// The operation log as a tree view (spec §5.9): newest first, with
// "Undo to here" on any entry, snapshots hidden unless configured.

import * as vscode from "vscode";
import { OperationInfo } from "./oxy";
import { Repository } from "./repository";

export class OperationItem extends vscode.TreeItem {
  constructor(
    readonly repository: Repository,
    readonly op: OperationInfo,
    readonly stepsBack: number,
  ) {
    super(op.command, vscode.TreeItemCollapsibleState.None);
    this.id = `${repository.root}:${op.id}`;
    this.description = timeAgo(op.when_ms);
    this.tooltip = `${op.command}\n${new Date(op.when_ms).toLocaleString()}\n${op.id.slice(0, 12)}`;
    this.iconPath = new vscode.ThemeIcon(op.current ? "circle-filled" : op.snapshot ? "circle-small" : "circle-outline");
    this.contextValue = op.current ? "current" : "operation";
  }
}

export class OperationsProvider implements vscode.TreeDataProvider<OperationItem | RepositoryItem> {
  private readonly emitter = new vscode.EventEmitter<void>();
  readonly onDidChangeTreeData = this.emitter.event;

  constructor(private readonly repositories: () => Repository[]) {}

  refresh(): void {
    this.emitter.fire();
  }

  getTreeItem(element: OperationItem | RepositoryItem): vscode.TreeItem {
    return element;
  }

  async getChildren(element?: OperationItem | RepositoryItem): Promise<(OperationItem | RepositoryItem)[]> {
    const repos = this.repositories();
    if (!element) {
      if (repos.length === 1) {
        return this.operations(repos[0]);
      }
      return repos.map((r) => new RepositoryItem(r));
    }
    if (element instanceof RepositoryItem) {
      return this.operations(element.repository);
    }
    return [];
  }

  private async operations(repo: Repository): Promise<OperationItem[]> {
    const showSnapshots = vscode.workspace.getConfiguration("oxygen").get<boolean>("showSnapshotOperations", false);
    try {
      const ops = await repo.oxy.opLog(repo.root);
      const items: OperationItem[] = [];
      // Steps back count every operation, snapshots included, since undo
      // skips snapshots itself only when they are the newest entries.
      let steps = 0;
      for (const op of ops) {
        if (showSnapshots || !op.snapshot || op.current) {
          items.push(new OperationItem(repo, op, steps));
        }
        if (!op.snapshot) {
          steps += 1;
        }
      }
      return items.slice(0, 200);
    } catch {
      return [];
    }
  }
}

export class RepositoryItem extends vscode.TreeItem {
  constructor(readonly repository: Repository) {
    super(repository.root.split("/").pop() ?? repository.root, vscode.TreeItemCollapsibleState.Expanded);
    this.iconPath = new vscode.ThemeIcon("repo");
    this.contextValue = "repository";
  }
}

export function timeAgo(ms: number): string {
  const s = Math.max(0, Math.round((Date.now() - ms) / 1000));
  if (s < 45) return "just now";
  if (s < 90) return "a minute ago";
  if (s < 2700) return `${Math.round(s / 60)} minutes ago`;
  if (s < 5400) return "an hour ago";
  if (s < 79200) return `${Math.round(s / 3600)} hours ago`;
  if (s < 129600) return "yesterday";
  if (s < 2592000) return `${Math.round(s / 86400)} days ago`;
  return new Date(ms).toLocaleDateString();
}