CommandSuggester.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Octopus.CommandLine.Commands;
using Octopus.CommandLine.Extensions;

namespace Octopus.CommandLine.ShellCompletion;

public static class CommandSuggester
{
    public static IEnumerable<string> SuggestCommandsFor(
        string[] words,
        IReadOnlyDictionary<string, string[]> completionItems)
    {
        var executablePath = AssemblyHelper.GetExecutablePath();
        var exeName = Path.GetFileNameWithoutExtension(executablePath);
        var exeNameWithoutExtension = Path.GetFileNameWithoutExtension(executablePath);
        // some shells will pass the command name as invoked on the command line.
        // If so, strip them from the beginning of the array
        words = words
            .Take(2)
            .Except(new[] { exeName, exeNameWithoutExtension, CompleteCommand.Name }, StringComparer.OrdinalIgnoreCase)
            .Union(words.Skip(2))
            .Where(word => !string.IsNullOrWhiteSpace(word))
            .ToArray();

        var numberOfArgs = words.Length;
        var hasSubCommand = numberOfArgs > 1;
        var searchTerm =
            numberOfArgs > 0
                ? words.Last()
                : "";
        var suggestions = new List<string>();
        var isOptionSearch = searchTerm.StartsWith("--");
        var allSubCommands = completionItems.Keys.ToList();

        if (isOptionSearch)
        {
            if (hasSubCommand)
            {
                // e.g. `octo subcommand --searchTerm`
                var subCommandName = words.Where(w => IsSubCommand(w, allSubCommands)).Last();
                suggestions.AddRange(GetSubCommandOptionSuggestions(completionItems, subCommandName, searchTerm));
            }
            else
            {
                // e.g. `exename --searchTerm`
                return GetBaseOptionSuggestions(completionItems, searchTerm).OrderBy(name => name);
            }
        }
        else if (ZeroOrOneSubCommands(words, allSubCommands))
        {
            // e.g. `exename searchterm` or just `exename`
            suggestions.AddRange(GetSubCommandSuggestions(completionItems, searchTerm));
        }

        return suggestions.OrderBy(name => name);
    }

    static IEnumerable<string> GetSubCommandSuggestions(IReadOnlyDictionary<string, string[]> completionItems, string searchTerm)
    {
        return completionItems.Keys.Where(s =>
            s.StartsWith(searchTerm, StringComparison.OrdinalIgnoreCase));
    }

    static bool ZeroOrOneSubCommands(string[] words, List<string> allSubCommands)
    {
        return words.Where(w => IsSubCommand(w, allSubCommands)).Count() <= 1;
    }

    static IEnumerable<string> GetSubCommandOptionSuggestions(IReadOnlyDictionary<string, string[]> completionItems, string subCommandName, string searchTerm)
    {
        if (completionItems.TryGetValue(subCommandName, out var options))
            return options
                .Where(name => name.StartsWith(searchTerm, StringComparison.OrdinalIgnoreCase))
                .ToList();

        return new string[] { };
    }

    static IEnumerable<string> GetBaseOptionSuggestions(IReadOnlyDictionary<string, string[]> completionItems, string searchTerm)
        // If you type 'exename', you'll be redirected to the 'help' command, so show these options
        => GetSubCommandOptionSuggestions(completionItems, "help", searchTerm);

    static bool IsSubCommand(string arg, List<string> subCommandList)
    {
        if (arg == null) return false;
        if (arg.StartsWith("--")) return false;
        return subCommandList.Contains(arg);
    }
}