package journal

import (
	"context"
	"fmt"
	"net/http"
	"strings"

	"git.golem15.com/golem15/summercms/modules/pact"
)

var _ pact.HasMCP = (*Plugin)(nil)

// mcpGuard is the guard the Journal tools run as: the backend account linked
// to the MCP user (the routes resolve the backend principal themselves).
const mcpGuard = "backend"

// mcpAccessPosts is the permission every Journal tool and the prompt are
// listed with (the routes check it, and access_publish, themselves).
const mcpAccessPosts = "golem15.journal.access_posts"

// mcpListPostsInput is the query of GET /_journal/api/v1/posts.
type mcpListPostsInput struct {
	Page      int    `json:"page,omitempty" query:"page" jsonschema:"the page number, from 1"`
	PerPage   int    `json:"per_page,omitempty" query:"per_page" jsonschema:"posts per page"`
	Search    string `json:"search,omitempty" query:"search" jsonschema:"a phrase of at least three characters the title, slug, excerpt or content contains"`
	Category  string `json:"category,omitempty" query:"category" jsonschema:"a category slug or id"`
	Tag       string `json:"tag,omitempty" query:"tag" jsonschema:"a tag slug or id"`
	Author    string `json:"author,omitempty" query:"author" jsonschema:"the id of the administrator who wrote the posts"`
	Published *bool  `json:"published,omitempty" query:"published" jsonschema:"true for published posts only, false for drafts too (the default for an editor)"`
	Sort      string `json:"sort,omitempty" query:"sort" jsonschema:"the order: a column (published_at, created_at, updated_at, title or id) and optionally asc, for example title asc; newest published first by default"`
}

// mcpShowPostInput names one post by slug.
type mcpShowPostInput struct {
	Slug string `json:"slug" path:"slug" jsonschema:"the post slug"`
}

// mcpCreatePostInput is the body of POST /_journal/api/v1/posts.
type mcpCreatePostInput struct {
	Title       string   `json:"title" jsonschema:"the post title"`
	Content     string   `json:"content" jsonschema:"the post body (Markdown)"`
	Slug        string   `json:"slug,omitempty" jsonschema:"the URL slug; derived from the title when omitted"`
	Excerpt     string   `json:"excerpt,omitempty" jsonschema:"a short summary shown in lists"`
	Published   *bool    `json:"published,omitempty" jsonschema:"publish at once (needs the publish permission); a draft when omitted"`
	PublishedAt string   `json:"published_at,omitempty" jsonschema:"the publication time (RFC 3339 or YYYY-MM-DD)"`
	IsPinned    *bool    `json:"is_pinned,omitempty" jsonschema:"pin the post at the top of lists"`
	Categories  []uint   `json:"categories,omitempty" jsonschema:"category ids"`
	Tags        []string `json:"tags,omitempty" jsonschema:"tag names; unknown tags are created"`
}

// mcpUpdatePostInput is PUT /_journal/api/v1/posts/{id}: only the fields sent
// are changed.
type mcpUpdatePostInput struct {
	ID          uint      `json:"id" path:"id" jsonschema:"the post id"`
	Title       *string   `json:"title,omitempty" jsonschema:"the post title"`
	Content     *string   `json:"content,omitempty" jsonschema:"the post body (Markdown)"`
	Slug        *string   `json:"slug,omitempty" jsonschema:"the URL slug"`
	Excerpt     *string   `json:"excerpt,omitempty" jsonschema:"a short summary shown in lists"`
	Published   *bool     `json:"published,omitempty" jsonschema:"published (needs the publish permission) or a draft"`
	PublishedAt *string   `json:"published_at,omitempty" jsonschema:"the publication time (RFC 3339 or YYYY-MM-DD)"`
	IsPinned    *bool     `json:"is_pinned,omitempty" jsonschema:"pin the post at the top of lists"`
	Categories  *[]uint   `json:"categories,omitempty" jsonschema:"category ids; replaces the post's categories"`
	Tags        *[]string `json:"tags,omitempty" jsonschema:"tag names; replaces the post's tags, unknown tags are created"`
}

// mcpDeletePostInput names one post by id.
type mcpDeletePostInput struct {
	ID uint `json:"id" path:"id" jsonschema:"the post id"`
}

