import { strFromU8, strToU8, unzipSync, zipSync } from "fflate";
import type { MediaType } from "@sttracker/plugin-sdk/types";
import { toCsv } from "@sttracker/plugin-sdk/csv";
import type { Db } from "@sttracker/db/db";
import { newId } from "@sttracker/db/ids";
import { fromJson, toJson } from "@sttracker/db/json";
import type { AttachmentEntity, EntryStatus, Visibility } from "@sttracker/db/schema";
import { MAX_ATTACHMENT_BYTES, mimeAllowed, normalizeMime, sha256Hex, writeAttachmentFile } from "./attachments.ts";
import { isUniqueViolation } from "./matching.ts";
import { ImportError } from "./errors.ts";
import { createWorkIn, findWorkByExternalIdsIn, type K, type Position } from "./works.ts";

export const EXPORT_FORMAT = "sttracker-export/v1";

// Export rows are loosely typed records: the zip is untrusted input on import.
// eslint-disable-next-line @typescript-eslint/no-explicit-any
type Rec = Record<string, any>;

const camel = (s: string) => s.replace(/_([a-z0-9])/g, (_, c: string) => c.toUpperCase());
const snake = (s: string) => s.replace(/[A-Z]/g, (c) => `_${c.toLowerCase()}`);

const JSON_COLS = {
  works: ["creators", "metadata", "position"],
  entries: ["tags", "custom_fields", "overrides", "field_sources"],
  engagements: ["progress", "custom_fields", "field_sources"],
  listens: ["mbids"],
  copies: ["custom_fields"],
  defs: ["options", "applies_to"],
  history: ["before", "after"],
} as const;

/** DB row -> camelCase export record, JSON columns parsed, `drop` columns removed. */
function out(row: Rec, jsonCols: readonly string[], drop: readonly string[] = []): Rec {
  const o: Rec = {};
  for (const [k, v] of Object.entries(row)) {
    if (drop.includes(k)) continue;
    o[camel(k)] = jsonCols.includes(k) ? fromJson(v as string, null) : v;
  }
  return o;
}

/** camelCase export record -> snake_case row, JSON columns serialised. */
function inn(rec: Rec, jsonCols: readonly string[]): Rec {
  const o: Rec = {};
  for (const [k, v] of Object.entries(rec)) {
    const col = snake(k);
    o[col] = jsonCols.includes(col) ? toJson(v) : v;
  }
  return o;
}

const jsonl = (rows: Rec[]) => strToU8(rows.map((r) => JSON.stringify(r) + "\n").join(""));

function readJsonl(files: Record<string, Uint8Array>, name: string): Rec[] {
  const f = files[name];
  if (!f) return [];
  return strFromU8(f)
    .split("\n")
    .filter((l) => l.trim() !== "")
    .map((l) => JSON.parse(l) as Rec);
}

const CHUNK = 500;
const MAX_UNCOMPRESSED = 2 * 1024 * 1024 * 1024;

/** Run `fn` over `ids` in batches (keeps `IN (...)` lists under driver parameter limits). */
async function inChunks<T>(ids: readonly string[], fn: (chunk: string[]) => Promise<T[]>): Promise<T[]> {
  const all: T[] = [];
  for (let i = 0; i < ids.length; i += CHUNK) all.push(...(await fn(ids.slice(i, i + CHUNK))));
  return all;
}

/**
 * Per-user export bundle (zip). Includes soft-deleted rows so a restore is lossless; never credentials.
 * All reads happen in one transaction (repeatable read on Postgres) so the bundle is a consistent snapshot.
 */
export function exportUserBundle(db: Db, dataDir: string, userId: string): Promise<Uint8Array> {
  const tb = db.k.transaction();
  return (db.dialect === "postgres" ? tb.setIsolationLevel("repeatable read") : tb).execute((tx) => buildBundle(tx, dataDir, userId));
}

async function buildBundle(k: K, dataDir: string, userId: string): Promise<Uint8Array> {
  const user = await k.selectFrom("users").select(["username", "display_name"]).where("id", "=", userId).executeTakeFirstOrThrow();

