import fs from "fs"
import path from "path"
import matter from "gray-matter"
import { remark } from "remark"
import html from "remark-html"

const postsDirectory = path.join(process.cwd(), "content/posts")

export interface PostMeta {
  slug: string
  title: string
  description: string
  author: string
  date: string
  categories: string[]
  tags: string[]
  math: boolean
  mermaid: boolean
}

export function getAllPostSlugs(): string[] {
  return fs
    .readdirSync(postsDirectory)
    .filter((f) => f.endsWith(".md"))
    .map((f) => f.replace(/\.md$/, ""))
}

export function getAllPostsMeta(): PostMeta[] {
  return getAllPostSlugs()
    .map((slug) => {
      const fullPath = path.join(postsDirectory, `${slug}.md`)
      const { data } = matter(fs.readFileSync(fullPath, "utf8"))
      return { slug, ...(data as Omit<PostMeta, "slug">) }
    })
    .sort((a, b) => (a.date < b.date ? 1 : -1))
}

export async function getPostBySlug(slug: string) {
  const fullPath = path.join(postsDirectory, `${slug}.md`)
  const { data, content } = matter(fs.readFileSync(fullPath, "utf8"))
  const processedHtml = await remark().use(html).process(content)

  return {
    meta: { slug, ...(data as Omit<PostMeta, "slug">) },
    contentHtml: processedHtml.toString(),
  }
}

export function getPostsByCategory(category: string): PostMeta[] {
  return getAllPostsMeta().filter((post) =>
    post.categories.includes(category),
  )
}

export function getPostsByTag(tag: string): PostMeta[] {
  return getAllPostsMeta().filter((post) => post.tags.includes(tag))
}