package model

import (
	"errors"
	"fmt"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
)

// Provider names accepted by the provider-aware factory. These are the only two
// protocols the factory understands today; adding a vendor means adding a case
// here plus a matching adapter, not touching the rest of the package.
const (
	// ProviderOpenAI selects the OpenAI-compatible /chat/completions protocol.
	ProviderOpenAI = "openai"
	// ProviderAnthropic selects the Anthropic Messages /v1/messages protocol.
	ProviderAnthropic = "anthropic"
)

// ErrUnknownProvider is returned by the provider-aware factory when the
// configured provider name is not recognized.
var ErrUnknownProvider = errors.New("model: unknown provider")

// NewChatAdapter builds a single provider adapter selected by cfg.Provider. The
// empty provider defaults to openai for backward compatibility. An unrecognized
// provider returns ErrUnknownProvider.
func NewChatAdapter(cfg config.LLMConfig) (Adapter, error) {
	switch cfg.Provider {
	case ProviderOpenAI, "":
		return NewOpenAIChat(cfg), nil
	case ProviderAnthropic:
		return NewAnthropicChat(cfg), nil
	default:
		return nil, fmt.Errorf("model: %w: provider %q", ErrUnknownProvider, cfg.Provider)
	}
}

// NewChatChain builds a fallback Chain for the configured provider: the primary
// model first, then the provider's fallback model when set and distinct. Each
// step is served by an adapter of the selected protocol. The empty provider
// defaults to openai. An unrecognized provider returns ErrUnknownProvider.
func NewChatChain(cfg config.LLMConfig) (*Chain, error) {
	switch cfg.Provider {
	case ProviderOpenAI, "":
		return newOpenAIChain(cfg)
	case ProviderAnthropic:
		return newAnthropicChain(cfg)
	default:
		return nil, fmt.Errorf("model: %w: provider %q", ErrUnknownProvider, cfg.Provider)
	}
}

// newOpenAIChain builds a fallback chain from the OpenAI-compatible config block.
// Each step is an OpenAIChatAdapter against the configured endpoint.
func newOpenAIChain(cfg config.LLMConfig, opts ...OpenAIOption) (*Chain, error) {
	if cfg.BaseURL == "" || cfg.Model == "" {
		return nil, ErrNoModel
	}
	steps := []Step{{Model: cfg.Model, Adapter: NewOpenAIChat(cfg, opts...)}}
	if cfg.Fallback != "" && cfg.Fallback != cfg.Model {
		steps = append(steps, Step{Model: cfg.Fallback, Adapter: NewOpenAIChat(cfg, opts...)})
	}
	return NewChain(steps...), nil
}

// newAnthropicChain builds a fallback chain from the Anthropic config block. Each
// step is an AnthropicChatAdapter against the configured /v1/messages endpoint.
func newAnthropicChain(cfg config.LLMConfig) (*Chain, error) {
	if cfg.AnthropicBaseURL == "" || cfg.AnthropicModel == "" {
		return nil, ErrNoModel
	}
	steps := []Step{{Model: cfg.AnthropicModel, Adapter: NewAnthropicChat(cfg)}}
	if cfg.AnthropicFallback != "" && cfg.AnthropicFallback != cfg.AnthropicModel {
		steps = append(steps, Step{Model: cfg.AnthropicFallback, Adapter: NewAnthropicChat(cfg)})
	}
	return NewChain(steps...), nil
}

// DefaultModelForProvider returns the primary model name for the configured
// provider: the flat OpenAI Model for "openai", the Anthropic model for
// "anthropic". Used by callers (e.g. cmd/cyrene) to seed a Router's default.
func DefaultModelForProvider(cfg config.LLMConfig) string {
	if cfg.Provider == ProviderAnthropic {
		return cfg.AnthropicModel
	}
	return cfg.Model
}