile>/.
const FileName = "fabric-identity.json"

// Entry is one agent's identity binding.
type Entry struct {
	FabricAPIKey string `json:"fabric_api_key"`
	FabricUserID string `json:"fabric_user_id,omitempty"`
	FabricEmail  string `json:"fabric_email,omitempty"`
	Enabled      bool   `json:"enabled"`
}

// Registry wraps the JSON file. Thread-safe.
type Registry struct {
	mu   sync.Mutex
	path string
	data map[string]*Entry
}

// Open loads (or creates an empty) registry at the given absolute path.
func Open(path string) (*Registry, error) {
	r := &Registry{path: path, data: map[string]*Entry{}}
	raw, err := os.ReadFile(path)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			return r, nil
		}
		return nil, fmt.Errorf("identity: read %s: %w", path, err)
	}
	if len(raw) == 0 {
		return r, nil
	}
	var wire struct {
		Agents map[string]*Entry `json:"agents"`
	}
	if err := json.Unmarshal(raw, &wire); err != nil {
		return nil, fmt.Errorf("identity: parse %s: %w", path, err)
	}
	if wire.Agents != nil {
		r.data = wire.Agents
	}
	return r, nil
}

// Lookup returns the entry for agentID (nil if missing).
func (r *Registry) Lookup(agentID string) *Entry {
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.data[agentID]
}

// Set inserts/replaces the entry for agentID. Does NOT persist.
func (r *Registry) Set(agentID string, e *Entry) {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.data[agentID] = e
}

// Delete removes agentID; returns true iff it was present.
func (r *Registry) Delete(agentID string) bool {
	r.mu.Lock()
	defer r.mu.Unlock()
	if _, ok := r.data[agentID]; !ok {
		return false
	}
	delete(r.data, agentID)
	return true
}

// AgentIDs returns the sorted list of registered agent ids.
func (r *Registry) AgentIDs() []string {
	r.mu.Lock()
	defer r.mu.Unlock()
	out := make([]string, 0, len(r.data))
	for k := range r.data {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}

// EnabledEntries returns a copy of (agentID, entry) for entries with
// Enabled=true. Plugin uses this to decide which agents to bring up.
func (r *Registry) EnabledEntries() map[string]*Entry {
	r.mu.Lock()
	defer r.mu.Unlock()
	out := map[string]*Entry{}
	for k, v := range r.data {
		if v != nil && v.Enabled {
			copyE := *v
			out[k] = &copyE
		}
	}
	return out
}

// Save atomically writes the registry (tmp+rename, 0600 — API keys live
// here, treat as secrets).
func (r *Registry) Save() error {
	r.mu.Lock()
	defer r.mu.Unlock()
	if err := os.MkdirAll(filepath.Dir(r.path), 0o755); err != nil {
		return fmt.Errorf("identity: mkdir: %w", err)
	}
	payload := struct {
		Agents map[string]*Entry `json:"agents"`
	}{Agents: r.data}
	data, err := json.MarshalIndent(payload, "", "  ")
	if err != nil {
		return err
	}
	tmp := r.path + ".tmp"
	if err := os.WriteFile(tmp, data, 0o600); err != nil {
		return fmt.Errorf("identity: write tmp: %w", err)
	}
	return os.Rename(tmp, r.path)
}

// DefaultPath returns the canonical path under PLEXUM_PROFILE_ROOT or
// ~/.plexum if the env var isn't set.
func DefaultPath() string {
	root := os.Getenv("PLEXUM_PROFILE_ROOT")
	if root == "" {
		home, _ := os.UserHomeDir()
		root = filepath.Join(home, ".plexum")
	}
	return filepath.Join(root, FileName)
}