package mcp

import (
	"encoding/json"
	"fmt"

	"git.k6n.net/mats/go-cart-actor/pkg/promotions"
	pmcp "git.k6n.net/mats/platform/mcp"
)

// AdminTool is one admin promotion tool definition — name, description, input
// schema, and the invoke function. It mirrors cmsmount.MCPTool but lives in
// this package so the promotions module doesn't import the CMS module.
type AdminTool struct {
	Name        string
	Description string
	InputSchema json.RawMessage
	Invoke      func(args json.RawMessage) (any, error)
}

// AdminTools returns the admin-only promotion MCP tool definitions (upsert,
// set_status, delete). Pass these to cmsmount.AddMCPTools to merge them into
// the CMS MCP behind full auth.
func AdminTools(store *promotions.Store, eval *promotions.PromotionService) []AdminTool {
	if eval == nil {
		eval = promotions.NewPromotionService(nil)
	}
	return []AdminTool{
		{
			Name: "upsert_promotion",
			Description: "Create a promotion or replace the existing one with the same id. " +
				"`promotion` is a full promotion-rule object (id, name, status, priority, conditions, actions). " +
				"For a tiered volume discount (Volymrabatt) use a cart_total condition plus a tiered_discount action " +
				"whose config.tiers each have minTotal/maxTotal (öre incl. VAT) and percent.",
			InputSchema: pmcp.Object(pmcp.Props{
				"promotion": pmcp.ObjectValue("the full promotion rule object"),
			}, []string{"promotion"}),
			Invoke: func(args json.RawMessage) (any, error) {
				var a struct {
					Promotion json.RawMessage `json:"promotion"`
				}
				if err := pmcp.Decode(args, &a); err != nil {
					return nil, err
				}
				var rule promotions.PromotionRule
				if err := json.Unmarshal(a.Promotion, &rule); err != nil {
					return nil, fmt.Errorf("invalid promotion: %w", err)
				}
				if rule.ID == "" {
					return nil, fmt.Errorf("promotion.id is required")
				}
				if rule.Status == "" {
					rule.Status = promotions.StatusActive
				}
				replaced, err := store.Upsert(rule)
				if err != nil {
					return nil, err
				}
				return map[string]any{"id": rule.ID, "replaced": replaced}, nil
			},
		},
		{
			Name:        "set_promotion_status",
			Description: "Set a promotion's status (active|inactive|scheduled|expired) to toggle it on or off.",
			InputSchema: pmcp.Object(pmcp.Props{
				"id":     pmcp.String("the promotion id"),
				"status": pmcp.String("new status: active|inactive|scheduled|expired"),
			}, []string{"id", "status"}),
			Invoke: func(args json.RawMessage) (any, error) {
				var a struct {
					ID     string `json:"id"`
					Status string `json:"status"`
				}
				if err := pmcp.Decode(args, &a); err != nil {
					return nil, err
				}
				if !validStatus(a.Status) {
					return nil, fmt.Errorf("invalid status %q", a.Status)
				}
				found, err := store.SetStatus(a.ID, promotions.PromotionStatus(a.Status))
				if err != nil {
					return nil, err
				}
				if !found {
					return nil, fmt.Errorf("promotion %q not found", a.ID)
				}
				return map[string]any{"id": a.ID, "status": a.Status}, nil
			},
		},
		{
			Name:        "delete_promotion",
			Description: "Delete a promotion rule by id.",
			InputSchema: pmcp.Object(pmcp.Props{"id": pmcp.String("the promotion id")}, []string{"id"}),
			Invoke: func(args json.RawMessage) (any, error) {
				var a struct {
					ID string `json:"id"`
				}
				if err := pmcp.Decode(args, &a); err != nil {
					return nil, err
				}
				found, err := store.Delete(a.ID)
				if err != nil {
					return nil, err
				}
				if !found {
					return nil, fmt.Errorf("promotion %q not found", a.ID)
				}
				return map[string]any{"id": a.ID, "deleted": true}, nil
			},
		},
	}
}