package google

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

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

type Client struct {
	APIKey  string
	BaseURL string
}

type ContentPart struct {
	Text         string            `json:"text,omitempty"`
	FunctionCall *FunctionCall     `json:"functionCall,omitempty"`
	FunctionResp *FunctionResponse `json:"functionResponse,omitempty"`
}

type FunctionCall struct {
	Name string            `json:"name"`
	Args map[string]string `json:"args"`
}

type FunctionResponse struct {
	Name     string      `json:"name"`
	Response interface{} `json:"response"`
}

type Content struct {
	Role  string        `json:"role"`
	Parts []ContentPart `json:"parts"`
}

type GenerationConfig struct {
	MaxOutputTokens *int     `json:"maxOutputTokens,omitempty"`
	Temperature     *float32 `json:"temperature,omitempty"`
	TopP            *float32 `json:"topP,omitempty"`
	TopK            *int     `json:"topK,omitempty"`
}

type GenerateContentRequest struct {
	Contents          []Content         `json:"contents"`
	Tools             []Tool            `json:"tools,omitempty"`
	SystemInstruction *Content          `json:"systemInstruction,omitempty"`
	GenerationConfig  *GenerationConfig `json:"generationConfig,omitempty"`
}

type Candidate struct {
	Content      Content `json:"content"`
	FinishReason string  `json:"finishReason"`
	Index        int     `json:"index"`
}

type UsageMetadata struct {
	PromptTokenCount     int `json:"promptTokenCount"`
	CandidatesTokenCount int `json:"candidatesTokenCount"`
	TotalTokenCount      int `json:"totalTokenCount"`
}

type GenerateContentResponse struct {
	Candidates    []Candidate   `json:"candidates"`
	UsageMetadata UsageMetadata `json:"usageMetadata"`
}

type Tool struct {
	FunctionDeclarations []FunctionDeclaration `json:"functionDeclarations"`
}

type FunctionDeclaration struct {
	Name        string         `json:"name"`
	Description string         `json:"description"`
	Parameters  ToolParameters `json:"parameters"`
}

type ToolParameters struct {
	Type       string                   `json:"type"`
	Properties map[string]ToolParameter `json:"properties,omitempty"`
	Required   []string                 `json:"required,omitempty"`
}

type ToolParameter struct {
	Type        string   `json:"type"`
	Description string   `json:"description"`
	Values      []string `json:"values,omitempty"`
}

func convertTools(tools []api.ToolSpec) []Tool {
	geminiTools := make([]Tool, len(tools))
	for i, tool := range tools {
		params := make(map[string]ToolParameter)
		var required []string

		for _, param := range tool.Parameters {
			// TODO: proper enum handing
			params[param.Name] = ToolParameter{
				Type:        param.Type,
				Description: param.Description,
				Values:      param.Enum,
			}
			if param.Required {
				required = append(required, param.Name)
			}
		}

		geminiTools[i] = Tool{
			FunctionDeclarations: []FunctionDeclaration{
				{
					Name:        tool.Name,
					Description: tool.Description,
					Parameters: ToolParameters{
						Type:       "OBJECT",
						Properties: params,
						Required:   required,
					},
				},
			},
		}
	}
	return geminiTools
}

func convertToolCallToGemini(toolCalls []api.ToolCall) []ContentPart {
	converted := make([]ContentPart, len(toolCalls))
	for i, call := range toolCalls {
		args := make(map[string]string)
		for k, v := range call.Parameters {
			args[k] = fmt.Sprintf("%v", v)
		}
		converted[i].FunctionCall = &FunctionCall{
			Name: call.Name,
			Args: args,
		}
	}
	return converted
}

func convertToolCallToAPI(functionCalls []FunctionCall) []api.ToolCall {
	converted := make([]api.ToolCall, len(functionCalls))
	for i, call := range functionCalls {
		params := make(map[string]interface{})
		for k, v := range call.Args {
			params[k] = v
		}
		converted[i].Name = call.Name
		converted[i].Parameters = params
	}
	return converted
}

func convertToolResultsToGemini(toolResults []api.ToolResult) ([]FunctionResponse, error) {
	results := make([]FunctionResponse, len(toolResults))
	for i, result := range toolResults {
		var obj interface{}
		err := json.Unmarshal([]byte(result.Result), &obj)
		if err != nil {
			return nil, fmt.Errorf("Could not unmarshal %s: %v", result.Result, err)
		}
		results[i] = FunctionResponse{
			Name:     result.ToolName,
			Response: obj,
		}
	}
	return results, nil
}

func createGenerateContentRequest(
	params api.RequestParameters,
	messages []api.Message,
) (*GenerateContentRequest, error) {
	requestContents := make([]Content, 0, len(messages))

	startIdx := 0
	var system string
	if len(messages) > 0 && messages[0].Role == api.MessageRoleSystem {
		system = messages[0].Content
		startIdx = 1
	}

