using System.Globalization;
using ClawdDotNet.Core.Storage;
using Microsoft.Data.Sqlite;

namespace ClawdDotNet.Core.Audit;

/// <summary>
/// Das Audit-Log in der Instanz-Datenbank. Bewusst nur Einfügen und Lesen — es gibt keine
/// Update-/Delete-Methoden, weil die Unveränderlichkeit die eigentliche Zusage ist.
/// </summary>
public sealed class SqliteAuditRepository : IAuditRepository
{
    private readonly SqliteStorage _storage;

    public SqliteAuditRepository(SqliteStorage storage) => _storage = storage;

    public Task AppendAsync(AuditEntry entry, CancellationToken ct)
        => _storage.WriteAsync(async conn =>
        {
            using var cmd = conn.CreateCommand();
            cmd.CommandText = """
                INSERT INTO AuditLog
                    (RunId, CallId, AgentId, Model, Source, Tool, Arguments, Status, Summary, DurationMs, OccurredAt)
                VALUES
                    (@runId, @callId, @agentId, @model, @source, @tool, @arguments, @status, @summary, @durationMs, @occurredAt)
                """;
            cmd.Parameters.AddWithValue("@runId", entry.RunId);
            cmd.Parameters.AddWithValue("@callId", entry.CallId);
            cmd.Parameters.AddWithValue("@agentId", entry.AgentId);
            cmd.Parameters.AddWithValue("@model", entry.Model);
            cmd.Parameters.AddWithValue("@source", AuditSource.Normalize(entry.Source));
            cmd.Parameters.AddWithValue("@tool", entry.Tool);
            cmd.Parameters.AddWithValue("@arguments", entry.Arguments);
            cmd.Parameters.AddWithValue("@status", entry.Status.ToString());
            cmd.Parameters.AddWithValue("@summary", entry.Summary);
            cmd.Parameters.AddWithValue("@durationMs", entry.DurationMs);
            cmd.Parameters.AddWithValue("@occurredAt", Format(entry.OccurredAt));
            await cmd.ExecuteNonQueryAsync(ct);
        }, ct);

    public Task RecordReceiptAsync(RunReceipt receipt, CancellationToken ct)
        => _storage.WriteAsync(async conn =>
        {
            using var cmd = conn.CreateCommand();
            cmd.CommandText = """
                INSERT INTO RunReceipts
                    (RunId, AgentId, Model, Source, TaskId, Status, StepCount,
                     PromptTokens, CompletionTokens, CachedTokens, CostUsd, CostIsKnown,
                     DurationMs, ResultRef, OccurredAt, CallerRunId, BudgetPot)
                VALUES
                    (@runId, @agentId, @model, @source, @taskId, @status, @stepCount,
                     @prompt, @completion, @cached, @cost, @costKnown,
                     @durationMs, @resultRef, @occurredAt, @callerRunId, @budgetPot)
                """;
            cmd.Parameters.AddWithValue("@runId", receipt.RunId);
            cmd.Parameters.AddWithValue("@agentId", receipt.AgentId);
            cmd.Parameters.AddWithValue("@model", receipt.Model);
            cmd.Parameters.AddWithValue("@source", AuditSource.Normalize(receipt.Source));
            cmd.Parameters.AddWithValue("@taskId", (object?)receipt.TaskId ?? DBNull.Value);
            cmd.Parameters.AddWithValue("@status", receipt.Status);
            cmd.Parameters.AddWithValue("@stepCount", receipt.StepCount);
            cmd.Parameters.AddWithValue("@prompt", receipt.PromptTokens);
            cmd.Parameters.AddWithValue("@completion", receipt.CompletionTokens);
            cmd.Parameters.AddWithValue("@cached", receipt.CachedTokens);
            cmd.Parameters.AddWithValue("@cost", receipt.CostUsd.ToString(CultureInfo.InvariantCulture));
            cmd.Parameters.AddWithValue("@costKnown", receipt.CostIsKnown ? 1 : 0);
            cmd.Parameters.AddWithValue("@durationMs", receipt.DurationMs);
            cmd.Parameters.AddWithValue("@resultRef", receipt.ResultRef);
            cmd.Parameters.AddWithValue("@occurredAt", Format(receipt.OccurredAt));
            cmd.Parameters.AddWithValue("@callerRunId", (object?)receipt.CallerRunId ?? DBNull.Value);
            cmd.Parameters.AddWithValue("@budgetPot", (object?)receipt.BudgetPot ?? DBNull.Value);
            await cmd.ExecuteNonQueryAsync(ct);
        }, ct);

    public async Task<IReadOnlyList<AuditEntry>> ListRecentAsync(int limit, CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT " + AuditColumns + " FROM AuditLog ORDER BY Id DESC LIMIT @limit";
        cmd.Parameters.AddWithValue("@limit", Math.Clamp(limit, 1, 1000));
        return await ReadEntriesAsync(cmd, ct);
    }

    public async Task<IReadOnlyList<AuditEntry>> ListForRunAsync(string runId, CancellationToken ct)
    {
        await using (var conn = await _storage.OpenConnectionAsync(ct))
        {
            using var cmd = conn.CreateCommand();
            cmd.CommandText = "SELECT " + AuditColumns + " FROM AuditLog WHERE RunId = @runId ORDER BY Id";
            cmd.Parameters.AddWithValue("@runId", runId);
            var hot = await ReadEntriesAsync(cmd, ct);
            if (hot.Count > 0)
                return hot;
        }

