using System.Text.RegularExpressions;
using AcDream.Plugin.Abstractions;

namespace AcDream.Plugins.MossTank;

/// <summary>What a buff line does, which is also how it is toggled.</summary>
public enum BuffTargetKind
{
    Unknown = 0,
    /// <summary>Raises a skill: "Increases the caster's Life Magic skill by 10 points."</summary>
    Skill,
    /// <summary>Raises an attribute: "Increases the caster's Strength by 10 points."</summary>
    Attribute,
    /// <summary>
    /// Defensive self-buff: the elemental/physical protections, and Armor Self.
    /// </summary>
    Protection,
    /// <summary>
    /// A self-cast aura that buffs the wielded weapon or caster — Blood Drinker,
    /// Heart Seeker, Swift Killer, Defender, Spirit Drinker.
    /// </summary>
    Aura,
    /// <summary>
    /// A bane: an Item Enchantment raising armour resistance. Cast by selecting
    /// YOURSELF — retail's own description says "Target yourself to cast this
    /// spell on all of your equipped armor" — so it needs a selection even
    /// though it is, in effect, a self buff.
    /// </summary>
    Bane,
    /// <summary>
    /// A vital regeneration rate buff: Regeneration (health), Rejuvenation
    /// (stamina), Mana Renewal (mana), and their Empyrean/Prodigal kin. All
    /// Life Magic, and cast at the very end of a pass.
    /// </summary>
    Regeneration,
    /// <summary>Any other self-targeted duration buff.</summary>
    Other,
}

/// <summary>One buff line: a family, what it does, and its known tiers.</summary>
public sealed record BuffLine(
    uint Family,
    BuffTargetKind Kind,
    string TargetName,
    List<PluginSpellInfo> Tiers);

/// <summary>
/// Works out what each known self-buff does, straight from retail data.
/// </summary>
/// <remarks>
/// <para>
/// The client's spell table carries no link between a spell and the stat it
/// modifies — that arrives from the server with the enchantment. But retail
/// writes it in the spell's own description, so the classification is derived
/// from shipped data rather than hard-coded:
/// </para>
/// <code>
/// Increases the caster's Life Magic skill by 10 points.   -> Skill
/// Increases the caster's Strength by 10 points.           -> Attribute
/// Reduces damage the caster takes from Fire by 9%.        -> Protection
/// Increases the caster's natural armor by 20 points.      -> Protection
/// Increases a weapon's damage value by 2 points.          -> Aura
/// </code>
/// <para>
/// The irregular naming is why this reads descriptions instead of names:
/// <b>Invulnerability</b> raises Melee Defense, <b>Impregnability</b> raises
/// Missile Defense, <b>Fealty</b> raises Loyalty, <b>Sprint</b> raises Run, and
/// the line called <b>Willpower</b> raises the attribute named <b>Self</b>.
/// </para>
/// <para>
/// <b>Banes are included.</b> They carry no self-targeted flag, but that flag
/// means "needs no selection", not "cannot be cast on you": retail's own text
/// says "Target yourself to cast this spell on all of your equipped armor". So
/// they are classified here and the caller selects the player before casting.
/// </para>
/// </remarks>
public static partial class BuffProfile
{
    [GeneratedRegex(
        @"^Increases (?:the caster's|your) (?<target>.+?)(?<skill>\s+skill)? by ",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex IncreasesPattern();

    [GeneratedRegex(
        @"^Reduces damage (?:the caster|you) takes? from (?<target>.+?) by ",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex ProtectionPattern();

    /// <summary>
    /// Retail's own wording for the weapon/caster auras. Matched on the
    /// description rather than the "Aura of" name prefix so the older
    /// non-aura phrasings classify the same way.
    ///
    /// "magic casting implement's" is the wand buff Aura of Hermetic Link, and
    /// it is the ONLY one of retail's six aura lines that none of the other
    /// alternatives reach -- it was silently landing in Other.
    /// </summary>
    [GeneratedRegex(
        @"\b(a weapon's|weapon or magic caster|magic caster|missile weapon's|magic casting implement's)\b",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex AuraPattern();

    /// <summary>
    /// Banes, matched on retail's own instruction rather than on the word
    /// "Bane": "Target yourself to cast this spell on all of your equipped
    /// armor." That sentence is what says these are cast at the player, which
    /// the self-targeted flag does not.
    /// </summary>
    [GeneratedRegex(
        @"Target yourself to cast this spell on all of your equipped",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex BanePattern();

    /// <summary>
    /// The three vital-rate lines, matched one vital at a time. Retail words
    /// each of them differently and two of the six phrasings do not even begin
    /// with "Increases the caster's":
    /// <code>
    /// Increase caster's natural healing rate by 10%.                 (Regeneration)
    /// Increases your Health Regeneration Rate by 50%.                (Empyrean)
    /// Increases the rate at which the caster regains Stamina by 10%. (Rejuvenation)
    /// Increases your Stamina Regeneration Rate by 50%.               (Empyrean)
    /// Increases the caster's natural mana rate by 10%.               (Mana Renewal)
    /// Increases your Mana Regeneration Rate by 50%.                  (Empyrean)
    /// </code>
    /// Note "Increase", not "Increases", in the health line — retail's own typo,
    /// which is exactly why matching a strict sentence shape lost these.
    /// </summary>
    [GeneratedRegex(
        "natural healing rate|Health Regeneration Rate",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex HealthRegenPattern();

