import { TRPCError } from "@trpc/server";
import { desc, eq, or } from "drizzle-orm";
import matter from "gray-matter";
import { UTApi, UTFile } from "uploadthing/server";
import z from "zod";
import { isAdmin } from "~/app/actions";
import { env } from "~/env.js";
import { db } from "~/server/db";
import { blogPost } from "~/server/dbschema/schema";
import { publicProcedure, router } from "~/server/trpc";

const utapi = new UTApi({ token: env.UPLOADTHING_TOKEN });

const blogPostInput = z.object({
  slug: z.string().min(1),
  title: z.string().min(1),
  date: z.string().optional(),
  description: z.string().optional(),
  tags: z.array(z.string()).optional(),
  content: z.string(),
});

type BlogPostInput = z.infer<typeof blogPostInput>;

type UploadThingFile = Awaited<ReturnType<typeof utapi.listFiles>>["files"][number];

function cleanPrefix(): string {
  return env.BLOG_MDX_PREFIX.trim().replace(/^\/+|\/+$/g, "");
}

function blogFileName(slug: string): string {
  const prefix = cleanPrefix();
  return prefix ? `${prefix}-${slug}.mdx` : `${slug}.mdx`;
}

function blogCustomId(slug: string): string {
  const prefix = cleanPrefix();
  const id = crypto.randomUUID();
  return prefix ? `${prefix}:${slug}:${id}` : `${slug}:${id}`;
}

function optionalText(value: string | undefined): string | null {
  const trimmed = value?.trim();
  return trimmed ? trimmed : null;
}

function frontmatterText(value: unknown): string | null {
  if (value instanceof Date) return value.toISOString().slice(0, 10);
  return optionalText(typeof value === "string" ? value : undefined);
}

function normalizeTags(tags: unknown): string[] {
  const values = Array.isArray(tags)
    ? tags
    : typeof tags === "string"
      ? tags.split(",")
      : [];

  return Array.from(
    new Set(
      values
        .map((tag) => String(tag).trim())
        .filter(Boolean),
    ),
  );
}

function createMdxContent(input: BlogPostInput): string {
  const date = optionalText(input.date);
  const description = optionalText(input.description);
  const tags = normalizeTags(input.tags);
  const frontmatter: Record<string, unknown> = { slug: input.slug, title: input.title };
  if (date) frontmatter.date = date;
  if (description) frontmatter.description = description;
  if (tags.length > 0) frontmatter.tags = tags;
  return matter.stringify(input.content, frontmatter);
}

function summaryFromInput(input: BlogPostInput) {
  return {
    slug: input.slug,
    title: input.title,
    date: optionalText(input.date),
    description: optionalText(input.description),
    tags: normalizeTags(input.tags),
  };
}

async function assertAdmin() {
  const admin = await isAdmin();
  if (!admin) throw new TRPCError({ code: "FORBIDDEN", message: "Access denied" });
}

async function uploadMdx(input: BlogPostInput) {
  const mdxContent = createMdxContent(input);
  const customId = blogCustomId(input.slug);
  const file = new UTFile([mdxContent], blogFileName(input.slug), {
    customId,
    type: "text/plain",
  });
  const result = await utapi.uploadFiles(file);

  if (result.error) {
    throw new TRPCError({ code: "INTERNAL_SERVER_ERROR", message: result.error.message });
  }

  if (!result.data.ufsUrl) {
    throw new TRPCError({ code: "INTERNAL_SERVER_ERROR", message: "UploadThing did not return a file URL" });
  }

  return {
    fileKey: result.data.key,
    fileUrl: result.data.ufsUrl,
    fileName: result.data.name,
    customId: result.data.customId ?? customId,
  };
}

async function fetchMdx(fileUrl: string): Promise<string> {
  const res = await fetch(fileUrl, { next: { revalidate: 3600 } });
  if (!res.ok) throw new TRPCError({ code: "INTERNAL_SERVER_ERROR", message: "Failed to fetch MDX file" });
  return res.text();
}

function fileUrl(file: Pick<UploadThingFile, "key">): string {
  return `https://utfs.io/f/${file.key}`;
}

function slugFromFileName(name: string): string {
  const prefix = cleanPrefix();
  const withoutExtension = name.replace(/\.mdx?$/, "");
  if (prefix && withoutExtension.startsWith(`${prefix}-`)) return withoutExtension.slice(prefix.length + 1);
  if (prefix && withoutExtension.startsWith(`${prefix}/`)) return withoutExtension.slice(prefix.length + 1);
  return withoutExtension;
}

function slugFromCustomId(customId: string): string {
  const prefix = cleanPrefix();
  const value = prefix && customId.startsWith(`${prefix}:`)
    ? customId.slice(prefix.length + 1)
    : customId;
  return value.split(":")[0] ?? value;
}

function fileMatchesPrefix(file: Pick<UploadThingFile, "name">): boolean {
  if (!/\.mdx?$/.test(file.name)) return false;

  const prefix = cleanPrefix();
  if (!prefix) return true;

  return file.name.startsWith(`${prefix}-`) || file.name.startsWith(`${prefix}/`);
}

function metadataFromFile(file: UploadThingFile, raw: string) {
  const parsed = matter(raw);
  const fallbackSlug = file.customId ? slugFromCustomId(file.customId) : slugFromFileName(file.name);

  return {
    slug: String(parsed.data.slug ?? fallbackSlug),
    title: String(parsed.data.title ?? fallbackSlug),
    date: frontmatterText(parsed.data.date),
    description: frontmatterText(parsed.data.description),
    tags: normalizeTags(parsed.data.tags),
    fileKey: file.key,
    fileUrl: fileUrl(file),
    fileName: file.name,
    customId: file.customId ?? blogCustomId(fallbackSlug),
  };
}

