package mcp

import (
	"context"
	"fmt"

	"github.com/google/uuid"
	mcpsdk "github.com/modelcontextprotocol/go-sdk/mcp"
)

// registerChatTools 注册 chat 相关 MCP 工具。
// MVP 只有一个：list_recent_messages。
func registerChatTools(srv *mcpsdk.Server, deps ServerDeps) {
	registerListRecentMessages(srv, deps)
}

type listRecentMessagesIn struct {
	ConversationID string `json:"conversation_id" jsonschema:"required,description=UUID of the conversation"`
	BeforeID       *int64 `json:"before_id,omitempty" jsonschema:"description=Cursor: return messages with ID < this value"`
	Limit          int    `json:"limit,omitempty" jsonschema:"description=Max messages to return (default 50, max 200)"`
}
type messageSummary struct {
	ID        int64  `json:"id"`
	Role      string `json:"role"`
	Content   string `json:"content"`
	Status    string `json:"status"`
	CreatedAt string `json:"created_at"`
}
type listRecentMessagesOut struct {
	Messages []messageSummary `json:"messages"`
}

func registerListRecentMessages(srv *mcpsdk.Server, deps ServerDeps) {
	mcpsdk.AddTool(srv,
		&mcpsdk.Tool{Name: "list_recent_messages", Description: "List recent chat messages in a conversation."},
		func(ctx context.Context, _ *mcpsdk.CallToolRequest, in listRecentMessagesIn) (*mcpsdk.CallToolResult, listRecentMessagesOut, error) {
			if err := CheckToolFromCtx(ctx, "list_recent_messages"); err != nil {
				return nil, listRecentMessagesOut{}, err
			}
			c, err := deps.Caller.Resolve(ctx)
			if err != nil {
				return nil, listRecentMessagesOut{}, err
			}

			convID, err := uuid.Parse(in.ConversationID)
			if err != nil {
				return nil, listRecentMessagesOut{}, fmt.Errorf("invalid conversation_id: %w", err)
			}

			limit := in.Limit
			if limit <= 0 {
				limit = 50
			}
			if limit > 200 {
				limit = 200
			}

			msgs, err := deps.Messages.ListMessages(ctx, c.UserID, convID, in.BeforeID, limit)
			if err != nil {
				return nil, listRecentMessagesOut{}, err
			}

			out := listRecentMessagesOut{Messages: make([]messageSummary, 0, len(msgs))}
			for _, m := range msgs {
				out.Messages = append(out.Messages, messageSummary{
					ID:        m.ID,
					Role:      string(m.Role),
					Content:   m.Content,
					Status:    string(m.Status),
					CreatedAt: m.CreatedAt.Format("2006-01-02T15:04:05Z07:00"),
				})
			}
			return nil, out, nil
		})
}