package llm

import (
	"context"
	"fmt"
	"time"

	"github.com/cloudwego/eino/components/embedding"
	"github.com/cloudwego/eino/components/model"
	"github.com/cloudwego/eino/schema"
	einoopenai "github.com/cloudwego/eino-ext/components/model/openai"
	einoopenaiembedding "github.com/cloudwego/eino-ext/components/embedding/openai"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// EinoProvider implements the Provider interface by delegating to Eino's
// model.ChatModel + embedding.Embedder. This allows GoChat to use Eino's
// rich ecosystem of model implementations (OpenAI, Claude, Gemini, DeepSeek,
// Ark, Qwen, etc.) without changing any business logic code.
//
// The EinoProvider is constructed with:
//   - chatModel: a model.ToolCallingChatModel (or model.ChatModel) from eino-ext
//   - embedder: an embedding.Embedder from eino-ext
//
// If embedder is nil, CreateEmbedding returns an error. This happens when
// using providers like Anthropic that don't offer an embeddings API — in
// that case, configure a separate OpenAI-compatible embedding provider.
type EinoProvider struct {
	chatModel model.BaseChatModel
	embedder  Embedder
	// fallback embedder for providers that don't support embeddings (e.g. Anthropic)
	// if non-nil, used when embedder is nil
	fallbackEmbedder Embedder
}

// Embedder is the interface EinoProvider expects for embedding generation.
// This matches eino's embedding.Embedder interface exactly.
type Embedder = embedding.Embedder

// NewEinoProvider creates a new EinoProvider.
// chatModel must implement model.BaseChatModel (Generate + Stream).
// embedder is optional (can be nil if only chat completion is needed).
func NewEinoProvider(chatModel model.BaseChatModel, embedder Embedder) *EinoProvider {
	return &EinoProvider{
		chatModel: chatModel,
		embedder:  embedder,
	}
}

// SetFallbackEmbedder sets a fallback embedder used when the primary embedder
// is nil (e.g. when using Anthropic as chat model but OpenAI for embeddings).
func (p *EinoProvider) SetFallbackEmbedder(embedder Embedder) {
	p.fallbackEmbedder = embedder
}

// ChatCompletion sends a synchronous chat completion request via Eino.
func (p *EinoProvider) ChatCompletion(ctx context.Context, req ChatRequest) (*ChatResponse, error) {
	// Convert GoChat messages to Eino schema.Message
	messages := make([]*schema.Message, 0, len(req.Messages))
	for _, msg := range req.Messages {
		role := schema.RoleType(msg.Role)
		if role == "" {
			role = schema.User
		}
		messages = append(messages, &schema.Message{
			Role:    role,
			Content: msg.Content,
		})
		// Handle tool call fields
		if len(msg.ToolCalls) > 0 {
			messages[len(messages)-1].ToolCalls = convertToSchemaToolCalls(msg.ToolCalls)
		}
		if msg.ToolCallID != "" {
			messages[len(messages)-1].ToolCallID = msg.ToolCallID
			messages[len(messages)-1].ToolName = msg.Name
		}
	}

	// Build options
	opts := []model.Option{}
	if req.Temperature > 0 {
		opts = append(opts, WithTemperature(req.Temperature))
	}
	if req.MaxTokens > 0 {
		opts = append(opts, WithMaxTokens(req.MaxTokens))
	}

	// Call Eino model
	resp, err := p.chatModel.Generate(ctx, messages, opts...)
	if err != nil {
		applogger.L().Errorf("EinoProvider ChatCompletion: %v", err)
		return nil, fmt.Errorf("eino chat completion: %w", err)
	}

	// Convert Eino response to GoChat ChatResponse
	result := &ChatResponse{
		ID:      "",
		Object:  "chat.completion",
		Created: time.Now().Unix(),
		Model:   req.Model,
		Choices: []ChatChoice{},
	}

	if resp != nil {
		finishReason := ""
		if resp.ResponseMeta != nil {
			finishReason = resp.ResponseMeta.FinishReason
		}
		choice := ChatChoice{
			Index:        0,
			Message:      ChatMessage{Role: string(resp.Role), Content: resp.Content},
			FinishReason: finishReason,
		}
		// Convert tool calls if present
		if len(resp.ToolCalls) > 0 {
			choice.Message.ToolCalls = convertFromSchemaToolCalls(resp.ToolCalls)
		}
		result.Choices = append(result.Choices, choice)

		// Map usage metadata if available
		if resp.ResponseMeta != nil && resp.ResponseMeta.Usage != nil {
			result.Usage = TokenUsage{
				PromptTokens:     resp.ResponseMeta.Usage.PromptTokens,
				CompletionTokens: resp.ResponseMeta.Usage.CompletionTokens,
				TotalTokens:      resp.ResponseMeta.Usage.TotalTokens,
			}
		}
	}

	return result, nil
}

// ChatCompletionStream sends a streaming chat completion request via Eino.
// Chunks are delivered via the onChunk callback.
func (p *EinoProvider) ChatCompletionStream(ctx context.Context, req ChatRequest, onChunk func(StreamChunk) error) error {
	// Convert messages
	messages := make([]*schema.Message, 0, len(req.Messages))
	for _, msg := range req.Messages {
		role := schema.RoleType(msg.Role)
		if role == "" {
			role = schema.User
		}
		messages = append(messages, &schema.Message{
			Role:    role,
			Content: msg.Content,
		})
	}

	opts := []model.Option{}
	if req.Temperature > 0 {
		opts = append(opts, WithTemperature(req.Temperature))
	}
	if req.MaxTokens > 0 {
		opts = append(opts, WithMaxTokens(req.MaxTokens))
	}