// MCP declares the Journal's MCP tools and prompt (D-15, D-16): the post,
// category and tag routes of /_journal/api/v1, run as the backend account
// linked to the MCP user and listed only when that account has
// golem15.journal.access_posts. The routes enforce their own permissions
// (publishing, other authors' posts) on every call. Media and featured-image
// uploads (multipart) are not tools.
func (p *Plugin) MCP() pact.MCP {
	destructive := true
	return pact.MCP{
		Tools: []pact.MCPTool{
			{
				Name:        "list_posts",
				Title:       "List posts",
				Description: "Lists Journal posts, drafts included, newest first, with filters for a phrase, category, tag and author.",
				Guard:       mcpGuard,
				Method:      http.MethodGet,
				Path:        "/_journal/api/v1/posts",
				Input:       mcpListPostsInput{},
				Permissions: []string{mcpAccessPosts},
			},
			{
				Name:        "show_post",
				Title:       "Show post",
				Description: "Shows one Journal post by slug, a draft included.",
				Guard:       mcpGuard,
				Method:      http.MethodGet,
				Path:        "/_journal/api/v1/posts/{slug}",
				Input:       mcpShowPostInput{},
				Permissions: []string{mcpAccessPosts},
			},
			{
				Name:        "list_categories",
				Title:       "List categories",
				Description: "Lists the Journal categories with their ids and slugs.",
				Guard:       mcpGuard,
				Method:      http.MethodGet,
				Path:        "/_journal/api/v1/categories",
				Input:       struct{}{},
				Permissions: []string{mcpAccessPosts},
			},
			{
				Name:        "list_tags",
				Title:       "List tags",
				Description: "Lists the Journal tags with their ids and slugs.",
				Guard:       mcpGuard,
				Method:      http.MethodGet,
				Path:        "/_journal/api/v1/tags",
				Input:       struct{}{},
				Permissions: []string{mcpAccessPosts},
			},
			{
				Name:        "create_post",
				Title:       "Create post",
				Description: "Creates a Journal post; a draft unless published is true.",
				Guard:       mcpGuard,
				Method:      http.MethodPost,
				Path:        "/_journal/api/v1/posts",
				Input:       mcpCreatePostInput{},
				Permissions: []string{mcpAccessPosts},
			},
			{
				Name:        "update_post",
				Title:       "Update post",
				Description: "Changes the fields sent of one Journal post by id.",
				Guard:       mcpGuard,
				Method:      http.MethodPut,
				Path:        "/_journal/api/v1/posts/{id}",
				Input:       mcpUpdatePostInput{},
				Permissions: []string{mcpAccessPosts},
			},
			{
				Name:        "delete_post",
				Title:       "Delete post",
				Description: "Deletes one Journal post by id.",
				Guard:       mcpGuard,
				Method:      http.MethodDelete,
				Path:        "/_journal/api/v1/posts/{id}",
				Input:       mcpDeletePostInput{},
				Permissions: []string{mcpAccessPosts},
				Destructive: &destructive,
			},
		},
		Prompts: []pact.MCPPrompt{{
			Name:        "draft_post",
			Title:       "Draft a post",
			Description: "Drafts a Journal post on a topic and saves it as a draft.",
			Guard:       mcpGuard,
			Permissions: []string{mcpAccessPosts},
			// It directs journal_create_post, so a read-only grant does
			// not see it.
			Writes: true,
			Arguments: []pact.MCPPromptArgument{
				{Name: "topic", Description: "what the post is about", Required: true},
				{Name: "tone", Description: "the tone of voice, for example friendly or formal"},
			},
			Render: renderDraftPost,
		}},
	}
}

// renderDraftPost builds the draft_post prompt's one user message.
func renderDraftPost(_ context.Context, args map[string]string) ([]pact.MCPPromptMessage, error) {
	topic := strings.TrimSpace(args["topic"])
	if topic == "" {
		return nil, fmt.Errorf("draft_post: topic is required")
	}
	tone := strings.TrimSpace(args["tone"])
	if tone == "" {
		tone = "clear and friendly"
	}
	text := "Write a Journal post about: " + topic + "\n\n" +
		"Tone: " + tone + ".\n" +
		"Style: a short, specific title; an excerpt of one or two sentences; the body in Markdown with short paragraphs and subheadings where they help; no filler.\n" +
		"Before writing, call journal_list_categories and journal_list_tags and reuse fitting categories and tags.\n" +
		"Then save it with journal_create_post with published set to false, so an editor reviews the draft before it goes live, and reply with the new post's slug."
	return []pact.MCPPromptMessage{{Role: "user", Text: text}}, nil
}