    [GeneratedRegex(
        "rate at which the caster regains Stamina|Stamina Regeneration Rate",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex StaminaRegenPattern();

    [GeneratedRegex(
        "natural mana rate|Mana Regeneration Rate",
        RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex ManaRegenPattern();

    /// <summary>
    /// Retail's spell text says "Assess Monster" where the skill table says
    /// "Assess Creature". Without this the skill silently never matches and its
    /// buff is quietly dropped from every plan.
    /// </summary>
    private static readonly Dictionary<string, string> SkillNameAliases =
        new(StringComparer.OrdinalIgnoreCase)
        {
            ["Assess Monster"] = "Assess Creature",
        };

    /// <summary>The six primary attributes, by the names retail's spells use.</summary>
    private static readonly HashSet<string> AttributeNames =
        new(StringComparer.OrdinalIgnoreCase)
        {
            "Strength", "Endurance", "Quickness", "Coordination", "Focus", "Self",
        };

    /// <summary>
    /// Group the character's known self-buffs into buff lines, keeping only
    /// those that last long enough to be worth maintaining.
    /// </summary>
    public static List<BuffLine> Build(IReadOnlyList<PluginSpellInfo> knownSelfBuffs)
    {
        var byFamily = new Dictionary<uint, BuffLine>();

        foreach (PluginSpellInfo spell in knownSelfBuffs)
        {
            // Instantaneous spells (the vital transfers, heals) are not buffs;
            // they also share families across unrelated lines, so grouping them
            // by family would be wrong twice over.
            if (spell.DurationSeconds <= 0f)
                continue;

            Classify(spell.Description, out BuffTargetKind kind, out string target);
            if (kind == BuffTargetKind.Unknown)
            {
                // Nothing self-targeted is discarded for being unrecognised.
                // Dropping what the patterns do not match is how protections
                // and weapon auras went missing without a word; an unknown
                // spell belongs in Other, which the user can switch on.
                kind = BuffTargetKind.Other;
                target = spell.Name;
            }

            if (!byFamily.TryGetValue(spell.Family, out BuffLine? line))
            {
                line = new BuffLine(spell.Family, kind, target, new List<PluginSpellInfo>());
                byFamily.Add(spell.Family, line);
            }
            line.Tiers.Add(spell);
        }

        foreach (BuffLine line in byFamily.Values)
            line.Tiers.Sort(static (a, b) => b.Tier.CompareTo(a.Tier));   // strongest first

        return byFamily.Values.ToList();
    }

    /// <summary>Classify one spell from its retail description.</summary>
    public static void Classify(
        string? description, out BuffTargetKind kind, out string target)
    {
        kind = BuffTargetKind.Unknown;
        target = string.Empty;
        if (string.IsNullOrWhiteSpace(description))
            return;

        // Banes first: their text also mentions armour resistance, and the
        // "target yourself" instruction is what actually identifies them.
        if (BanePattern().IsMatch(description))
        {
            kind = BuffTargetKind.Bane;
            target = "equipped armor";
            return;
        }

        // Regeneration before the generic "Increases the caster's X by N" match
        // further down, which would otherwise read Mana Renewal as a buff to a
        // stat named "natural mana rate".
        if (HealthRegenPattern().IsMatch(description))
        {
            kind = BuffTargetKind.Regeneration;
            target = "Health";
            return;
        }

        if (StaminaRegenPattern().IsMatch(description))
        {
            kind = BuffTargetKind.Regeneration;
            target = "Stamina";
            return;
        }

        if (ManaRegenPattern().IsMatch(description))
        {
            kind = BuffTargetKind.Regeneration;
            target = "Mana";
            return;
        }

        // Auras next: "Increases a weapon's damage value" would otherwise be
        // read as raising something on the caster.
        if (AuraPattern().IsMatch(description))
        {
            kind = BuffTargetKind.Aura;
            target = "weapon";
            return;
        }

        Match protection = ProtectionPattern().Match(description);
        if (protection.Success)
        {
            kind = BuffTargetKind.Protection;
            target = protection.Groups["target"].Value.Trim();
            return;
        }

        Match increases = IncreasesPattern().Match(description);
        if (!increases.Success)
            return;

        target = increases.Groups["target"].Value.Trim();
        if (target.Length == 0)
            return;

        if (increases.Groups["skill"].Success)
        {
            // The word "skill" is what separates a skill buff from an attribute
            // buff in retail's own wording.
            kind = BuffTargetKind.Skill;
            if (SkillNameAliases.TryGetValue(target, out string? alias))
                target = alias;
            return;
        }

        if (AttributeNames.Contains(target))
        {
            kind = BuffTargetKind.Attribute;
            return;
        }

        // "Increases the caster's natural armor by 20 points" — defensive, but
        // neither a skill nor an attribute.
        kind = target.Contains("armor", StringComparison.OrdinalIgnoreCase)
            ? BuffTargetKind.Protection
            : BuffTargetKind.Other;
    }

    /// <summary>Back-compatible shim for the skill/attribute cases.</summary>
    public static bool TryParseTarget(
        string? description, out BuffTargetKind kind, out string target)
    {
        Classify(description, out kind, out target);
        return kind != BuffTargetKind.Unknown;
    }
}