package hnblogs

import (
	"encoding/json"
	"fmt"
	"math/rand"
	"net/http"
	"sync"
)

const BlogsURL = "https://raw.githubusercontent.com/surprisetalk/blogs.hn/main/blogs.json"

// Blog represents a single blog entry.
type Blog struct {
	URL   string `json:"url"`
	Title string `json:"title"`
	About string `json:"about"`
	Now   string `json:"now"`
	Feed  string `json:"feed"`
	Desc  string `json:"desc"`
}

var (
	blogs       []Blog
	fetchError  error
	once        sync.Once
)

// FetchBlogs fetches the list of blogs and memoizes it in RAM.
func FetchBlogs() ([]Blog, error) {
	once.Do(func() {
		resp, err := http.Get(BlogsURL)
		if err != nil {
			fetchError = fmt.Errorf("failed to fetch blogs: %v", err)
			return
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			fetchError = fmt.Errorf("failed to fetch blogs: status code %d", resp.StatusCode)
			return
		}

		var fetchedBlogs []Blog
		if err := json.NewDecoder(resp.Body).Decode(&fetchedBlogs); err != nil {
			fetchError = fmt.Errorf("failed to decode blogs JSON: %v", err)
			return
		}

		blogs = fetchedBlogs
	})

	return blogs, fetchError
}

// GetBlogs returns the memoized list of blogs.
func GetBlogs() ([]Blog, error) {
	return FetchBlogs()
}

// RandomBlog returns a random blog from the list of blogs.
func RandomBlog() (Blog, error) {
	blogs, err := GetBlogs()
	if err != nil {
		return Blog{}, err
	}

	return blogs[rand.Intn(len(blogs))], nil
}

// RandomBlogs returns n random blogs from the list of blogs.
func RandomBlogs(n int) ([]Blog, error) {
	blogs, err := GetBlogs()
	if err != nil {
		return nil, err
	}

	if n <= 0 || n > len(blogs) {
		return nil, fmt.Errorf("invalid number of blogs requested")
	}

	selected := make([]Blog, n)
	for i := range selected {
		selected[i] = blogs[rand.Intn(len(blogs))]
	}

	return selected, nil
}

// NthBlog returns the nth blog from the list of blogs.
func NthBlog(n int) (Blog, error) {
	blogs, err := GetBlogs()
	if err != nil {
		return Blog{}, err
	}

	if n < 0 || n >= len(blogs) {
		return Blog{}, fmt.Errorf("index out of range")
	}

	return blogs[n], nil
}