using System;
using StardewModdingAPI.Toolkit.Utilities;
using StardewValley;

namespace StardewModdingAPI.Framework.Content
{
    /// <summary>An asset name that can be loaded through the content pipeline.</summary>
    internal class AssetName : IAssetName
    {
        /*********
        ** Fields
        *********/
        /// <summary>A lowercase version of <see cref="Name"/> used for consistent hash codes and equality checks.</summary>
        private readonly string ComparableName;


        /*********
        ** Accessors
        *********/
        /// <inheritdoc />
        public string Name { get; }

        /// <inheritdoc />
        public string BaseName { get; }

        /// <inheritdoc />
        public string LocaleCode { get; }

        /// <inheritdoc />
        public LocalizedContentManager.LanguageCode? LanguageCode { get; }


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="baseName">The base asset name without the locale code.</param>
        /// <param name="localeCode">The locale code specified in the <see cref="Name"/>, if it's a valid code recognized by the game content.</param>
        /// <param name="languageCode">The language code matching the <see cref="LocaleCode"/>, if applicable.</param>
        public AssetName(string baseName, string localeCode, LocalizedContentManager.LanguageCode? languageCode)
        {
            // validate
            if (string.IsNullOrWhiteSpace(baseName))
                throw new ArgumentException("The asset name can't be null or empty.", nameof(baseName));
            if (string.IsNullOrWhiteSpace(localeCode))
                localeCode = null;

            // set base values
            this.BaseName = PathUtilities.NormalizeAssetName(baseName);
            this.LocaleCode = localeCode;
            this.LanguageCode = languageCode;

            // set derived values
            this.Name = localeCode != null
                ? string.Concat(this.BaseName, '.', this.LocaleCode)
                : this.BaseName;
            this.ComparableName = this.Name.ToLowerInvariant();
        }

        /// <summary>Parse a raw asset name into an instance.</summary>
        /// <param name="rawName">The raw asset name to parse.</param>
        /// <param name="parseLocale">Get the language code for a given locale, if it's valid.</param>
        /// <exception cref="ArgumentException">The <paramref name="rawName"/> is null or empty.</exception>
        public static AssetName Parse(string rawName, Func<string, LocalizedContentManager.LanguageCode?> parseLocale)
        {
            if (string.IsNullOrWhiteSpace(rawName))
                throw new ArgumentException("The asset name can't be null or empty.", nameof(rawName));

            string baseName = rawName;
            string localeCode = null;
            LocalizedContentManager.LanguageCode? languageCode = null;

            int lastPeriodIndex = rawName.LastIndexOf('.');
            if (lastPeriodIndex > 0 && rawName.Length > lastPeriodIndex + 1)
            {
                string possibleLocaleCode = rawName[(lastPeriodIndex + 1)..];
                LocalizedContentManager.LanguageCode? possibleLanguageCode = parseLocale(possibleLocaleCode);

                if (possibleLanguageCode != null)
                {
                    baseName = rawName[..lastPeriodIndex];
                    localeCode = possibleLocaleCode;
                    languageCode = possibleLanguageCode;
                }
            }

            return new AssetName(baseName, localeCode, languageCode);
        }

        /// <inheritdoc />
        public bool IsEquivalentTo(string assetName, bool useBaseName = false)
        {
            // empty asset key is never equivalent
            if (string.IsNullOrWhiteSpace(assetName))
                return false;

            assetName = PathUtilities.NormalizeAssetName(assetName);

            string compareTo = useBaseName ? this.BaseName : this.Name;
            return compareTo.Equals(assetName, StringComparison.OrdinalIgnoreCase);
        }

        /// <inheritdoc />
        public bool StartsWith(string prefix, bool allowPartialWord = true, bool allowSubfolder = true)
        {
            // asset keys never start with null
            if (prefix is null)
                return false;

            // asset keys can't have a leading slash, but NormalizeAssetName will trim them
            {
                string trimmed = prefix.TrimStart();
                if (trimmed.StartsWith('/') || trimmed.StartsWith('\\'))
                    return false;
            }

            // normalize prefix
            {
                string normalized = PathUtilities.NormalizeAssetName(prefix);

                string trimmed = prefix.TrimEnd();
                if (trimmed.EndsWith('/') || trimmed.EndsWith('\\'))
                    normalized += PathUtilities.PreferredAssetSeparator;

                prefix = normalized;
            }

            // compare
            return
                this.Name.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)
                && (
                    allowPartialWord
                    || this.Name.Length == prefix.Length
                    || !char.IsLetterOrDigit(prefix[^1]) // last character in suffix is word separator
                    || !char.IsLetterOrDigit(this.Name[prefix.Length]) // or first character after it is
                )
                && (
                    allowSubfolder
                    || this.Name.Length == prefix.Length
                    || !this.Name[prefix.Length..].Contains(PathUtilities.PreferredAssetSeparator)
                );
        }


        public bool IsDirectlyUnderPath(string assetFolder)
        {
            return this.StartsWith(assetFolder + "/", allowPartialWord: false, allowSubfolder: false);
        }

        /// <inheritdoc />
        public bool Equals(IAssetName other)
        {
            return other switch
            {
                null => false,
                AssetName otherImpl => this.ComparableName == otherImpl.ComparableName,
                _ => StringComparer.OrdinalIgnoreCase.Equals(this.Name, other.Name)
            };
        }

        /// <inheritdoc />
        public override int GetHashCode()
        {
            return this.ComparableName.GetHashCode();
        }

        /// <inheritdoc />
        public override string ToString()
        {
            return this.Name;
        }
    }
}