async function listAllFiles(): Promise<readonly UploadThingFile[]> {
  const files: UploadThingFile[] = [];
  let offset = 0;
  const limit = 500;
  let hasMore = true;

  while (hasMore) {
    const page = await utapi.listFiles({ limit, offset });
    files.push(...page.files);
    hasMore = page.hasMore;
    offset += limit;
  }

  return files;
}

export const blogRouter = router({
  insert: publicProcedure
    .input(blogPostInput)
    .mutation(async ({ input }) => {
      await assertAdmin();

      const existing = await db.query.blogPost.findFirst({
        where(fields, operators) {
          return operators.eq(fields.slug, input.slug);
        },
      });
      if (existing) throw new TRPCError({ code: "CONFLICT", message: `Post "${input.slug}" already exists` });

      const uploaded = await uploadMdx(input);

      try {
        await db.insert(blogPost).values({
          slug: input.slug,
          title: input.title,
          date: optionalText(input.date),
          description: optionalText(input.description),
          tags: normalizeTags(input.tags),
          ...uploaded,
        });
        return [summaryFromInput(input)];
      } catch (error) {
        await utapi.deleteFiles(uploaded.fileKey);
        throw error;
      }
    }),

  update: publicProcedure
    .input(blogPostInput.extend({ originalSlug: z.string().min(1) }))
    .mutation(async ({ input }) => {
      await assertAdmin();

      const existing = await db.query.blogPost.findFirst({
        where(fields, operators) {
          return operators.eq(fields.slug, input.originalSlug);
        },
      });
      if (!existing) throw new TRPCError({ code: "NOT_FOUND", message: `Post "${input.originalSlug}" not found` });

      if (input.slug !== input.originalSlug) {
        const slugConflict = await db.query.blogPost.findFirst({
          where(fields, operators) {
            return operators.eq(fields.slug, input.slug);
          },
        });
        if (slugConflict) throw new TRPCError({ code: "CONFLICT", message: `Post "${input.slug}" already exists` });
      }

      const uploaded = await uploadMdx(input);

      try {
        await db.update(blogPost).set({
          slug: input.slug,
          title: input.title,
          date: optionalText(input.date),
          description: optionalText(input.description),
          tags: normalizeTags(input.tags),
          ...uploaded,
        }).where(eq(blogPost.id, existing.id));

        await utapi.deleteFiles(existing.fileKey);
        return [summaryFromInput(input)];
      } catch (error) {
        await utapi.deleteFiles(uploaded.fileKey);
        throw error;
      }
    }),

  delete: publicProcedure
    .input(z.object({ id: z.string() }))
    .mutation(async ({ input }) => {
      await assertAdmin();

      const post = await db.query.blogPost.findFirst({
        where(fields, operators) {
          return operators.eq(fields.slug, input.id);
        },
      });
      if (!post) throw new TRPCError({ code: "NOT_FOUND", message: `Post "${input.id}" not found` });

      await db.delete(blogPost).where(eq(blogPost.id, post.id));
      await utapi.deleteFiles(post.fileKey);
      return [];
    }),

  list: publicProcedure.query(async () => {
    return db.select({
      slug: blogPost.slug,
      title: blogPost.title,
      date: blogPost.date,
      description: blogPost.description,
      tags: blogPost.tags,
    }).from(blogPost).orderBy(desc(blogPost.date), desc(blogPost.createdAt));
  }),

  bySlug: publicProcedure.input(z.string()).query(async ({ input: slug }) => {
    const post = await db.query.blogPost.findFirst({
      where(fields, operators) {
        return operators.eq(fields.slug, slug);
      },
    });

    if (!post) throw new TRPCError({ code: "NOT_FOUND", message: `Post "${slug}" not found` });

    const raw = await fetchMdx(post.fileUrl);
    const { content, data } = matter(raw);

    return {
      slug: post.slug,
      content,
      title: (data.title as string | undefined) ?? post.title,
      date: frontmatterText(data.date) ?? post.date,
      description: frontmatterText(data.description) ?? post.description,
      tags: normalizeTags(data.tags).length > 0 ? normalizeTags(data.tags) : (post.tags ?? []),
    };
  }),

  syncFromUploadThing: publicProcedure.mutation(async () => {
    await assertAdmin();

    const files = (await listAllFiles()).filter(fileMatchesPrefix);
    const seenFileKeys = new Set<string>();
    const seenSlugs = new Set<string>();
    let created = 0;
    let updated = 0;
    let skipped = 0;
    let deleted = 0;

    for (const file of files) {
      try {
        const raw = await fetchMdx(fileUrl(file));
        const metadata = metadataFromFile(file, raw);
        seenFileKeys.add(file.key);
        seenSlugs.add(metadata.slug);
        const existing = await db.query.blogPost.findFirst({
          where(fields, operators) {
            return or(operators.eq(fields.fileKey, file.key), operators.eq(fields.slug, metadata.slug));
          },
        });

        if (existing) {
          await db.update(blogPost).set(metadata).where(eq(blogPost.id, existing.id));
          updated += 1;
        } else {
          await db.insert(blogPost).values(metadata);
          created += 1;
        }
      } catch {
        skipped += 1;
      }
    }

    const posts = await db.select({
      id: blogPost.id,
      fileKey: blogPost.fileKey,
      slug: blogPost.slug,
    }).from(blogPost);

    const stalePostIds = posts
      .filter((post) => !seenFileKeys.has(post.fileKey) && !seenSlugs.has(post.slug))
      .map((post) => post.id);

    for (const id of stalePostIds) {
      await db.delete(blogPost).where(eq(blogPost.id, id));
      deleted += 1;
    }

    return { created, updated, skipped, deleted };
  }),
});