// 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();

}