using System.Text.Json;
using System.Text.RegularExpressions;
using SQLInsight.Core.Instances;

namespace SQLInsight.Collectors.Tests;

/// <summary>
/// SQL Server 2005 cannot run in CI (no container image), and its T-SQL lacks much of 2008's. Every collector that can
/// run on 2005 (all its required capabilities exist from 9.0) is checked for 2008+ syntax in its SQL, and so is every
/// community rule that does not ask for 10.0 or later. A collector with version branches must keep 2008+ syntax in the
/// branch for newer versions; those few are listed with what they gate.
/// </summary>
public sealed partial class Sql2005CompatibilityTests
{
    /// <summary>2008+ constructs that make a whole batch fail on 2005, whatever branch it was meant for.</summary>
    private static readonly (string Name, Regex Pattern)[] Sql2008Only =
    [
        ("DECLARE med startværdi", new Regex(@"DECLARE\s+@\w+\s+\w+(\s*\([\d\s,]+\))?\s*=", RegexOptions.IgnoreCase)),
        ("+= / -= på variabel", new Regex(@"@\w+\s*[+\-*/]=", RegexOptions.IgnoreCase)),
        ("MERGE", new Regex(@"\bMERGE\s", RegexOptions.IgnoreCase)),
        ("CONCAT/IIF/CHOOSE/FORMAT/TRY_*", new Regex(@"\b(CONCAT|IIF|CHOOSE|FORMAT|TRY_CONVERT|TRY_CAST|TRY_PARSE|EOMONTH|DATEFROMPARTS|STRING_AGG|STRING_SPLIT)\s*\(", RegexOptions.IgnoreCase)),
        ("OFFSET … FETCH", new Regex(@"\bOFFSET\s+\S+\s+ROWS\b", RegexOptions.IgnoreCase)),
        ("date/time/datetime2/datetimeoffset", new Regex(@"\bAS\s+(date|time|datetime2|datetimeoffset)\b|\b(datetime2|datetimeoffset)\s*\(", RegexOptions.IgnoreCase)),
        ("VALUES med flere rækker", new Regex(@"\bVALUES\s*\([^)]*\)\s*,\s*\(", RegexOptions.IgnoreCase)),
    ];

    /// <summary>
    /// Collectors that run on 2005 but deliberately contain 2008+ syntax in a branch that 2005 never takes.
    /// Only patterns from <see cref="Sql2008Only"/> listed here are tolerated, and only in that file.
    /// </summary>
    private static readonly Dictionary<string, string[]> VersionBranched = new(StringComparer.Ordinal)
    {
        // Query Store queries only run when Capability.QueryStore is present (2016+).
        ["QueryStoreCollector"] = ["DECLARE med startværdi", "date/time/datetime2/datetimeoffset"],
    };

    [Fact]
    public void Collectors_that_run_on_sql_server_2005_use_only_2005_syntax()
    {
        var problems = new List<string>();
        foreach (var collector in BuiltInCollectors.Create())
        {
            var runsOn2005 = collector.RequiredCapabilities.All(c => InstanceCapabilities.MinimumVersionFor(c) is not { Major: > 9 });
            if (!runsOn2005)
            {
                continue;
            }

            var name = collector.GetType().Name;
            var source = SourceOf(name);
            VersionBranched.TryGetValue(name, out var tolerated);
            foreach (Match literal in RawString().Matches(source))
            {
                foreach (var (pattern, regex) in Sql2008Only)
                {
                    if (regex.IsMatch(literal.Value) && tolerated?.Contains(pattern) != true)
                    {
                        problems.Add($"{name}: {pattern}");
                    }
                }
            }
        }

        Assert.True(problems.Count == 0, "SQL Server 2008+-syntaks i SQL, der også køres på 2005: " + string.Join("; ", problems.Distinct()));
    }

    [Fact]
    public void Community_rules_for_sql_server_2005_use_only_2005_syntax()
    {
        var problems = new List<string>();
        foreach (var file in Directory.EnumerateFiles(Path.Combine(RepositoryRoot(), "rules", "community"), "*.json"))
        {
            using var document = JsonDocument.Parse(File.ReadAllText(file), new JsonDocumentOptions { CommentHandling = JsonCommentHandling.Skip, AllowTrailingCommas = true });
            var rules = document.RootElement.ValueKind == JsonValueKind.Array ? document.RootElement.EnumerateArray().ToList() : [document.RootElement];
            foreach (var rule in rules)
            {
                var minimum = rule.TryGetProperty("minimumVersion", out var v) ? v.GetString() : "9.0";
                if (SqlServerVersion.Parse(minimum + ".0.0").Major > 9)
                {
                    continue;
                }

                var query = rule.GetProperty("query").GetString()!;
                problems.AddRange(Sql2008Only.Where(p => p.Pattern.IsMatch(query)).Select(p => $"{rule.GetProperty("id").GetString()}: {p.Name}"));
            }
        }

        Assert.True(problems.Count == 0, "SQL Server 2008+-syntaks i regler uden minimumVersion 10.0: " + string.Join("; ", problems));
    }

    [Fact]
    public void Plan_analysis_and_top_sql_identify_statements_without_query_hash_on_2005()
    {
        var sql2005 = new[]
        {
            Performance.PlanAnalysisCollector.BuildSql(memoryColumns: false, queryHash: false),
            Performance.QueryStatsCollector.SqlFor(SqlServerVersion.Parse("9.0.5057.0"), new DateTime(2026, 10, 1)),
        };

        Assert.All(sql2005, sql => Assert.DoesNotContain("query_hash", sql, StringComparison.OrdinalIgnoreCase));
        Assert.All(sql2005, sql => Assert.Contains("sys.fn_varbintohexstr(", sql, StringComparison.Ordinal));
        Assert.Contains("query_hash", Performance.PlanAnalysisCollector.BuildSql(memoryColumns: true), StringComparison.Ordinal);
    }

    [Theory]
    [InlineData("DECLARE @since int = CONVERT(int, 1);", true)]
    [InlineData("DECLARE @x nvarchar(60) = N'a';", true)]
    [InlineData("DECLARE @since int;\nSET @since = 1;", false)]
    [InlineData("SET @n += 1", true)]
    [InlineData("SELECT CONVERT(datetime, '2026-10-01', 126)", false)]
    public void The_check_itself_recognises_2008_syntax(string sql, bool expected) =>
        Assert.Equal(expected, Sql2008Only.Any(p => p.Pattern.IsMatch(sql)));

    private static string SourceOf(string typeName)
    {
        var folder = Path.Combine(RepositoryRoot(), "src", "SQLInsight.Collectors");
        var file = Directory.EnumerateFiles(folder, typeName + ".cs", SearchOption.AllDirectories).SingleOrDefault();
        return file is null ? throw new InvalidOperationException($"{typeName}.cs ikke fundet") : File.ReadAllText(file);
    }

    private static string RepositoryRoot()
    {
        var root = AppContext.BaseDirectory;
        while (!File.Exists(Path.Combine(root, "SQLInsight.slnx")))
        {
            root = Path.GetDirectoryName(root) ?? throw new InvalidOperationException("SQLInsight.slnx ikke fundet.");
        }

        return root;
    }

    // C# raw string literals ("""…""" and $"""…"""): where the collectors keep their SQL.
    [GeneratedRegex("\"\"\"(.*?)\"\"\"", RegexOptions.Singleline)]
    private static partial Regex RawString();
}