package anthropic

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

	"git.mlow.ca/mlow/lmcli/pkg/lmcli/model"
	"git.mlow.ca/mlow/lmcli/pkg/lmcli/provider"
	"git.mlow.ca/mlow/lmcli/pkg/lmcli/tools"
)

type AnthropicClient struct {
	APIKey string
}

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

type Request struct {
	Model         string    `json:"model"`
	Messages      []Message `json:"messages"`
	System        string    `json:"system,omitempty"`
	MaxTokens     int       `json:"max_tokens,omitempty"`
	StopSequences []string  `json:"stop_sequences,omitempty"`
	Stream        bool      `json:"stream,omitempty"`
	Temperature   float32   `json:"temperature,omitempty"`
	//TopP          float32   `json:"top_p,omitempty"`
	//TopK          float32   `json:"top_k,omitempty"`
}

type OriginalContent struct {
	Type string `json:"type"`
	Text string `json:"text"`
}

type Response struct {
	Id      string            `json:"id"`
	Type    string            `json:"type"`
	Role    string            `json:"role"`
	Content []OriginalContent `json:"content"`
}

const FUNCTION_STOP_SEQUENCE = "</function_calls>"

func buildRequest(params model.RequestParameters, messages []model.Message) Request {
	requestBody := Request{
		Model:       params.Model,
		Messages:    make([]Message, len(messages)),
		System:      params.SystemPrompt,
		MaxTokens:   params.MaxTokens,
		Temperature: params.Temperature,
		Stream:      false,

		StopSequences: []string{
			FUNCTION_STOP_SEQUENCE,
			"\n\nHuman:",
		},
	}

	startIdx := 0
	if len(messages) > 0 && messages[0].Role == model.MessageRoleSystem {
		requestBody.System = messages[0].Content
		requestBody.Messages = requestBody.Messages[1:]
		startIdx = 1
	}

	if len(params.ToolBag) > 0 {
		if len(requestBody.System) > 0 {
			// add a divider between existing system prompt and tools
			requestBody.System += "\n\n---\n\n"
		}
		requestBody.System += buildToolsSystemPrompt(params.ToolBag)
	}

	for i, msg := range messages[startIdx:] {
		message := &requestBody.Messages[i]

		switch msg.Role {
		case model.MessageRoleToolCall:
			message.Role = "assistant"
			if msg.Content != "" {
				message.Content = msg.Content
			}
			xmlFuncCalls := convertToolCallsToXMLFunctionCalls(msg.ToolCalls)
			xmlString, err := xmlFuncCalls.XMLString()
			if err != nil {
				panic("Could not serialize []ToolCall to XMLFunctionCall")
			}
			if len(message.Content) > 0 {
				message.Content += fmt.Sprintf("\n\n%s", xmlString)
			} else {
				message.Content = xmlString
			}
		case model.MessageRoleToolResult:
			xmlFuncResults := convertToolResultsToXMLFunctionResult(msg.ToolResults)
			xmlString, err := xmlFuncResults.XMLString()
			if err != nil {
				panic("Could not serialize []ToolResult to XMLFunctionResults")
			}
			message.Role = "user"
			message.Content = xmlString
		default:
			message.Role = string(msg.Role)
			message.Content = msg.Content
		}
	}
	return requestBody
}

func sendRequest(ctx context.Context, c *AnthropicClient, r Request) (*http.Response, error) {
	url := "https://api.anthropic.com/v1/messages"

	jsonBody, err := json.Marshal(r)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request body: %v", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonBody))
	if err != nil {
		return nil, fmt.Errorf("failed to create HTTP request: %v", err)
	}

	req.Header.Set("x-api-key", c.APIKey)
	req.Header.Set("anthropic-version", "2023-06-01")
	req.Header.Set("content-type", "application/json")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send HTTP request: %v", err)
	}

	return resp, nil
}

func (c *AnthropicClient) CreateChatCompletion(
	ctx context.Context,
	params model.RequestParameters,
	messages []model.Message,
	callback provider.ReplyCallback,
) (string, error) {
	request := buildRequest(params, messages)

	resp, err := sendRequest(ctx, c, request)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