  const entries = await k.selectFrom("entries").selectAll().where("user_id", "=", userId).orderBy("id").execute();
  const engagements = (
    await k.selectFrom("engagements").innerJoin("entries", "entries.id", "engagements.entry_id").selectAll("engagements").where("entries.user_id", "=", userId).orderBy("engagements.id").execute()
  );
  const listens = await k.selectFrom("listens").selectAll().where("user_id", "=", userId).orderBy("id").execute();
  const lists = await k.selectFrom("lists").selectAll().where("user_id", "=", userId).orderBy("id").execute();
  const items = await inChunks(lists.map((l) => l.id), (c) =>
    k.selectFrom("list_items").selectAll().where("list_id", "in", c).orderBy("position").orderBy("id").execute(),
  );
  const copies = await k.selectFrom("copies").selectAll().where("user_id", "=", userId).orderBy("id").execute();
  const defs = await k.selectFrom("custom_field_definitions").selectAll().where("user_id", "=", userId).orderBy("id").execute();
  const history = await k.selectFrom("user_history").selectAll().where("user_id", "=", userId).orderBy("created_at").orderBy("id").execute();
  const atts = await k.selectFrom("attachments").selectAll().where("user_id", "=", userId).orderBy("id").execute();
  const links = await inChunks(atts.map((a) => a.id), (c) => k.selectFrom("attachment_links").selectAll().where("attachment_id", "in", c).execute());
  const aliases = await k.selectFrom("work_aliases").selectAll().where("user_id", "=", userId).orderBy("id").execute();

  // Works: everything referenced, plus ancestors.
  const workIds = new Set<string>();
  for (const e of entries) workIds.add(e.work_id);
  for (const i of items) workIds.add(i.work_id);
  for (const c of copies) if (c.work_id) workIds.add(c.work_id);
  for (const l of listens) if (l.work_id) workIds.add(l.work_id);
  for (const a of aliases) {
    workIds.add(a.from_work_id);
    workIds.add(a.to_work_id);
  }
  const works = new Map<string, Rec>();
  let frontier = [...workIds];
  while (frontier.length) {
    const rows = await inChunks(frontier, (c) => k.selectFrom("works").selectAll().where("id", "in", c).execute());
    frontier = [];
    for (const w of rows) {
      works.set(w.id, w as Rec);
      // Ancestors and merge survivors are part of the bundle too.
      for (const ref of [w.parent_id, w.merged_into_id]) if (ref && !works.has(ref)) frontier.push(ref);
    }
  }
  const extIds = await inChunks([...works.keys()], (c) => k.selectFrom("external_ids").selectAll().where("work_id", "in", c).orderBy("namespace").execute());
  const extByWork = new Map<string, Record<string, string>>();
  for (const x of extIds) {
    const m = extByWork.get(x.work_id) ?? {};
    m[x.namespace] = x.value;
    extByWork.set(x.work_id, m);
  }
  const workRecs = [...works.values()]
    .sort((a, b) => (a.id < b.id ? -1 : 1))
    .map((w) => ({
      ...out(w, JSON_COLS.works, ["owner_user_id", "cover_attachment_id"]),
      private: w.owner_user_id != null,
      externalIds: extByWork.get(w.id) ?? {},
    }));

  const files: Record<string, Uint8Array> = {};
  const attRecs: Rec[] = [];
  for (const a of atts) {
    const file = Bun.file(`${dataDir}/attachments/${a.sha256.slice(0, 2)}/${a.sha256.slice(2, 4)}/${a.sha256}`);
    if (!(await file.exists())) continue;
    files[`attachments/${a.sha256}`] = new Uint8Array(await file.arrayBuffer());
    attRecs.push({
      ...out(a, [], ["user_id"]),
      links: links.filter((l) => l.attachment_id === a.id).map((l) => ({ entity: l.entity, entityId: l.entity_id })),
    });
  }

  const listRecs = lists.map((l) => ({
    ...out(l, [], ["user_id"]),
    items: items.filter((i) => i.list_id === l.id).map((i) => out(i, [], ["list_id"])),
  }));

  const manifest = {
    format: EXPORT_FORMAT,
    exportedAt: new Date().toISOString(),
    user: { username: user.username, displayName: user.display_name },
  };
  return zipSync({
    "manifest.json": strToU8(JSON.stringify(manifest, null, 2)),
    "works.jsonl": jsonl(workRecs),
    "entries.jsonl": jsonl(entries.map((e) => ({ ...out(e, JSON_COLS.entries, ["user_id"]), favorite: e.favorite !== 0 }))),
    "engagements.jsonl": jsonl(engagements.map((e) => out(e, JSON_COLS.engagements))),
    "listens.jsonl": jsonl(listens.map((l) => out(l, JSON_COLS.listens, ["user_id"]))),
    "lists.jsonl": jsonl(listRecs),
    "copies.jsonl": jsonl(copies.map((c) => out(c, JSON_COLS.copies, ["user_id"]))),
    "custom_fields.jsonl": jsonl(defs.map((d) => out(d, JSON_COLS.defs, ["user_id"]))),
    "work_aliases.jsonl": jsonl(aliases.map((a) => ({ fromWorkId: a.from_work_id, toWorkId: a.to_work_id }))),
    "history.jsonl": jsonl(history.map((h) => out(h, JSON_COLS.history, ["user_id"]))),
    "attachments.jsonl": jsonl(attRecs),
    ...files,
  });
}

