import * as vscode from 'vscode';

// This ends up as the `type` key in tasks.json. RLS also uses `cargo` and
// our configuration should be compatible with it so use the same key.
const TASK_TYPE = 'cargo';

interface CargoTaskDefinition extends vscode.TaskDefinition {
    command?: string;
    args?: string[];
    cwd?: string;
    env?: { [key: string]: string };
}

class CargoTaskProvider implements vscode.TaskProvider {
    private readonly target: vscode.WorkspaceFolder;

    constructor(target: vscode.WorkspaceFolder) {
        this.target = target;
    }

    provideTasks(): vscode.Task[] {
        // Detect Rust tasks. Currently we do not do any actual detection
        // of tasks (e.g. aliases in .cargo/config) and just return a fixed
        // set of tasks that always exist. These tasks cannot be removed in
        // tasks.json - only tweaked.

        return [
            { command: 'build', group: vscode.TaskGroup.Build },
            { command: 'check', group: vscode.TaskGroup.Build },
            { command: 'test', group: vscode.TaskGroup.Test },
            { command: 'clean', group: vscode.TaskGroup.Clean },
            { command: 'run', group: undefined },
        ]
            .map(({ command, group }) => {
                const vscodeTask = new vscode.Task(
                    // The contents of this object end up in the tasks.json entries.
                    {
                        type: TASK_TYPE,
                        command,
                    },
                    // The scope of the task - workspace or specific folder (global
                    // is not supported).
                    this.target,
                    // The task name, and task source. These are shown in the UI as
                    // `${source}: ${name}`, e.g. `rust: cargo build`.
                    `cargo ${command}`,
                    'rust',
                    // What to do when this command is executed.
                    new vscode.ShellExecution('cargo', [command]),
                    // Problem matchers.
                    ['$rustc'],
                );
                vscodeTask.group = group;
                return vscodeTask;
            });
    }

    resolveTask(task: vscode.Task): vscode.Task | undefined {
        // VSCode calls this for every cargo task in the user's tasks.json,
        // we need to inform VSCode how to execute that command by creating
        // a ShellExecution for it.

        const definition = task.definition as CargoTaskDefinition;

        if (definition.type === 'cargo' && definition.command) {
            const args = [definition.command].concat(definition.args ?? []);

            return new vscode.Task(
                definition,
                task.name,
                'rust',
                new vscode.ShellExecution('cargo', args, definition),
            );
        }

        return undefined;
    }
}

export function activateTaskProvider(target: vscode.WorkspaceFolder): vscode.Disposable {
    const provider = new CargoTaskProvider(target);
    return vscode.tasks.registerTaskProvider(TASK_TYPE, provider);
}