	reader, err := p.chatModel.Stream(ctx, messages, opts...)
	if err != nil {
		return fmt.Errorf("eino stream: %w", err)
	}
	if reader == nil {
		return fmt.Errorf("eino stream returned nil reader")
	}
	defer reader.Close()

	for {
		chunk, err := reader.Recv()
		if err != nil {
			if err.Error() == "EOF" || err.Error() == "io: EOF" {
				break
			}
			return fmt.Errorf("eino stream recv: %w", err)
		}
		if chunk == nil {
			break
		}

		streamChunk := StreamChunk{
			Model: req.Model,
			Choices: []StreamChoice{
				{
					Index:        0,
					Delta:        StreamDelta{Content: chunk.Content},
				},
			},
		}
		if chunk.ResponseMeta != nil {
			streamChunk.Choices[0].FinishReason = chunk.ResponseMeta.FinishReason
		}

		if err := onChunk(streamChunk); err != nil {
			return fmt.Errorf("chunk callback: %w", err)
		}
	}

	return nil
}

// CreateEmbedding generates embeddings using the Eino embedder.
func (p *EinoProvider) CreateEmbedding(ctx context.Context, req EmbeddingRequest) (*EmbeddingResponse, error) {
	embedder := p.embedder
	if embedder == nil {
		embedder = p.fallbackEmbedder
	}
	if embedder == nil {
		return nil, fmt.Errorf("no embedder configured for this provider")
	}

	vectors, err := embedder.EmbedStrings(ctx, req.Input)
	if err != nil {
		return nil, fmt.Errorf("eino embedding: %w", err)
	}

	data := make([]EmbeddingData, 0, len(vectors))
	for i, vec := range vectors {
		data = append(data, EmbeddingData{
			Object:    "embedding",
			Index:     i,
			Embedding: vec,
		})
	}

	return &EmbeddingResponse{
		Object: "list",
		Data:   data,
		Model:  req.Model,
	}, nil
}

// --- Helper functions for tool call conversion ---

func convertToSchemaToolCalls(calls []ToolCall) []schema.ToolCall {
	result := make([]schema.ToolCall, 0, len(calls))
	for _, c := range calls {
		result = append(result, schema.ToolCall{
			ID:     c.ID,
			Type:   c.Type,
			Function: schema.FunctionCall{
				Name:      c.Function.Name,
				Arguments: c.Function.Arguments,
			},
		})
	}
	return result
}

func convertFromSchemaToolCalls(calls []schema.ToolCall) []ToolCall {
	result := make([]ToolCall, 0, len(calls))
	for _, c := range calls {
		result = append(result, ToolCall{
			ID:   c.ID,
			Type: c.Type,
			Function: ToolCallFunction{
				Name:      c.Function.Name,
				Arguments: c.Function.Arguments,
			},
		})
	}
	return result
}

// --- Model option helpers ---
// These wrap eino's model.Option to provide a simple API without importing
// eino's option package directly in business code.

// WithTemperature sets the temperature option for the model.
func WithTemperature(temp float64) model.Option {
	return model.WithTemperature(float32(temp))
}

// WithMaxTokens sets the max tokens option for the model.
func WithMaxTokens(maxTokens int) model.Option {
	return model.WithMaxTokens(maxTokens)
}

// NewProviderFromConfig creates the appropriate LLM provider based on provider name.
// Uses Eino (cloudwego/eino) as the underlying framework.
//
// For all provider types (openai/anthropic/azure/custom/empty), Eino's OpenAI
// ChatModel is used with the configured baseURL — this works for OpenAI-compatible
// APIs including domestic providers (Ark/Doubao/Qwen) by setting llm_base_url.
//
// Embeddings always use Eino's OpenAI Embedder (Anthropic has no embeddings API;
// OpenAI embeddings are the industry standard).
//
// If Eino initialization fails, falls back to the hand-written OpenAIProvider.
func NewProviderFromConfig(provider, apiKey, baseURL, modelName, embedModel string) Provider {
	ctx := context.Background()

	// Create Eino OpenAI ChatModel
	chatModelCfg := &einoopenai.ChatModelConfig{
		APIKey: apiKey,
		Model:  modelName,
	}
	if baseURL != "" {
		chatModelCfg.BaseURL = baseURL
	}

	chatModel, err := einoopenai.NewChatModel(ctx, chatModelCfg)
	if err != nil {
		applogger.L().Errorf("Eino: failed to create OpenAI chat model: %v, falling back to direct provider", err)
		return NewOpenAIProvider(OpenAIProviderConfig{
			APIKey:     apiKey,
			BaseURL:    baseURL,
			Model:      modelName,
			EmbedModel: embedModel,
		})
	}

	// Create Eino OpenAI Embedder
	var embedder Embedder
	if apiKey != "" {
		embedCfg := &einoopenaiembedding.EmbeddingConfig{
			APIKey: apiKey,
			Model:  embedModel,
		}
		if baseURL != "" {
			embedCfg.BaseURL = baseURL
		}
		if ed, err := einoopenaiembedding.NewEmbedder(ctx, embedCfg); err == nil {
			embedder = ed
		} else {
			applogger.L().Warnf("Eino: failed to create OpenAI embedder: %v, embeddings unavailable", err)
		}
	}

	applogger.L().Infof("Eino: provider initialized (model=%s, embed=%s, baseURL=%s)", modelName, embedModel, baseURL)
	return NewEinoProvider(chatModel, embedder)
}