import * as vscode from 'vscode';
import { SyncApi } from './api';
import { LiveSpace } from './liveSpace';
import { Version, VersionFiles, versionLabel } from './protocol';

export const VERSION_SCHEME = 'archify-sync-version';

/** Read-only documents of a version's files: `archify-sync-version:/<space>/<version>/<path>`. */
export class VersionContent implements vscode.TextDocumentContentProvider {
  private readonly cache = new Map<string, Promise<VersionFiles>>();

  constructor(private readonly api: (space: string) => SyncApi | undefined) {}

  files(space: string, version: number): Promise<VersionFiles> {
    const key = `${space}/${version}`;
    let found = this.cache.get(key);
    if (!found) {
      const api = this.api(space);
      if (!api) return Promise.reject(new Error('This model is not shared from here.'));
      found = api.versionFiles(space, version);
      found.catch(() => this.cache.delete(key));
      this.cache.set(key, found);
    }
    return found;
  }

  async provideTextDocumentContent(uri: vscode.Uri): Promise<string> {
    const [, space, version, ...rest] = uri.path.split('/');
    const files = await this.files(space, Number(version));
    return files.files.find((f) => f.path === rest.join('/'))?.text ?? '';
  }
}

function describe(v: Version): vscode.QuickPickItem & { version: Version } {
  const when = new Date(v.created_at).toLocaleString();
  const kind = v.kind === 'publish' ? 'published' : v.kind === 'restore' ? `restored ${v.restored_from ?? ''}`.trim() : 'snapshot';
  return {
    label: `${v.kind === 'publish' ? '$(tag)' : v.kind === 'restore' ? '$(history)' : '$(circle-small)'} ${versionLabel(v)}${v.name ? `  ${v.name}` : ''}`,
    description: kind,
    detail: when,
    version: v,
  };
}

/** Versions of a space: pick one, then compare with the files here or restore it. */
export async function showVersions(space: LiveSpace, api: SyncApi, content: VersionContent): Promise<void> {
  const versions = await api.versions(space.link.space);
  if (!versions.length) {
    vscode.window.showInformationMessage(`Archify: ${space.name} has no versions yet. One is taken on its own after a pause in editing.`);
    return;
  }
  const picked = await vscode.window.showQuickPick(versions.map(describe), { title: `Archify | Versions of ${space.name}`, placeHolder: 'Pick a version' });
  if (!picked) return;
  const v = picked.version;
  const action = await vscode.window.showQuickPick(
    [
      { label: '$(diff) Compare with the files here', id: 'compare' },
      { label: '$(history) Restore this version', id: 'restore', detail: 'Brings these files back for everyone, as a new version. Nothing is lost.' },
    ],
    { title: `Archify | ${versionLabel(v)}${v.name ? ` ${v.name}` : ''}` },
  );
  if (action?.id === 'compare') await compareVersion(space, v, content);
  if (action?.id === 'restore') await restoreVersion(space, api, v);
}

/** Asks, then brings back a version's files for everyone as a new version. */
export async function restoreVersion(space: LiveSpace, api: SyncApi, v: Version): Promise<boolean> {
  const ok = await vscode.window.showWarningMessage(
    `Restore ${versionLabel(v)} of ${space.name} for everyone?`,
    { modal: true, detail: 'The files go back to this version for everyone in the space. It becomes a new version; the history stays.' },
    'Restore',
  );
  if (ok !== 'Restore') return false;
  const restored = await api.restore(space.link.space, v.id);
  vscode.window.showInformationMessage(`Archify: restored ${versionLabel(v)} as ${versionLabel(restored)}.`);
  return true;
}

/** Lists the files that differ from a version and opens the diff of the one picked. */
export async function compareVersion(space: LiveSpace, v: Version, content: VersionContent): Promise<void> {
  const files = await content.files(space.link.space, v.id);
  const here = new Map<string, string>();
  for (const [rel, text] of space.doc.getMap<{ toString(): string }>('files').entries()) here.set(rel, text.toString());
  const paths = [...new Set([...files.files.map((f) => f.path), ...here.keys()])].sort();
  const changed = paths
    .map((p) => ({ path: p, then: files.files.find((f) => f.path === p)?.text, now: here.get(p) }))
    .filter((f) => f.then !== f.now);
  if (!changed.length) {
    vscode.window.showInformationMessage(`Archify: the files here are the same as ${versionLabel(v)}.`);
    return;
  }
  const pick = await vscode.window.showQuickPick(
    changed.map((f) => ({ label: f.path, description: f.then === undefined ? 'added since' : f.now === undefined ? 'removed since' : 'changed', path: f.path })),
    { title: `Archify | Changes since ${versionLabel(v)}`, placeHolder: `${changed.length} file(s) differ` },
  );
  if (!pick) return;
  const left = vscode.Uri.from({ scheme: VERSION_SCHEME, path: `/${space.link.space}/${v.id}/${pick.path}` });
  const right = vscode.Uri.joinPath(space.root, ...pick.path.split('/'));
  await vscode.commands.executeCommand('vscode.diff', left, right, `${pick.path} (${versionLabel(v)} ↔ here)`);
}