package ntfy

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"

	"lazyntfy/internal/config"
)

type accountBody struct {
	SyncTopic     string `json:"sync_topic"`
	Subscriptions []struct {
		BaseURL     string  `json:"base_url"`
		Topic       string  `json:"topic"`
		DisplayName *string `json:"display_name"`
	} `json:"subscriptions"`
	Reservations []struct {
		Topic string `json:"topic"`
	} `json:"reservations"`
}

type grantBody struct {
	Topic      string `json:"topic"`
	Permission string `json:"permission"`
}

type userBody struct {
	Grants []grantBody `json:"grants"`
}

// AccountTopics lists topics visible to this login: account subscriptions,
// reserved topics, and ACL grants when the token can read /v1/users.
// Wildcard patterns are skipped. Credentials are not included in errors.
func (c *Client) AccountTopics(ctx context.Context, host string, auth config.Auth) ([]config.Sub, error) {
	host = strings.TrimRight(strings.TrimSpace(host), "/")
	if host == "" || (auth.Token == "" && auth.User == "") {
		return nil, nil
	}
	body, status, err := c.get(ctx, host+"/v1/account", auth)
	if err != nil {
		return nil, err
	}
	if status == http.StatusUnauthorized || status == http.StatusForbidden {
		return nil, fmt.Errorf("HTTP %d: not authorized to list topics", status)
	}
	if status < 200 || status >= 300 {
		return nil, fmt.Errorf("HTTP %d from /v1/account", status)
	}
	var account accountBody
	if err := json.Unmarshal(body, &account); err != nil {
		return nil, fmt.Errorf("account response: %w", err)
	}

	var subs []config.Sub
	seen := map[string]bool{}
	add := func(base, topic, display string) {
		topic = strings.TrimSpace(topic)
		if topic == "" || strings.Contains(topic, "*") || topic == account.SyncTopic {
			return
		}
		originHost := host
		if strings.TrimSpace(base) != "" {
			originHost = strings.TrimRight(base, "/")
		}
		origin, name, err := config.Resolve(topic, originHost)
		if err != nil {
			return
		}
		key := origin + "\n" + name
		if seen[key] {
			return
		}
		seen[key] = true
		subs = append(subs, config.Sub{
			Origin:  origin,
			Name:    name,
			Display: strings.TrimSpace(display),
			Auth:    auth,
		})
	}

	for _, sub := range account.Subscriptions {
		display := ""
		if sub.DisplayName != nil {
			display = *sub.DisplayName
		}
		add(sub.BaseURL, sub.Topic, display)
	}
	for _, res := range account.Reservations {
		add("", res.Topic, "")
	}

	usersBody, usersStatus, err := c.get(ctx, host+"/v1/users", auth)
	if err != nil || usersStatus < 200 || usersStatus >= 300 {
		return subs, nil
	}
	for _, grant := range parseGrants(usersBody) {
		perm := strings.ToLower(grant.Permission)
		if perm == "deny-all" || perm == "deny" || perm == "none" {
			continue
		}
		add("", grant.Topic, "")
	}
	return subs, nil
}

func parseGrants(body []byte) []grantBody {
	var wrapped struct {
		Users []userBody `json:"users"`
	}
	if err := json.Unmarshal(body, &wrapped); err == nil && wrapped.Users != nil {
		return flattenGrants(wrapped.Users)
	}
	var list []userBody
	if err := json.Unmarshal(body, &list); err != nil {
		return nil
	}
	return flattenGrants(list)
}

func flattenGrants(users []userBody) []grantBody {
	var out []grantBody
	for _, user := range users {
		out = append(out, user.Grants...)
	}
	return out
}

func (c *Client) get(ctx context.Context, endpoint string, auth config.Auth) ([]byte, int, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return nil, 0, err
	}
	req.Header.Set("User-Agent", userAgent)
	req.Header.Set("Accept", "application/json")
	auth.Apply(req)
	resp, err := c.http().Do(req)
	if err != nil {
		return nil, 0, err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return nil, resp.StatusCode, err
	}
	return body, resp.StatusCode, nil
}