/** CSV per entity type (live rows only): entries, engagements, listens. */
export async function exportUserCsv(db: Db, userId: string): Promise<Record<string, string>> {
  const k = db.k;
  const s = (v: unknown) => (v == null ? "" : String(v));
  const entries = await k
    .selectFrom("entries")
    .innerJoin("works", "works.id", "entries.work_id")
    .select(["entries.id", "entries.work_id", "works.title", "works.media_type", "works.year", "entries.status", "entries.rating", "entries.favorite", "entries.tags", "entries.review", "entries.created_at", "entries.updated_at"])
    .where("entries.user_id", "=", userId)
    .where("entries.deleted_at", "is", null)
    .orderBy("entries.id")
    .execute();
  const engagements = await k
    .selectFrom("engagements")
    .innerJoin("entries", "entries.id", "engagements.entry_id")
    .innerJoin("works", "works.id", "entries.work_id")
    .select(["engagements.id", "engagements.entry_id", "works.title", "engagements.started_at", "engagements.started_precision", "engagements.finished_at", "engagements.finished_precision", "engagements.platform", "engagements.rating", "engagements.notes"])
    .where("entries.user_id", "=", userId)
    .where("entries.deleted_at", "is", null)
    .where("engagements.deleted_at", "is", null)
    .orderBy("engagements.id")
    .execute();
  const listens = await k.selectFrom("listens").selectAll().where("user_id", "=", userId).orderBy("listened_at").orderBy("id").execute();

  return {
    "entries.csv": toCsv([
      ["id", "workId", "title", "mediaType", "year", "status", "rating", "favorite", "tags", "review", "createdAt", "updatedAt"],
      ...entries.map((e) => [e.id, e.work_id, e.title, e.media_type, s(e.year), e.status, s(e.rating), e.favorite ? "true" : "false", fromJson<string[]>(e.tags, []).join("; "), s(e.review), e.created_at, e.updated_at]),
    ]),
    "engagements.csv": toCsv([
      ["id", "entryId", "title", "startedAt", "startedPrecision", "finishedAt", "finishedPrecision", "platform", "rating", "notes"],
      ...engagements.map((e) => [e.id, e.entry_id, e.title, s(e.started_at), e.started_precision, s(e.finished_at), e.finished_precision, s(e.platform), s(e.rating), s(e.notes)]),
    ]),
    "listens.csv": toCsv([
      ["id", "listenedAt", "artist", "track", "album", "durationMs", "source"],
      ...listens.map((l) => [l.id, l.listened_at, l.artist, l.track, s(l.album), s(l.duration_ms), l.source]),
    ]),
  };
}

const UUID_RE = /[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/g;
const STATUSES: readonly EntryStatus[] = ["planned", "in_progress", "paused", "completed", "dropped", "none"];
const VISIBILITIES: readonly Visibility[] = ["private", "friends", "public"];

function corrupt(): never {
  throw new ImportError("corrupt_bundle");
}

function checkRatingValue(v: unknown): void {
  if (v != null && !(typeof v === "number" && Number.isInteger(v) && v >= 0 && v <= 100)) corrupt();
}

function checkRows(rows: Rec[], opts: { status?: boolean; visibility?: boolean; rating?: boolean }): void {
  for (const r of rows) {
    if (opts.rating) checkRatingValue(r.rating);
    if (opts.status && !STATUSES.includes(r.status)) corrupt();
    if (opts.visibility && !VISIBILITIES.includes(r.visibility)) corrupt();
  }
}

