// Copyright 2005-2015 Giacomo Stelluti Scala & Contributors. All rights reserved. See License.md in the project root for license information.

using CommandLine.Infrastructure;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CommandLine.Text
{
    /// <summary>
    /// Exposes standard delegates to provide a mean to customize part of help screen generation.
    /// This type is consumed by <see cref="CommandLine.Text.HelpText"/>.
    /// </summary>
    public abstract class SentenceBuilder
    {
        /// <summary>
        /// Create instance of <see cref="CommandLine.Text.SentenceBuilder"/>,
        /// </summary>
        /// <returns>The <see cref="CommandLine.Text.SentenceBuilder"/> instance.</returns>
        public static SentenceBuilder Create()
        {
            return Factory();
        }

        /// <summary>
        /// Factory to allow custom SentenceBuilder injection
        /// </summary>
        public static Func<SentenceBuilder> Factory { get; set; } = () => new DefaultSentenceBuilder();

        /// <summary>
        /// Gets a delegate that returns the word 'required'.
        /// </summary>
        public abstract Func<string> RequiredWord { get; }

        /// <summary>
        /// Gets a delegate that returns the word 'group'.
        /// </summary>
        public abstract Func<string> OptionGroupWord { get; }

        /// <summary>
        /// Gets a delegate that returns that errors block heading text.
        /// </summary>
        public abstract Func<string> ErrorsHeadingText { get; }

        /// <summary>
        /// Gets a delegate that returns usage text block heading text.
        /// </summary>
        public abstract Func<string> UsageHeadingText { get; }

        /// <summary>
        /// Get a delegate that returns the help text of help command.
        /// The delegates must accept a boolean that is equal <value>true</value> for options; otherwise <value>false</value> for verbs.
        /// </summary>
        public abstract Func<bool, string> HelpCommandText { get; }

        /// <summary>
        /// Get a delegate that returns the help text of vesion command.
        /// The delegates must accept a boolean that is equal <value>true</value> for options; otherwise <value>false</value> for verbs.
        /// </summary>
        public abstract Func<bool, string> VersionCommandText { get; }

        /// <summary>
        /// Gets a delegate that handles singular error formatting.
        /// The delegates must accept an <see cref="Error"/> and returns a string.
        /// </summary>
        public abstract Func<Error, string> FormatError { get; }

        /// <summary>
        /// Gets a delegate that handles mutually exclusive set errors formatting.
        /// The delegates must accept a sequence of <see cref="MutuallyExclusiveSetError"/> and returns a string.
        /// </summary>
        public abstract Func<IEnumerable<MutuallyExclusiveSetError>, string> FormatMutuallyExclusiveSetErrors { get; }

        private class DefaultSentenceBuilder : SentenceBuilder
        {
            public override Func<string> RequiredWord
            {
                get { return () => "Required."; }
            }

            public override Func<string> ErrorsHeadingText
            {
                get { return () => "ERROR(S):"; }
            }

            public override Func<string> UsageHeadingText
            {
                get { return () => "USAGE:"; }
            }

            public override Func<string> OptionGroupWord
            {
                get { return () => "Group"; }
            }

            public override Func<bool, string> HelpCommandText
            {
                get
                {
                    return isOption => isOption
                        ? "Display this help screen."
                        : "Display more information on a specific command.";
                }
            }

            public override Func<bool, string> VersionCommandText
            {
                get { return _ => "Display version information."; }
            }

