// Package registry implements the character library and persona registration
// for the persona system. A character comes from the character library, binds
// exactly one persona, and declares the behavior modes it is good at; the
// registered persona additionally owns a per-persona memory isolation namespace
// and the emotion/affection state that follows the persona.
package registry

import (
	"fmt"
	"sync"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/persona/emotion"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/persona/loader"
)

// Character is an entity from the character library. It binds one persona and
// declares the behavior modes it excels at (as a suggestion, never an ability
// bound — see DevDocs/design/01).
type Character struct {
	// ID is the unique character identifier.
	ID string
	// Name is the display name of the character.
	Name string
	// Default marks this character as the library's default role.
	Default bool
	// PersonaID is the persona bound to this character.
	PersonaID string
	// Modes lists the behavior modes the character is good at.
	Modes []string
}

// Registry is the in-memory, concurrency-safe character library and persona
// registry. It also owns the emotion Manager so that emotion/affection always
// follow the registered persona.
type Registry struct {
	mu         sync.RWMutex
	personas   map[string]*loader.Persona
	characters map[string]*Character
	defaultID  string
	emotions   *emotion.Manager
}

// New returns an empty Registry.
func New() *Registry {
	return &Registry{
		personas:   make(map[string]*loader.Persona),
		characters: make(map[string]*Character),
		emotions:   emotion.NewManager(),
	}
}

// RegisterPersona registers p and builds its emotion machine and affection
// tracker. It fails when p is nil, has no id, is already registered, or its
// emotion/affection config is invalid.
func (r *Registry) RegisterPersona(p *loader.Persona) error {
	if p == nil {
		return fmt.Errorf("registry: nil persona")
	}
	if p.ID == "" {
		return fmt.Errorf("registry: persona id required")
	}
	machine, err := p.NewMachine()
	if err != nil {
		return fmt.Errorf("registry: persona %q machine: %w", p.ID, err)
	}
	affection, err := p.NewAffection()
	if err != nil {
		return fmt.Errorf("registry: persona %q affection: %w", p.ID, err)
	}

	r.mu.Lock()
	if _, ok := r.personas[p.ID]; ok {
		r.mu.Unlock()
		return fmt.Errorf("registry: persona %q already registered", p.ID)
	}
	r.personas[p.ID] = p
	r.mu.Unlock()

	r.emotions.Set(p.ID, machine, affection)
	return nil
}

// Persona returns the persona registered under id.
func (r *Registry) Persona(id string) (*loader.Persona, bool) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	p, ok := r.personas[id]
	return p, ok
}

// RegisterCharacter registers c. It requires c's persona to exist, so persona
// registration must happen first. A character marked Default becomes the
// library's default role.
func (r *Registry) RegisterCharacter(c *Character) error {
	if c == nil {
		return fmt.Errorf("registry: nil character")
	}
	if c.ID == "" {
		return fmt.Errorf("registry: character id required")
	}
	if c.Name == "" {
		return fmt.Errorf("registry: character %q name required", c.ID)
	}
	if c.PersonaID == "" {
		return fmt.Errorf("registry: character %q personaID required", c.ID)
	}

	r.mu.Lock()
	defer r.mu.Unlock()
	if _, ok := r.characters[c.ID]; ok {
		return fmt.Errorf("registry: character %q already registered", c.ID)
	}
	if _, ok := r.personas[c.PersonaID]; !ok {
		return fmt.Errorf("registry: character %q references unknown persona %q", c.ID, c.PersonaID)
	}
	r.characters[c.ID] = c
	if c.Default {
		r.defaultID = c.ID
	}
	return nil
}

// Character returns the character registered under id.
func (r *Registry) Character(id string) (*Character, bool) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	c, ok := r.characters[id]
	return c, ok
}

// SetDefaultCharacter makes the character with id the library default. It fails
// when id is not a registered character.
func (r *Registry) SetDefaultCharacter(id string) error {
	r.mu.Lock()
	defer r.mu.Unlock()
	c, ok := r.characters[id]
	if !ok {
		return fmt.Errorf("registry: set default to unknown character %q", id)
	}
	c.Default = true
	r.defaultID = id
	return nil
}

// DefaultCharacter returns the library's default character, if one is set.
func (r *Registry) DefaultCharacter() (*Character, bool) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	if r.defaultID == "" {
		return nil, false
	}
	c, ok := r.characters[r.defaultID]
	return c, ok
}

// MemoryNamespace returns the per-persona memory isolation namespace for the
// persona under personaID, guarding memory isolation between personas.
func (r *Registry) MemoryNamespace(personaID string) (string, bool) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	p, ok := r.personas[personaID]
	if !ok {
		return "", false
	}
	return p.MemoryNamespace(), true
}

// Emotions returns the emotion Manager that owns every registered persona's
// emotion and affection state.
func (r *Registry) Emotions() *emotion.Manager {
	return r.emotions
}

// CountPersonas returns the number of registered personas.
func (r *Registry) CountPersonas() int {
	r.mu.RLock()
	defer r.mu.RUnlock()
	return len(r.personas)
}

// CountCharacters returns the number of registered characters.
func (r *Registry) CountCharacters() int {
	r.mu.RLock()
	defer r.mu.RUnlock()
	return len(r.characters)
}