/**
 * Restore a bundle into an account with no entries. Works are re-matched by external id. Everything is
 * validated before anything is written; rows (attachments included) are inserted in one transaction.
 */
export async function importUserBundle(
  db: Db,
  dataDir: string,
  userId: string,
  zip: Uint8Array,
): Promise<{ works: number; entries: number }> {
  let files: Record<string, Uint8Array>;
  let total = 0;
  try {
    files = unzipSync(zip, {
      filter: (f) => {
        total += f.originalSize;
        if (total > MAX_UNCOMPRESSED) throw new ImportError("bundle_too_large");
        return true;
      },
    });
  } catch (e) {
    if (e instanceof ImportError) throw e;
    throw new ImportError("unsupported_format");
  }
  const mf = files["manifest.json"];
  let manifest: Rec = {};
  try {
    manifest = mf ? (JSON.parse(strFromU8(mf)) as Rec) : {};
  } catch {
    /* handled below */
  }
  if (manifest.format !== EXPORT_FORMAT) throw new ImportError("unsupported_format");

  const existing = await db.k.selectFrom("entries").select("id").where("user_id", "=", userId).limit(1).executeTakeFirst();
  if (existing) throw new ImportError("account_not_empty");

  let works: Rec[], entries: Rec[], engagements: Rec[], listens: Rec[], lists: Rec[], copies: Rec[];
  let defs: Rec[], history: Rec[], atts: Rec[], aliases: Rec[];
  try {
    works = readJsonl(files, "works.jsonl");
    entries = readJsonl(files, "entries.jsonl");
    engagements = readJsonl(files, "engagements.jsonl");
    listens = readJsonl(files, "listens.jsonl");
    lists = readJsonl(files, "lists.jsonl");
    copies = readJsonl(files, "copies.jsonl");
    defs = readJsonl(files, "custom_fields.jsonl");
    history = readJsonl(files, "history.jsonl");
    atts = readJsonl(files, "attachments.jsonl");
    aliases = readJsonl(files, "work_aliases.jsonl");
  } catch {
    return corrupt();
  }
  checkRows(entries, { rating: true, status: true, visibility: true });
  checkRows(engagements, { rating: true });
  checkRows(lists, { rating: true, visibility: true });

  // Attachments: validate everything before writing anything.
  for (const a of atts) {
    const bytes = files[`attachments/${a.sha256}`];
    if (
      !bytes ||
      !mimeAllowed(normalizeMime(String(a.mime ?? ""))) ||
      bytes.byteLength > MAX_ATTACHMENT_BYTES ||
      sha256Hex(bytes) !== a.sha256
    ) {
      throw new ImportError("invalid_attachment");
    }
  }
  for (const a of atts) await writeAttachmentFile(dataDir, files[`attachments/${a.sha256}`]!);

  const ids = new Map<string, string>();
  const remap = (old: unknown): string | null => (typeof old === "string" ? (ids.get(old) ?? null) : null);
  const remapCustom = (v: unknown): Rec => {
    const o: Rec = {};
    for (const [key, val] of Object.entries((v ?? {}) as Rec)) o[ids.get(key) ?? key] = val;
    return o;
  };

  // Parents before children.
  const byId = new Map(works.map((w) => [w.id as string, w]));
  const depth = (w: Rec): number => {
    let d = 0;
    const seen = new Set<string>();
    for (let p = w.parentId ? byId.get(w.parentId) : undefined; p && !seen.has(p.id); p = p.parentId ? byId.get(p.parentId) : undefined) {
      seen.add(p.id);
      d++;
    }
    return d;
  };
  const ordered = works.map((w) => ({ w, d: depth(w) })).sort((a, b) => a.d - b.d).map((x) => x.w);

  try {
    await db.k.transaction().execute(async (tx) => {
      const created = new Set<string>();
      for (const w of ordered) {
        const externalIds = (w.externalIds ?? {}) as Record<string, string>;
        const hasExt = Object.keys(externalIds).length > 0;
        const matched = hasExt ? await findWorkByExternalIdsIn(tx, externalIds, userId) : null;
        if (matched) {
          ids.set(w.id, matched);
          continue;
        }
        const newWorkId = await createWorkIn(
          tx,
          {
            hint: {
              title: w.title,
              mediaType: w.mediaType as MediaType,
              year: w.year ?? undefined,
              creators: w.creators ?? [],
              externalIds,
              coverUrl: w.coverUrl ?? "",
              description: w.description ?? "",
              position: (w.position ?? undefined) as Position | undefined,
            },
            ownerUserId: hasExt ? null : userId,
            parentId: remap(w.parentId),
          },
          "import",
        );
        await tx
          .updateTable("works")
          .set({
            original_title: w.originalTitle ?? "",
            release_date: w.releaseDate ?? null,
            metadata: toJson(w.metadata ?? {}),
            created_at: w.createdAt,
            updated_at: w.updatedAt,
          })
          .where("id", "=", newWorkId)
          .execute();
        ids.set(w.id, newWorkId);
        created.add(w.id);
      }

