namespace Mr.BrickAdventures.Progression;

/// <summary>
/// The authored upgrade table for every Skill: what each level costs to reach. Built from
/// <c>SkillData</c> resources by an adapter — same pattern as <see cref="Campaign"/>, so no port is
/// needed and a test can construct one directly.
/// </summary>
public sealed class SkillCatalogue
{
    private readonly Dictionary<SkillId, IReadOnlyList<Coins>> _costs;

    private SkillCatalogue(Dictionary<SkillId, IReadOnlyList<Coins>> costs) => _costs = costs;

    public static SkillCatalogue Empty() => new(new Dictionary<SkillId, IReadOnlyList<Coins>>());

    /// <summary>
    /// Builds a catalogue. Each Skill's list is the cost to reach level 1, level 2, and so on, so a
    /// Skill with an empty list cannot be bought at all.
    /// </summary>
    public static SkillCatalogue Of(IReadOnlyDictionary<SkillId, IReadOnlyList<Coins>> costsByLevel) =>
        new(costsByLevel.ToDictionary(e => e.Key, e => e.Value));

    /// <summary>
    /// The highest level this Skill can reach, or null when it has no authored upgrades and so
    /// cannot be bought. Returning null is what stops <c>Upgrades[0].Cost</c> from throwing on the
    /// five Skills that currently have no upgrade entries.
    /// </summary>
    public SkillLevel? MaxLevelOf(SkillId skill) =>
        _costs.TryGetValue(skill, out var costs) && costs.Count > 0
            ? SkillLevel.Of(costs.Count)
            : null;

    /// <summary>
    /// What it costs to reach <paramref name="level"/>, or null if this Skill does not go that high.
    /// </summary>
    public Coins? CostToReach(SkillId skill, SkillLevel level) =>
        _costs.TryGetValue(skill, out var costs) && level.Value <= costs.Count
            ? costs[level.Value - 1]
            : null;
}