package anthropic

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"

	"git.mlow.ca/mlow/lmcli/pkg/api"
)

const ANTHROPIC_VERSION = "2023-06-01"

type AnthropicClient struct {
	APIKey  string
	BaseURL string
}

type ChatCompletionMessage struct {
	Role    string      `json:"role"`
	Content interface{} `json:"content"`
}

type Tool struct {
	Name        string      `json:"name"`
	Description string      `json:"description"`
	InputSchema InputSchema `json:"input_schema"`
}

type InputSchema struct {
	Type       string              `json:"type"`
	Properties map[string]Property `json:"properties"`
	Required   []string            `json:"required"`
}

type Property struct {
	Type        string   `json:"type"`
	Description string   `json:"description"`
	Enum        []string `json:"enum,omitempty"`
}

type ChatCompletionRequest struct {
	Model       string                  `json:"model"`
	Messages    []ChatCompletionMessage `json:"messages"`
	System      string                  `json:"system,omitempty"`
	Tools       []Tool                  `json:"tools,omitempty"`
	MaxTokens   int                     `json:"max_tokens"`
	Temperature float32                 `json:"temperature,omitempty"`
	Stream      bool                    `json:"stream"`
}

type ContentBlock struct {
	Type                   string      `json:"type"`
	Text                   string      `json:"text,omitempty"`
	ID                     string      `json:"id,omitempty"`
	Name                   string      `json:"name,omitempty"`
	Input                  interface{} `json:"input,omitempty"`
	partialJsonAccumulator string
}

type ChatCompletionResponse struct {
	ID         string         `json:"id"`
	Type       string         `json:"type"`
	Role       string         `json:"role"`
	Model      string         `json:"model"`
	Content    []ContentBlock `json:"content"`
	StopReason string         `json:"stop_reason"`
	Usage      Usage          `json:"usage"`
}

type Usage struct {
	InputTokens  int `json:"input_tokens"`
	OutputTokens int `json:"output_tokens"`
}

type StreamEvent struct {
	Type    string      `json:"type"`
	Message interface{} `json:"message,omitempty"`
	Index   int         `json:"index,omitempty"`
	Delta   interface{} `json:"delta,omitempty"`
}

func convertTools(tools []api.ToolSpec) []Tool {
	anthropicTools := make([]Tool, len(tools))
	for i, tool := range tools {
		properties := make(map[string]Property)
		for _, param := range tool.Parameters {
			properties[param.Name] = Property{
				Type:        param.Type,
				Description: param.Description,
				Enum:        param.Enum,
			}
		}

		var required []string
		for _, param := range tool.Parameters {
			if param.Required {
				required = append(required, param.Name)
			}
		}

		anthropicTools[i] = Tool{
			Name:        tool.Name,
			Description: tool.Description,
			InputSchema: InputSchema{
				Type:       "object",
				Properties: properties,
				Required:   required,
			},
		}
	}
	return anthropicTools
}

func createChatCompletionRequest(
	params api.RequestParameters,
	messages []api.Message,
) (string, ChatCompletionRequest) {
	requestMessages := make([]ChatCompletionMessage, 0, len(messages))
	var systemMessage string

	for _, m := range messages {
		if m.Role == api.MessageRoleSystem {
			systemMessage = m.Content
			continue
		}

		var content interface{}
		role := string(m.Role)

		switch m.Role {
		case api.MessageRoleToolCall:
			role = "assistant"
			contentBlocks := make([]map[string]interface{}, 0)
			if m.Content != "" {
				contentBlocks = append(contentBlocks, map[string]interface{}{
					"type": "text",
					"text": m.Content,
				})
			}
			for _, toolCall := range m.ToolCalls {
				contentBlocks = append(contentBlocks, map[string]interface{}{
					"type":  "tool_use",
					"id":    toolCall.ID,
					"name":  toolCall.Name,
					"input": toolCall.Parameters,
				})
			}
			content = contentBlocks