      // Tombstones: only for works created here (a matched existing work keeps its own state).
      for (const w of works) {
        const target = remap(w.mergedIntoId);
        if (!created.has(w.id) || !target) continue;
        await tx.updateTable("works").set({ merged_into_id: target }).where("id", "=", ids.get(w.id)!).execute();
      }
      for (const a of aliases) {
        const from = remap(a.fromWorkId);
        const to = remap(a.toWorkId);
        if (!from || !to || from === to) continue;
        await tx.insertInto("work_aliases").values({ id: newId(), user_id: userId, from_work_id: from, to_work_id: to }).execute();
      }

      for (const d of defs) {
        const id = newId();
        ids.set(d.id, id);
        await tx.insertInto("custom_field_definitions").values({ ...inn(d, JSON_COLS.defs), id, user_id: userId } as never).execute();
      }

      for (const e of entries) {
        const id = newId();
        ids.set(e.id, id);
        const workId = remap(e.workId);
        if (!workId) corrupt();
        await tx
          .insertInto("entries")
          .values({ ...inn(e, JSON_COLS.entries), id, user_id: userId, work_id: workId, favorite: e.favorite ? 1 : 0, custom_fields: toJson(remapCustom(e.customFields)) } as never)
          .execute();
      }

      for (const g of engagements) {
        const id = newId();
        ids.set(g.id, id);
        const entryId = remap(g.entryId);
        if (!entryId) corrupt();
        await tx
          .insertInto("engagements")
          .values({ ...inn(g, JSON_COLS.engagements), id, entry_id: entryId, custom_fields: toJson(remapCustom(g.customFields)) } as never)
          .execute();
      }

      for (const l of listens) {
        await tx
          .insertInto("listens")
          .values({ ...inn(l, JSON_COLS.listens), id: newId(), user_id: userId, work_id: remap(l.workId) } as never)
          .onConflict((oc) => oc.doNothing())
          .execute();
      }

      for (const l of lists) {
        const id = newId();
        ids.set(l.id, id);
        const { items, ...rest } = l;
        await tx.insertInto("lists").values({ ...inn(rest, []), id, user_id: userId } as never).execute();
        for (const it of (items ?? []) as Rec[]) {
          const workId = remap(it.workId);
          if (!workId) continue;
          await tx.insertInto("list_items").values({ ...inn(it, []), id: newId(), list_id: id, work_id: workId } as never).execute();
        }
      }

      for (const c of copies) {
        const id = newId();
        ids.set(c.id, id);
        await tx
          .insertInto("copies")
          .values({ ...inn(c, JSON_COLS.copies), id, user_id: userId, work_id: remap(c.workId), custom_fields: toJson(remapCustom(c.customFields)) } as never)
          .execute();
      }

      for (const a of atts) {
        const links = ((a.links ?? []) as Rec[])
          .map((l) => ({ entity: l.entity as AttachmentEntity, entityId: remap(l.entityId) }))
          .filter((l): l is { entity: AttachmentEntity; entityId: string } => l.entityId != null);
        if (links.length === 0) continue;
        const id = newId();
        const { links: _links, ...attRow } = a;
        await tx
          .insertInto("attachments")
          .values({ ...inn(attRow, []), id, user_id: userId, mime: normalizeMime(a.mime), size: files[`attachments/${a.sha256}`]!.byteLength } as never)
          .execute();
        for (const l of links) {
          await tx.insertInto("attachment_links").values({ id: newId(), attachment_id: id, entity: l.entity, entity_id: l.entityId }).execute();
        }
      }

      // History last, so every referenced id has been remapped.
      for (const h of history) {
        const sub = (v: unknown) => toJson(JSON.parse(JSON.stringify(v).replace(UUID_RE, (m) => ids.get(m) ?? m)));
        await tx
          .insertInto("user_history")
          .values({ ...inn(h, []), id: newId(), user_id: userId, entity_id: remap(h.entityId) ?? h.entityId, before: sub(h.before), after: sub(h.after) } as never)
          .execute();
      }
    });
  } catch (e) {
    if (e instanceof ImportError) throw e;
    if (isUniqueViolation(e)) throw new ImportError("conflict");
    throw e;
  }
  // An unlink of identical bytes between the pre-write and the commit may have removed a file.
  for (const a of atts) await writeAttachmentFile(dataDir, files[`attachments/${a.sha256}`]!);

  return { works: works.length, entries: entries.length };
}