// Package llm provides an OpenAI-compatible client for LLM interactions.
// It handles chat completions with automatic tool call execution.
package llm

import (
	"context"
	"fmt"
	"log/slog"
	"strings"
	"time"

	"raven/internal/message"
	"raven/internal/tool"

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

// Config holds the configuration for an LLM client.
type Config struct {
	// Key is the API key for authentication.
	Key string `yaml:"key"`
	// Model is the model identifier (e.g., "gpt-oss-120b", "qwen3-32b").
	Model string `yaml:"model"`
	// SystemPrompt is prepended to all conversations.
	SystemPrompt string `yaml:"system_prompt"`
	// Timeout is the maximum duration for a query (e.g., "15m").
	// Defaults to 15 minutes if empty.
	Timeout string `yaml:"timeout"`
	// URL is the base URL of the OpenAI-compatible API endpoint.
	URL string `yaml:"url"`
}

// Validate checks that required configuration values are present and valid.
func (cfg Config) Validate() error {
	if cfg.Model == "" {
		return fmt.Errorf("missing model")
	}
	if cfg.Timeout != "" {
		if _, err := time.ParseDuration(cfg.Timeout); err != nil {
			return fmt.Errorf("invalid duration")
		}
	}
	if cfg.URL == "" {
		return fmt.Errorf("missing URL")
	}

	return nil
}

// Client wraps an OpenAI-compatible client with tool execution support.
type Client struct {
	client       *openai.Client
	log          *slog.Logger
	model        string
	registry     *tool.Registry
	systemPrompt string
	timeout      time.Duration
	tools        []openai.Tool
}

// NewClient creates a new LLM client with the provided configuration.
// The registry is optional; if nil, tool calling is disabled.
func NewClient(
	cfg Config,
	registry *tool.Registry,
	log *slog.Logger,
) (*Client, error) {
	if err := cfg.Validate(); err != nil {
		return nil, fmt.Errorf("invalid config: %v", err)
	}
	var llm = &Client{
		log:          log,
		model:        cfg.Model,
		systemPrompt: cfg.SystemPrompt,
		registry:     registry,
	}
	if cfg.Timeout == "" {
		llm.timeout = time.Duration(15 * time.Minute)
	} else {
		d, err := time.ParseDuration(cfg.Timeout)
		if err != nil {
			return nil, fmt.Errorf("parse timeout: %v", err)
		}
		llm.timeout = d
	}

	// Setup client.
	clientConfig := openai.DefaultConfig(cfg.Key)
	clientConfig.BaseURL = cfg.URL
	llm.client = openai.NewClientWithConfig(clientConfig)

	// Parse tools.
	if llm.registry != nil {
		for _, name := range llm.registry.List() {
			tool, _ := llm.registry.Get(name)
			llm.tools = append(llm.tools, tool.OpenAI())
		}
	}

	return llm, nil
}

// Query sends a message to the LLM and returns its response.
// It automatically executes any tool calls requested by the model,
// looping until the model returns a final text response.
// Supports multimodal content (text and images) via the Message type.
func (c *Client) Query(
	ctx context.Context, msg *message.Message,
) (string, error) {
	ctx, cancel := context.WithTimeout(ctx, c.timeout)
	defer cancel()

	// Build user message from email content.
	// Uses MultiContent to support both text and image parts.
	userMessage := openai.ChatCompletionMessage{
		Role:         openai.ChatMessageRoleUser,
		MultiContent: msg.ToOpenAIMessages(),
	}

	// Set the system message and the user prompt.
	messages := []openai.ChatCompletionMessage{
		{
			Role:    openai.ChatMessageRoleSystem,
			Content: c.systemPrompt,
		},
		userMessage,
	}

	// Loop for tool calls.
	for {
		req := openai.ChatCompletionRequest{
			Model:    c.model,
			Messages: messages,
		}
		if len(c.tools) > 0 {
			req.Tools = c.tools
		}

		res, err := c.client.CreateChatCompletion(ctx, req)
		if err != nil {
			return "", fmt.Errorf("chat completion: %w", err)
		}
		if len(res.Choices) == 0 {
			return "", fmt.Errorf("no response choices returned")
		}

		choice := res.Choices[0]
		message := choice.Message

		// If no tool calls, we're done.
		if len(message.ToolCalls) == 0 {
			return message.Content, nil
		}

		// Add assistant message with tool calls to history.
		messages = append(messages, message)

		// Process each tool call.
		for _, tc := range message.ToolCalls {
			c.log.InfoContext(
				ctx,
				"calling tool",
				slog.String("name", tc.Function.Name),
				slog.String("args", tc.Function.Arguments),
			)

			res, err := c.registry.Execute(
				ctx, tc.Function.Name, tc.Function.Arguments,
			)
			if err != nil {
				// Return error to LLM so it can recover.
				c.log.Error(
					"failed to call tool",
					slog.Any("error", err),
					slog.String("name", tc.Function.Name),
				)
				// Assume JSON is a more helpful response
				// for an LLM.
				res = fmt.Sprintf(
					`{"ok": false,"error": %q}`, err,
				)
			} else {
				c.log.Info(
					"called tool",
					slog.String("name", tc.Function.Name),
				)
			}

			// Content cannot be empty.
			// Assume JSON is better than OK or (no output).
			if strings.TrimSpace(res) == "" {
				res = `{"ok":true,"result":null}`
			}

			// Add tool result to messages.
			messages = append(
				messages,
				openai.ChatCompletionMessage{
					Role:       openai.ChatMessageRoleTool,
					Content:    res,
					ToolCallID: tc.ID,
				},
			)
		}
		// Loop to get LLM's response after tool execution.
	}
}