		case api.MessageRoleToolResult:
			role = "user"
			contentBlocks := make([]map[string]interface{}, 0)
			for _, result := range m.ToolResults {
				contentBlock := map[string]interface{}{
					"type":        "tool_result",
					"tool_use_id": result.ToolCallID,
					"content":     result.Result,
				}
				contentBlocks = append(contentBlocks, contentBlock)
			}
			content = contentBlocks

		default:
			content = m.Content
		}

		requestMessages = append(requestMessages, ChatCompletionMessage{
			Role:    role,
			Content: content,
		})
	}

	request := ChatCompletionRequest{
		Model:       params.Model,
		Messages:    requestMessages,
		System:      systemMessage,
		MaxTokens:   params.MaxTokens,
		Temperature: params.Temperature,
	}

	if len(params.Toolbox) > 0 {
		request.Tools = convertTools(params.Toolbox)
	}

	var prefill string
	if api.IsAssistantContinuation(messages) {
		prefill = messages[len(messages)-1].Content
	}

	return prefill, request
}

func (c *AnthropicClient) sendRequest(ctx context.Context, r ChatCompletionRequest) (*http.Response, error) {
	jsonData, err := json.Marshal(r)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", c.BaseURL+"/v1/messages", bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("failed to create HTTP request: %w", err)
	}

	req.Header.Set("x-api-key", c.APIKey)
	req.Header.Set("anthropic-version", ANTHROPIC_VERSION)
	req.Header.Set("content-type", "application/json")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}

	if resp.StatusCode != 200 {
		bytes, _ := io.ReadAll(resp.Body)
		return resp, fmt.Errorf("%v", string(bytes))
	}

	return resp, err
}

func (c *AnthropicClient) CreateChatCompletion(
	ctx context.Context,
	params api.RequestParameters,
	messages []api.Message,
) (*api.Message, error) {
	if len(messages) == 0 {
		return nil, fmt.Errorf("can't create completion from no messages")
	}

	_, req := createChatCompletionRequest(params, messages)
	req.Stream = false

	resp, err := c.sendRequest(ctx, req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	var completionResp ChatCompletionResponse
	err = json.NewDecoder(resp.Body).Decode(&completionResp)
	if err != nil {
		return nil, fmt.Errorf("failed to decode response: %w", err)
	}

	return convertResponseToMessage(completionResp)
}

func (c *AnthropicClient) CreateChatCompletionStream(
	ctx context.Context,
	params api.RequestParameters,
	messages []api.Message,
	output chan<- api.Chunk,
) (*api.Message, error) {
	if len(messages) == 0 {
		return nil, fmt.Errorf("can't create completion from no messages")
	}

	prefill, req := createChatCompletionRequest(params, messages)
	req.Stream = true

	resp, err := c.sendRequest(ctx, req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	contentBlocks := make(map[int]*ContentBlock)
	var finalMessage *ChatCompletionResponse

	var firstChunkReceived bool

	reader := bufio.NewReader(resp.Body)
	for {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
			line, err := reader.ReadBytes('\n')
			if err != nil {
				if err == io.EOF {
					break
				}
				return nil, fmt.Errorf("error reading stream: %w", err)
			}

			line = bytes.TrimSpace(line)
			if len(line) == 0 || !bytes.HasPrefix(line, []byte("data: ")) {
				continue
			}

			line = bytes.TrimPrefix(line, []byte("data: "))

			var streamEvent StreamEvent
			err = json.Unmarshal(line, &streamEvent)
			if err != nil {
				return nil, fmt.Errorf("failed to unmarshal stream event: %w", err)
			}

			switch streamEvent.Type {
			case "message_start":
				finalMessage = &ChatCompletionResponse{}
				err = json.Unmarshal(line, &struct {
					Message *ChatCompletionResponse `json:"message"`
				}{Message: finalMessage})
				if err != nil {
					return nil, fmt.Errorf("failed to unmarshal message_start: %w", err)
				}
			case "content_block_start":
				var contentBlockStart struct {
					Index        int          `json:"index"`
					ContentBlock ContentBlock `json:"content_block"`
				}
				err = json.Unmarshal(line, &contentBlockStart)
				if err != nil {
					return nil, fmt.Errorf("failed to unmarshal content_block_start: %w", err)
				}

