// Package registry provides the global capability registry. Every capability a
// character can use — tools, skills, channels, MCP servers and IoT providers —
// is registered here so it is globally shared and always available to any
// character and mode (DevDocs/design/01-角色人格与行为模式.md §4).
//
// It is the single source of truth that tool dispatch (M2) and plugin/skill/MCP
// wiring (M5) read from. The registry is safe for concurrent use; it implements
// the pkg/plugins/sdk Registrar interface so plugins register through the SDK
// helpers without knowing this concrete type.
package registry

import (
	"errors"
	"fmt"
	"sync"

	"git.yeij.top/AskaEth/Cyrene_v2/pkg/plugins/sdk"
)

// Kind classifies a registered capability.
type Kind string

const (
	// KindTool is a callable function with a JSON Schema (sdk.Tool).
	KindTool Kind = "tool"
	// KindSkill is a reusable workflow with steps, prompts, refs and guardrails
	// (sdk.Skill).
	KindSkill Kind = "skill"
	// KindChannel is a platform adapter (sdk.Channel).
	KindChannel Kind = "channel"
	// KindMCP is a capability exposed by an MCP server (subsystem-owned).
	KindMCP Kind = "mcp"
	// KindIoT is an IoT device or provider capability (subsystem-owned).
	KindIoT Kind = "iot"
)

// Capability is a globally shared, always-available capability registered in
// the registry.
type Capability struct {
	// Name is the unique capability identifier.
	Name string
	// Kind classifies the capability.
	Kind Kind
	// Description is a human-readable summary used for selection and display.
	Description string
	// Value is the underlying capability object. For KindTool/KindSkill/
	// KindChannel it is the SDK interface from pkg/plugins/sdk; for KindMCP and
	// KindIoT it is owned by the relevant subsystem.
	Value any
}

// Registry is the thread-safe global capability registry.
type Registry struct {
	mu   sync.RWMutex
	caps map[string]Capability
}

// Compile-time assertion that *Registry satisfies the SDK Registrar interface.
var _ sdk.Registrar = (*Registry)(nil)

// Sentinel errors returned by the registry. Use errors.Is to test for them.
var (
	// ErrNotFound is returned by Get when no capability has the given name.
	ErrNotFound = errors.New("registry: capability not found")
	// ErrDuplicate is returned by Register when a capability with the same name
	// is already registered.
	ErrDuplicate = errors.New("registry: capability already registered")
	// ErrInvalidArgument is returned when a capability has an empty name, an
	// unknown kind, or a nil Value.
	ErrInvalidArgument = errors.New("registry: invalid capability")
)

// New returns an empty, concurrency-safe registry.
func New() *Registry {
	return &Registry{caps: make(map[string]Capability)}
}

// Register adds cap to the registry. It returns ErrInvalidArgument when the
// name is empty, the kind is unknown or the Value is nil, and ErrDuplicate when
// a capability with the same name already exists.
func (r *Registry) Register(cap Capability) error {
	if cap.Name == "" || !validKind(cap.Kind) || cap.Value == nil {
		return fmt.Errorf("registry: register %q: %w", cap.Name, ErrInvalidArgument)
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	if _, exists := r.caps[cap.Name]; exists {
		return fmt.Errorf("registry: register %q: %w", cap.Name, ErrDuplicate)
	}
	r.caps[cap.Name] = cap
	return nil
}

// Get returns the capability registered under name. It returns ErrNotFound when
// no such capability is registered.
func (r *Registry) Get(name string) (Capability, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()
	cap, ok := r.caps[name]
	if !ok {
		return Capability{}, fmt.Errorf("registry: get %q: %w", name, ErrNotFound)
	}
	return cap, nil
}

// List returns a copy of the capabilities whose Kind matches kind. An empty
// kind returns every registered capability. The returned slice is owned by the
// caller and safe to mutate.
func (r *Registry) List(kind Kind) []Capability {
	r.mu.RLock()
	defer r.mu.RUnlock()
	out := make([]Capability, 0, len(r.caps))
	for _, cap := range r.caps {
		if kind != "" && cap.Kind != kind {
			continue
		}
		out = append(out, cap)
	}
	return out
}

// RegisterTool registers t as a KindTool capability.
func (r *Registry) RegisterTool(t sdk.Tool) error {
	if t == nil {
		return fmt.Errorf("registry: register tool: %w", ErrInvalidArgument)
	}
	return r.Register(Capability{
		Name:        t.Name(),
		Kind:        KindTool,
		Description: t.Description(),
		Value:       t,
	})
}

// RegisterSkill registers s as a KindSkill capability.
func (r *Registry) RegisterSkill(s sdk.Skill) error {
	if s == nil {
		return fmt.Errorf("registry: register skill: %w", ErrInvalidArgument)
	}
	return r.Register(Capability{
		Name:        s.Name(),
		Kind:        KindSkill,
		Description: s.Description(),
		Value:       s,
	})
}

// RegisterChannel registers c as a KindChannel capability.
func (r *Registry) RegisterChannel(c sdk.Channel) error {
	if c == nil {
		return fmt.Errorf("registry: register channel: %w", ErrInvalidArgument)
	}
	return r.Register(Capability{
		Name:        c.Name(),
		Kind:        KindChannel,
		Description: c.Name(),
		Value:       c,
	})
}

// validKind reports whether k is one of the known capability kinds.
func validKind(k Kind) bool {
	switch k {
	case KindTool, KindSkill, KindChannel, KindMCP, KindIoT:
		return true
	default:
		return false
	}
}