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

	sb := strings.Builder{}
	for _, content := range response.Content {
		var reply model.Message
		switch content.Type {
		case "text":
			reply = model.Message{
				Role:    model.MessageRoleAssistant,
				Content: content.Text,
			}
			sb.WriteString(reply.Content)
		default:
			return "", fmt.Errorf("unsupported message type: %s", content.Type)
		}
		if callback != nil {
			callback(reply)
		}
	}

	return sb.String(), nil
}

func (c *AnthropicClient) CreateChatCompletionStream(
	ctx context.Context,
	params model.RequestParameters,
	messages []model.Message,
	callback provider.ReplyCallback,
	output chan<- string,
) (string, error) {
	request := buildRequest(params, messages)
	request.Stream = true

	resp, err := sendRequest(ctx, c, request)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	scanner := bufio.NewScanner(resp.Body)
	sb := strings.Builder{}

	isToolCall := false

	for scanner.Scan() {
		line := scanner.Text()
		line = strings.TrimSpace(line)

		if len(line) == 0 {
			continue
		}

		if line[0] == '{' {
			var event map[string]interface{}
			err := json.Unmarshal([]byte(line), &event)
			if err != nil {
				return "", fmt.Errorf("failed to unmarshal event data '%s': %v", line, err)
			}
			eventType, ok := event["type"].(string)
			if !ok {
				return "", fmt.Errorf("invalid event: %s", line)
			}
			switch eventType {
			case "error":
				return sb.String(), fmt.Errorf("an error occurred: %s", event["error"])
			default:
				return sb.String(), fmt.Errorf("unknown event type: %s", eventType)
			}
		} else if strings.HasPrefix(line, "data:") {
			data := strings.TrimSpace(strings.TrimPrefix(line, "data:"))
			var event map[string]interface{}
			err := json.Unmarshal([]byte(data), &event)
			if err != nil {
				return "", fmt.Errorf("failed to unmarshal event data: %v", err)
			}

			eventType, ok := event["type"].(string)
			if !ok {
				return "", fmt.Errorf("invalid event type")
			}

			switch eventType {
			case "message_start":
				// noop
			case "ping":
				// write an empty string to signal start of text
				output <- ""
			case "content_block_start":
				// ignore?
			case "content_block_delta":
				delta, ok := event["delta"].(map[string]interface{})
				if !ok {
					return "", fmt.Errorf("invalid content block delta")
				}
				text, ok := delta["text"].(string)
				if !ok {
					return "", fmt.Errorf("invalid text delta")
				}
				sb.WriteString(text)
				output <- text
			case "content_block_stop":
				// ignore?
			case "message_delta":
				delta, ok := event["delta"].(map[string]interface{})
				if !ok {
					return "", fmt.Errorf("invalid message delta")
				}
				stopReason, ok := delta["stop_reason"].(string)
				if ok && stopReason == "stop_sequence" {
					stopSequence, ok := delta["stop_sequence"].(string)
					if ok && stopSequence == FUNCTION_STOP_SEQUENCE {
						content := sb.String()

						start := strings.Index(content, "<function_calls>")
						if start == -1 {
							return content, fmt.Errorf("reached </function_calls> stop sequence but no opening tag found")
						}

						isToolCall = true

						funcCallXml := content[start:]
						funcCallXml += FUNCTION_STOP_SEQUENCE

						sb.WriteString(FUNCTION_STOP_SEQUENCE)
						output <- FUNCTION_STOP_SEQUENCE

						// Extract function calls
						var functionCalls XMLFunctionCalls
						err := xml.Unmarshal([]byte(sb.String()), &functionCalls)
						if err != nil {
							return "", fmt.Errorf("failed to unmarshal function_calls: %v", err)
						}

						// Execute function calls
						toolCall := model.Message{
							Role: model.MessageRoleToolCall,
							// xml stripped from content
							Content:   content[:start],
							ToolCalls: convertXMLFunctionCallsToToolCalls(functionCalls),
						}

						toolResults, err := tools.ExecuteToolCalls(toolCall.ToolCalls, params.ToolBag)
						if err != nil {
							return "", err
						}

						toolReply := model.Message{
							Role:        model.MessageRoleToolResult,
							ToolResults: toolResults,
						}

						if callback != nil {
							callback(toolCall)
							callback(toolReply)
						}

						// Recurse into CreateChatCompletionStream with the tool call replies
						// added to the original messages
						messages = append(append(messages, toolCall), toolReply)
						return c.CreateChatCompletionStream(ctx, params, messages, callback, output)
					}
				}
			case "message_stop":
				// return the completed message
				if callback != nil {
					if !isToolCall {
						callback(model.Message{
							Role:    model.MessageRoleAssistant,
							Content: sb.String(),
						})
					}
				}
				return sb.String(), nil
			case "error":
				return sb.String(), fmt.Errorf("an error occurred: %s", event["error"])
			default:
				fmt.Printf("\nUnrecognized event: %s\n", data)
			}
		}
	}

	if err := scanner.Err(); err != nil {
		return "", fmt.Errorf("failed to read response body: %v", err)
	}

	return "", fmt.Errorf("unexpected end of stream")
}