package api

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// Comment is the public representation of a Confluence comment thread node.
//
// BodyStorage is the raw Confluence storage XML for the comment body; it is not
// converted to Markdown. Replies are nested up to two levels deep (the depth
// supported by the children.comment expand chain); deeper threads are not
// captured.
type Comment struct {
	ID          string     `json:"id"`
	Title       string     `json:"title,omitempty"`
	Status      string     `json:"status,omitempty"`
	Location    string     `json:"location"`
	MarkerRef   string     `json:"marker_ref,omitempty"`
	Resolved    bool       `json:"resolved,omitempty"`
	Resolution  string     `json:"resolution,omitempty"`
	Author      User       `json:"author"`
	Created     time.Time  `json:"created"`
	Updated     time.Time  `json:"updated,omitempty"`
	BodyStorage string     `json:"body_storage"`
	Replies     []*Comment `json:"replies,omitempty"`
}

// User identifies a Confluence user attached to a comment.
type User struct {
	Username    string `json:"username,omitempty"`
	DisplayName string `json:"display_name,omitempty"`
	UserKey     string `json:"user_key,omitempty"`
	AccountID   string `json:"account_id,omitempty"`
}

const (
	commentLimit = 200

	commentExpand = "body.storage,version,history,history.createdBy," +
		"extensions.location,extensions.inlineProperties,extensions.resolution," +
		"children.comment.body.storage,children.comment.version,children.comment.history,children.comment.history.createdBy," +
		"children.comment.extensions.location,children.comment.extensions.inlineProperties,children.comment.extensions.resolution," +
		"children.comment.children.comment.body.storage,children.comment.children.comment.version," +
		"children.comment.children.comment.history,children.comment.children.comment.history.createdBy," +
		"children.comment.children.comment.extensions.location," +
		"children.comment.children.comment.extensions.inlineProperties," +
		"children.comment.children.comment.extensions.resolution"
)

type apiCommentList struct {
	Results []apiComment `json:"results"`
	Size    int          `json:"size"`
	Limit   int          `json:"limit"`
	Start   int          `json:"start"`
	Links   apiLinks     `json:"_links"`
}

type apiLinks struct {
	Next    string `json:"next"`
	Base    string `json:"base"`
	Context string `json:"context"`
}

type apiComment struct {
	ID         string         `json:"id"`
	Type       string         `json:"type"`
	Status     string         `json:"status"`
	Title      string         `json:"title"`
	Body       Body           `json:"body"`
	Version    apiVersionMeta `json:"version"`
	History    apiHistory     `json:"history"`
	Extensions apiExtensions  `json:"extensions"`
	Children   apiChildren    `json:"children"`
}

type apiVersionMeta struct {
	Number int       `json:"number"`
	When   time.Time `json:"when"`
	By     apiUser   `json:"by"`
}

type apiHistory struct {
	CreatedDate time.Time `json:"createdDate"`
	CreatedBy   apiUser   `json:"createdBy"`
}

type apiUser struct {
	Username    string `json:"username"`
	DisplayName string `json:"displayName"`
	UserKey     string `json:"userKey"`
	AccountID   string `json:"accountId"`
}

type apiExtensions struct {
	Location         string              `json:"location"`
	InlineProperties apiInlineProperties `json:"inlineProperties"`
	Resolution       apiResolution       `json:"resolution"`
}

type apiInlineProperties struct {
	MarkerRef         string `json:"markerRef"`
	OriginalSelection string `json:"originalSelection,omitempty"`
}

type apiResolution struct {
	Status       string    `json:"status"`
	LastModifier apiUser   `json:"lastModifier"`
	LastModified time.Time `json:"lastModified"`
}

type apiChildren struct {
	Comment apiCommentList `json:"comment"`
}

// GetComments fetches all comments (inline + footer) for the given page,
// following pagination and converting nested reply trees.
func (c *Client) GetComments(pageID string) ([]*Comment, error) {
	params := url.Values{
		"depth":  {"all"},
		"limit":  {fmt.Sprintf("%d", commentLimit)},
		"expand": {commentExpand},
	}
	path := fmt.Sprintf("/rest/api/content/%s/child/comment?%s", pageID, params.Encode())

	var out []*Comment
	for path != "" {
		page, err := c.fetchCommentPage(path, pageID)
		if err != nil {
			return nil, err
		}
		for i := range page.Results {
			out = append(out, convertComment(&page.Results[i]))
		}
		path = c.nextLinkPath(page.Links.Next)
	}
	return out, nil
}

func (c *Client) fetchCommentPage(path, pageID string) (*apiCommentList, error) {
	req, err := c.newRequest(http.MethodGet, path)
	if err != nil {
		return nil, err
	}

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("fetching comments for page %s: %w", pageID, err)
	}
	defer resp.Body.Close()

	if err := checkResponse(resp); err != nil {
		return nil, err
	}

	var list apiCommentList
	if err := json.NewDecoder(resp.Body).Decode(&list); err != nil {
		return nil, fmt.Errorf("decoding comments response: %w", err)
	}
	return &list, nil
}

// nextLinkPath normalizes the _links.next value into a path the client can
// pass to newRequest. Confluence DC sometimes returns it as a relative path
// ("/rest/api/...") and sometimes prefixed with the base URL.
func (c *Client) nextLinkPath(next string) string {
	if next == "" {
		return ""
	}
	if strings.HasPrefix(next, c.BaseURL) {
		return strings.TrimPrefix(next, c.BaseURL)
	}
	return next
}

func convertComment(in *apiComment) *Comment {
	out := &Comment{
		ID:          in.ID,
		Title:       in.Title,
		Status:      in.Status,
		Location:    in.Extensions.Location,
		MarkerRef:   in.Extensions.InlineProperties.MarkerRef,
		Resolution:  in.Extensions.Resolution.Status,
		Resolved:    in.Extensions.Resolution.Status == "resolved",
		Author:      convertUser(in.History.CreatedBy),
		Created:     in.History.CreatedDate,
		Updated:     in.Version.When,
		BodyStorage: in.Body.Storage.Value,
	}
	for i := range in.Children.Comment.Results {
		out.Replies = append(out.Replies, convertComment(&in.Children.Comment.Results[i]))
	}
	return out
}

func convertUser(in apiUser) User {
	return User{
		Username:    in.Username,
		DisplayName: in.DisplayName,
		UserKey:     in.UserKey,
		AccountID:   in.AccountID,
	}
}