	for _, m := range messages[startIdx:] {
		switch m.Role {
		case "tool_call":
			content := Content{
				Role:  "model",
				Parts: convertToolCallToGemini(m.ToolCalls),
			}
			requestContents = append(requestContents, content)
		case "tool_result":
			results, err := convertToolResultsToGemini(m.ToolResults)
			if err != nil {
				return nil, err
			}
			// expand tool_result messages' results into multiple gemini messages
			for _, result := range results {
				content := Content{
					Role: "function",
					Parts: []ContentPart{
						{
							FunctionResp: &result,
						},
					},
				}
				requestContents = append(requestContents, content)
			}
		default:
			var role string
			switch m.Role {
			case api.MessageRoleAssistant:
				role = "model"
			case api.MessageRoleUser:
				role = "user"
			}

			if role == "" {
				panic("Unhandled role: " + m.Role)
			}

			content := Content{
				Role: role,
				Parts: []ContentPart{
					{
						Text: m.Content,
					},
				},
			}
			requestContents = append(requestContents, content)
		}
	}

	request := &GenerateContentRequest{
		Contents: requestContents,
		GenerationConfig: &GenerationConfig{
			MaxOutputTokens: &params.MaxTokens,
			Temperature:     &params.Temperature,
			TopP:            &params.TopP,
		},
	}

	if system != "" {
		request.SystemInstruction = &Content{
			Parts: []ContentPart{
				{
					Text: system,
				},
			},
		}
	}

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

	return request, nil
}

func (c *Client) sendRequest(req *http.Request) (*http.Response, error) {
	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 *Client) 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, err := createGenerateContentRequest(params, messages)
	if err != nil {
		return nil, err
	}
	jsonData, err := json.Marshal(req)
	if err != nil {
		return nil, err
	}

	url := fmt.Sprintf(
		"%s/v1beta/models/%s:generateContent?key=%s",
		c.BaseURL, params.Model, c.APIKey,
	)
	httpReq, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, err
	}

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

	var completionResp GenerateContentResponse
	err = json.NewDecoder(resp.Body).Decode(&completionResp)
	if err != nil {
		return nil, err
	}

	choice := completionResp.Candidates[0]

	var content string
	lastMessage := messages[len(messages)-1]
	if lastMessage.Role.IsAssistant() {
		content = lastMessage.Content
	}

	var toolCalls []FunctionCall
	for _, part := range choice.Content.Parts {
		if part.Text != "" {
			content += part.Text
		}

		if part.FunctionCall != nil {
			toolCalls = append(toolCalls, *part.FunctionCall)
		}
	}

	if len(toolCalls) > 0 {
		return &api.Message{
			Role:      api.MessageRoleToolCall,
			Content:   content,
			ToolCalls: convertToolCallToAPI(toolCalls),
		}, nil
	}

	return &api.Message{
		Role:    api.MessageRoleAssistant,
		Content: content,
	}, nil
}

func (c *Client) 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")
	}

	req, err := createGenerateContentRequest(params, messages)
	if err != nil {
		return nil, err
	}
	jsonData, err := json.Marshal(req)
	if err != nil {
		return nil, err
	}

	url := fmt.Sprintf(
		"%s/v1beta/models/%s:streamGenerateContent?key=%s&alt=sse",
		c.BaseURL, params.Model, c.APIKey,
	)
	httpReq, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, err
	}

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

	content := strings.Builder{}

	lastMessage := messages[len(messages)-1]
	if lastMessage.Role.IsAssistant() {
		content.WriteString(lastMessage.Content)
	}

	var toolCalls []FunctionCall

	reader := bufio.NewReader(resp.Body)

	lastTokenCount := 0
	for {
		line, err := reader.ReadBytes('\n')
		if err != nil {
			if err == io.EOF {
				break
			}
			return nil, err
		}

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

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

		var resp GenerateContentResponse
		err = json.Unmarshal(line, &resp)
		if err != nil {
			return nil, err
		}

		tokens := resp.UsageMetadata.CandidatesTokenCount - lastTokenCount
		lastTokenCount += tokens

		choice := resp.Candidates[0]
		for _, part := range choice.Content.Parts {
			if part.FunctionCall != nil {
				toolCalls = append(toolCalls, *part.FunctionCall)
			} else if part.Text != "" {
				output <- api.Chunk{
					Content:    part.Text,
					TokenCount: uint(tokens),
				}
				content.WriteString(part.Text)
			}
		}
	}

	// If there are function calls, handle them and recurse
	if len(toolCalls) > 0 {
		return &api.Message{
			Role:      api.MessageRoleToolCall,
			Content:   content.String(),
			ToolCalls: convertToolCallToAPI(toolCalls),
		}, nil
	}

	return &api.Message{
		Role:    api.MessageRoleAssistant,
		Content: content.String(),
	}, nil
}