package cli

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"strings"

	openai "github.com/sashabaranov/go-openai"
)

func CreateChatCompletionRequest(model string, messages []Message, maxTokens int) openai.ChatCompletionRequest {
	chatCompletionMessages := []openai.ChatCompletionMessage{}
	for _, m := range messages {
		message := openai.ChatCompletionMessage{
			Role:    m.Role,
			Content: m.OriginalContent,
		}
		if m.ToolCallID.Valid {
			message.ToolCallID = m.ToolCallID.String
		}
		if m.ToolCalls.Valid {
			// unmarshal directly into chatMessage.ToolCalls
			err := json.Unmarshal([]byte(m.ToolCalls.String), &message.ToolCalls)
			if err != nil {
				// TODO: handle, this shouldn't really happen since
				// we only save the successfully marshal'd data to database
				fmt.Printf("Error unmarshalling the tool_calls JSON: %v\n", err)
			}
		}
		chatCompletionMessages = append(chatCompletionMessages, message)
	}

	var tools []openai.Tool
	for _, t := range AvailableTools {
		// TODO: support some way to limit which tools are available per-request
		tools = append(tools, t.Tool)
	}

	return openai.ChatCompletionRequest{
		Model:      model,
		Messages:   chatCompletionMessages,
		MaxTokens:  maxTokens,
		N:          1, // limit responses to 1 "choice". we use choices[0] to reference it
		Tools:      tools,
		ToolChoice: "auto", // TODO: allow limiting/forcing which function is called?
	}
}

// CreateChatCompletion submits a Chat Completion API request and returns the
// response. CreateChatCompletion will recursively call itself in the case of
// tool calls, until a response is received with the final user-facing output.
func CreateChatCompletion(model string, messages []Message, maxTokens int) (string, error) {
	client := openai.NewClient(*config.OpenAI.APIKey)
	req := CreateChatCompletionRequest(model, messages, maxTokens)
	resp, err := client.CreateChatCompletion(context.Background(), req)
	if err != nil {
		return "", err
	}

	choice := resp.Choices[0]

	if len(choice.Message.ToolCalls) > 0 {
		if choice.Message.Content != "" {
			return "", fmt.Errorf("Model replied with user-facing content in addition to tool calls. Unsupported.")
		}

		// Append the assistant's reply with its request for tool calls
		toolCallJson, _ := json.Marshal(choice.Message.ToolCalls)
		messages = append(messages, Message{
			Role:      "assistant",
			ToolCalls: sql.NullString{String: string(toolCallJson), Valid: true},
		})

		toolReplies, err := ExecuteToolCalls(choice.Message.ToolCalls)
		if err != nil {
			return "", err
		}

		// Recurse into CreateChatCompletion with the tool call replies added
		// to the original messages
		return CreateChatCompletion(model, append(messages, toolReplies...), maxTokens)
	}

	// Return the user-facing message.
	return choice.Message.Content, nil
}

// CreateChatCompletionStream submits a streaming Chat Completion API request
// and both returns and streams the response to the provided output channel.
// May return a partial response if an error occurs mid-stream.
func CreateChatCompletionStream(model string, messages []Message, maxTokens int, output chan<- string) (string, error) {
	client := openai.NewClient(*config.OpenAI.APIKey)
	req := CreateChatCompletionRequest(model, messages, maxTokens)

	stream, err := client.CreateChatCompletionStream(context.Background(), req)
	if err != nil {
		return "", err
	}
	defer stream.Close()

	content := strings.Builder{}
	toolCalls := []openai.ToolCall{}

	// Iterate stream segments
	for {
		response, e := stream.Recv()
		if errors.Is(e, io.EOF) {
			break
		}

		if e != nil {
			err = e
			break
		}

		delta := response.Choices[0].Delta
		if len(delta.ToolCalls) > 0 {
			// Construct streamed tool_call arguments
			for _, tc := range delta.ToolCalls {
				if tc.Index == nil {
					return "", fmt.Errorf("Unexpected nil index for streamed tool call.")
				}
				if len(toolCalls) <= *tc.Index {
					toolCalls = append(toolCalls, tc)
				} else {
					toolCalls[*tc.Index].Function.Arguments += tc.Function.Arguments
				}
			}
		} else {
			output <- delta.Content
			content.WriteString(delta.Content)
		}
	}

	if len(toolCalls) > 0 {
		if content.String() != "" {
			return "", fmt.Errorf("Model replied with user-facing content in addition to tool calls. Unsupported.")
		}

		// Append the assistant's reply with its request for tool calls
		toolCallJson, _ := json.Marshal(toolCalls)
		messages = append(messages, Message{
			Role:      "assistant",
			ToolCalls: sql.NullString{String: string(toolCallJson), Valid: true},
		})

		toolReplies, err := ExecuteToolCalls(toolCalls)
		if err != nil {
			return "", err
		}

		// Recurse into CreateChatCompletionStream with the tool call replies
		// added to the original messages
		return CreateChatCompletionStream(model, append(messages, toolReplies...), maxTokens, output)
	}

	return content.String(), err
}