            public override Func<Error, string> FormatError
            {
                get
                {
                    return error =>
                        {
                            switch (error.Tag)
                            {
                                case ErrorType.BadFormatTokenError:
                                    return "Token '".JoinTo(((BadFormatTokenError)error).Token, "' is not recognized.");
                                case ErrorType.MissingValueOptionError:
                                    return "Option '".JoinTo(((MissingValueOptionError)error).NameInfo.NameText,
                                        "' has no value.");
                                case ErrorType.UnknownOptionError:
                                    return "Option '".JoinTo(((UnknownOptionError)error).Token, "' is unknown.");
                                case ErrorType.MissingRequiredOptionError:
                                    var errMisssing = ((MissingRequiredOptionError)error);
                                    return errMisssing.NameInfo.Equals(NameInfo.EmptyName)
                                               ? "A required value not bound to option name is missing."
                                               : "Required option '".JoinTo(errMisssing.NameInfo.NameText, "' is missing.");
                                case ErrorType.BadFormatConversionError:
                                    var badFormat = ((BadFormatConversionError)error);
                                    return badFormat.NameInfo.Equals(NameInfo.EmptyName)
                                               ? "A value not bound to option name is defined with a bad format."
                                               : "Option '".JoinTo(badFormat.NameInfo.NameText, "' is defined with a bad format.");
                                case ErrorType.SequenceOutOfRangeError:
                                    var seqOutRange = ((SequenceOutOfRangeError)error);
                                    return seqOutRange.NameInfo.Equals(NameInfo.EmptyName)
                                               ? "A sequence value not bound to option name is defined with few items than required."
                                               : "A sequence option '".JoinTo(seqOutRange.NameInfo.NameText,
                                                    "' is defined with fewer or more items than required.");
                                case ErrorType.BadVerbSelectedError:
                                    return "Verb '".JoinTo(((BadVerbSelectedError)error).Token, "' is not recognized.");
                                case ErrorType.NoVerbSelectedError:
                                    return "No verb selected.";
                                case ErrorType.RepeatedOptionError:
                                    return "Option '".JoinTo(((RepeatedOptionError)error).NameInfo.NameText,
                                        "' is defined multiple times.");
                                case ErrorType.SetValueExceptionError:
                                    var setValueError = (SetValueExceptionError)error;
                                    return "Error setting value to option '".JoinTo(setValueError.NameInfo.NameText, "': ", setValueError.Exception.Message);
                                case ErrorType.MissingGroupOptionError:
                                    var missingGroupOptionError = (MissingGroupOptionError)error;
                                    return "At least one option from group '".JoinTo(
                                        missingGroupOptionError.Group,
                                        "' (",
                                        string.Join(", ", missingGroupOptionError.Names.Select(n => n.NameText)),
                                        ") is required.");
                                case ErrorType.GroupOptionAmbiguityError:
                                    var groupOptionAmbiguityError = (GroupOptionAmbiguityError)error;
                                    return "Both SetName and Group are not allowed in option: (".JoinTo(groupOptionAmbiguityError.Option.NameText, ")");
                                case ErrorType.MultipleDefaultVerbsError:
                                    return MultipleDefaultVerbsError.ErrorMessage;

                            }
                            throw new InvalidOperationException();
                        };
                }
            }

            public override Func<IEnumerable<MutuallyExclusiveSetError>, string> FormatMutuallyExclusiveSetErrors
            {
                get
                {
                    return errors =>
                    {
                        var bySet = from e in errors
                                    group e by e.SetName into g
                                    select new { SetName = g.Key, Errors = g.ToList() };

                        var msgs = bySet.Select(
                            set =>
                            {
                                var names = string.Join(
                                    string.Empty,
                                    (from e in set.Errors select "'".JoinTo(e.NameInfo.NameText, "', ")).ToArray());
                                var namesCount = set.Errors.Count();

                                var incompat = string.Join(
                                    string.Empty,
                                    (from x in
                                         (from s in bySet where !s.SetName.Equals(set.SetName) from e in s.Errors select e)
                                        .Distinct()
                                     select "'".JoinTo(x.NameInfo.NameText, "', ")).ToArray());

                                return
                                    new StringBuilder("Option")
                                            .AppendWhen(namesCount > 1, "s")
                                            .Append(": ")
                                            .Append(names.Substring(0, names.Length - 2))
                                            .Append(' ')
                                            .AppendIf(namesCount > 1, "are", "is")
                                            .Append(" not compatible with: ")
                                            .Append(incompat.Substring(0, incompat.Length - 2))
                                            .Append('.')
                                        .ToString();
                            }).ToArray();
                        return string.Join(Environment.NewLine, msgs);
                    };
                }
            }
        }
    }
}