using System.Text;

namespace BlueLaminate.Core.SkinLand;

/// <summary>
/// Builds a skin.land market URL from the catalogue's weapon + skin + wear. skin.land's
/// market routes are <c>/market/csgo/{slug}/</c> where the slug is simply
/// <c>{weapon}-{skin}-{wear}</c> kebab-cased — verified against the live site (e.g.
/// "M4A4" + "Global Offensive" + "Battle-Scarred" → <c>m4a4-global-offensive-battle-scarred</c>,
/// "AK-47" + "Redline" + "Field-Tested" → <c>ak-47-redline-field-tested</c>). No discovery
/// or stored mapping is needed.
/// <para>
/// StatTrak and Souvenir are <em>separate</em> pages on skin.land (<c>stattrak-</c>/
/// <c>souvenir-</c> prefixed slugs); this builds the base (non-special) page, which is the
/// unit v1 sweeps per <c>SkinCondition</c>.
/// </para>
/// </summary>
public static class SkinLandSlug
{
    private const string MarketBase = "https://skin.land/market/csgo/";

    /// <summary>"M4A4", "Global Offensive", "Battle-Scarred" → the full market URL.</summary>
    public static string MarketUrl(string weapon, string skinName, string condition) =>
        $"{MarketBase}{Slugify($"{weapon} {skinName} {condition}")}/";

    /// <summary>
    /// Lowercase, collapse every run of non-alphanumeric characters to a single hyphen,
    /// and trim leading/trailing hyphens. So "AK-47 | Redline (Field-Tested)" and the
    /// catalogue's "AK-47 Redline Field-Tested" both reduce to "ak-47-redline-field-tested".
    /// <para>
    /// The apostrophe is the one exception: skin.land keeps it literally in the slug rather
    /// than collapsing it to a hyphen (verified live — "AWP | Man-o'-war" →
    /// <c>awp-man-o'-war</c>, "AUG | Lil' Pig" → <c>aug-lil'-pig</c>; the collapsed
    /// <c>man-o-war</c>/<c>lil-pig</c> forms 404). Both the ASCII (') and typographic (’)
    /// apostrophe normalize to a literal ASCII apostrophe in the slug.
    /// </para>
    /// </summary>
    public static string Slugify(string value)
    {
        var sb = new StringBuilder(value.Length);
        var pendingHyphen = false;
        foreach (var ch in value)
        {
            if (ch is '\'' or '’')
            {
                // skin.land preserves the apostrophe as part of the word — emit it literally,
                // and don't let it trigger a hyphen on either side.
                sb.Append('\'');
                pendingHyphen = false;
            }
            else if (char.IsLetterOrDigit(ch))
            {
                if (pendingHyphen && sb.Length > 0)
                {
                    sb.Append('-');
                }

                sb.Append(char.ToLowerInvariant(ch));
                pendingHyphen = false;
            }
            else
            {
                pendingHyphen = true;
            }
        }

        return sb.ToString();
    }
}