				contentBlocks[contentBlockStart.Index] = &contentBlockStart.ContentBlock
			case "content_block_delta":
				if streamEvent.Index >= len(contentBlocks) {
					return nil, fmt.Errorf("received delta for non-existent content block index: %d", streamEvent.Index)
				}

				block := contentBlocks[streamEvent.Index]
				delta, ok := streamEvent.Delta.(map[string]interface{})
				if !ok {
					return nil, fmt.Errorf("unexpected delta type: %T", streamEvent.Delta)
				}

				deltaType, ok := delta["type"].(string)
				if !ok {
					return nil, fmt.Errorf("delta missing type field")
				}

				switch deltaType {
				case "text_delta":
					if text, ok := delta["text"].(string); ok {
						if !firstChunkReceived {
							if prefill == "" {
								// if there is no prefil, ensure we trim leading whitespace
								text = strings.TrimSpace(text)
							}
							firstChunkReceived = true
						}
						block.Text += text
						output <- api.Chunk{
							Content:    text,
							TokenCount: 1,
						}
					}
				case "input_json_delta":
					if block.Type != "tool_use" {
						return nil, fmt.Errorf("received input_json_delta for non-tool_use block")
					}
					if partialJSON, ok := delta["partial_json"].(string); ok {
						block.partialJsonAccumulator += partialJSON
					}
				}

			case "content_block_stop":
				if streamEvent.Index >= len(contentBlocks) {
					return nil, fmt.Errorf("received stop for non-existent content block index: %d", streamEvent.Index)
				}

				block := contentBlocks[streamEvent.Index]
				if block.Type == "tool_use" && block.partialJsonAccumulator != "" {
					var inputData map[string]interface{}
					err := json.Unmarshal([]byte(block.partialJsonAccumulator), &inputData)
					if err != nil {
						return nil, fmt.Errorf("failed to unmarshal accumulated JSON for tool use: %w", err)
					}
					block.Input = inputData
				}
			case "message_delta":
				if finalMessage == nil {
					return nil, fmt.Errorf("received message_delta before message_start")
				}
				delta, ok := streamEvent.Delta.(map[string]interface{})
				if !ok {
					return nil, fmt.Errorf("unexpected delta type in message_delta: %T", streamEvent.Delta)
				}
				if stopReason, ok := delta["stop_reason"].(string); ok {
					finalMessage.StopReason = stopReason
				}

			case "message_stop":
				// End of the stream
				goto END_STREAM

			case "error":
				return nil, fmt.Errorf("received error event: %v", streamEvent.Message)

			default:
				// Ignore unknown event types
			}
		}
	}

END_STREAM:
	if finalMessage == nil {
		return nil, fmt.Errorf("no final message received")
	}

	finalMessage.Content = make([]ContentBlock, len(contentBlocks))
	for _, v := range contentBlocks {
		finalMessage.Content = append(finalMessage.Content, *v)
	}

	return convertResponseToMessage(*finalMessage)
}

func convertResponseToMessage(resp ChatCompletionResponse) (*api.Message, error) {
	content := strings.Builder{}
	var toolCalls []api.ToolCall

	for _, block := range resp.Content {
		switch block.Type {
		case "text":
			content.WriteString(block.Text)
		case "tool_use":
			parameters, ok := block.Input.(map[string]interface{})
			if !ok {
				return nil, fmt.Errorf("unexpected type for tool call parameters: %T", block.Input)
			}
			toolCalls = append(toolCalls, api.ToolCall{
				ID:         block.ID,
				Name:       block.Name,
				Parameters: parameters,
			})
		}
	}

	message := &api.Message{
		Role:      api.MessageRoleAssistant,
		Content:   content.String(),
		ToolCalls: toolCalls,
	}

	if len(toolCalls) > 0 {
		message.Role = api.MessageRoleToolCall
	}

	return message, nil
}