        // #700: an older run moved to the archive — it is still evidence and still found.
        foreach (var archive in ArchiveConnections())
            await using (archive)
            {
                using var cmd = archive.CreateCommand();
                cmd.CommandText = "SELECT " + AuditColumns + " FROM AuditLog WHERE RunId = @runId ORDER BY Id";
                cmd.Parameters.AddWithValue("@runId", runId);
                var found = await ReadEntriesAsync(cmd, ct);
                if (found.Count > 0)
                    return found;
            }
        return [];
    }

    public async Task<RunReceipt?> GetReceiptForRunAsync(string runId, CancellationToken ct)
    {
        await using (var conn = await _storage.OpenConnectionAsync(ct))
        {
            using var cmd = conn.CreateCommand();
            cmd.CommandText = "SELECT " + ReceiptColumns + " FROM RunReceipts WHERE RunId = @runId ORDER BY Id DESC LIMIT 1";
            cmd.Parameters.AddWithValue("@runId", runId);
            await using var reader = await cmd.ExecuteReaderAsync(ct);
            if (await reader.ReadAsync(ct))
                return ReadReceipt(reader);
        }

        foreach (var archive in ArchiveConnections())
            await using (archive)
            {
                using var cmd = archive.CreateCommand();
                cmd.CommandText = "SELECT " + ReceiptColumns + " FROM RunReceipts WHERE RunId = @runId ORDER BY Id DESC LIMIT 1";
                cmd.Parameters.AddWithValue("@runId", runId);
                await using var reader = await cmd.ExecuteReaderAsync(ct);
                if (await reader.ReadAsync(ct))
                    return ReadReceipt(reader);
            }
        return null;
    }

    /// <summary>
    /// #700: The month archives, newest first, opened read-only one at a time. A lookup by run
    /// is rare and asks for one run — opening a few small files for it is cheap.
    /// </summary>
    private IEnumerable<SqliteConnection> ArchiveConnections()
    {
        foreach (var file in AuditArchive.FilesIn(AuditArchive.ArchiveDirectoryOf(_storage)))
        {
            var connection = new SqliteConnection(new SqliteConnectionStringBuilder
            {
                DataSource = Path.Combine(AuditArchive.ArchiveDirectoryOf(_storage), file.FileName),
                Mode = SqliteOpenMode.ReadOnly,
                Pooling = false
            }.ToString());
            connection.Open();
            yield return connection;
        }
    }

    public async Task<IReadOnlyList<RunReceipt>> ListReceiptsAsync(DateTime fromUtc, DateTime toUtc, int limit, CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        // OccurredAt is ISO-8601 UTC ("O"), so the text comparison is a time comparison.
        cmd.CommandText = "SELECT " + ReceiptColumns +
                          " FROM RunReceipts WHERE OccurredAt >= @from AND OccurredAt < @to ORDER BY OccurredAt LIMIT @limit";
        cmd.Parameters.AddWithValue("@from", Format(fromUtc));
        cmd.Parameters.AddWithValue("@to", Format(toUtc));
        cmd.Parameters.AddWithValue("@limit", limit);

        var results = new List<RunReceipt>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
            results.Add(ReadReceipt(reader));
        return results;
    }

    public async Task<IReadOnlyList<RunReceipt>> ListReceiptsCalledFromAsync(string runId, CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT " + ReceiptColumns + " FROM RunReceipts WHERE CallerRunId = @runId ORDER BY Id";
        cmd.Parameters.AddWithValue("@runId", runId);

        var results = new List<RunReceipt>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
            results.Add(ReadReceipt(reader));
        return results;
    }

    public async Task<IReadOnlyList<RunReceipt>> ListReceiptsForTaskAsync(string taskId, CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT " + ReceiptColumns + " FROM RunReceipts WHERE TaskId = @taskId ORDER BY Id";
        cmd.Parameters.AddWithValue("@taskId", taskId);

        var results = new List<RunReceipt>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
            results.Add(ReadReceipt(reader));
        return results;
    }

    public async Task<int> CountAsync(CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT COUNT(*) FROM AuditLog";
        return Convert.ToInt32(await cmd.ExecuteScalarAsync(ct));
    }

    /// <summary>
    /// Offene Aufrufe (#554): ein <c>Started</c>, zu dem kein späterer Eintrag mit
    /// derselben CallId existiert.
    ///
    /// <para>Einträge ohne CallId bleiben außen vor — sie stammen aus der Zeit vor #554
    /// und ließen sich nicht paaren. Sie alle als offen zu melden, wäre schlimmer als
    /// sie zu übergehen: Der erste Start nach der Aktualisierung legte sonst das ganze
    /// Altprotokoll zur Prüfung vor.</para>
    /// </summary>
    public async Task<IReadOnlyList<AuditEntry>> ListOpenCallsAsync(CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = $"""
            SELECT {AuditColumns} FROM AuditLog a
            WHERE a.Status = 'Started'
              AND a.CallId <> ''
              AND NOT EXISTS (
                  SELECT 1 FROM AuditLog b
                  WHERE b.CallId = a.CallId
                    AND b.Id > a.Id
                    AND b.Status <> 'Started'
              )
            ORDER BY a.Id
            """;
        return await ReadEntriesAsync(cmd, ct);
    }

    public async Task<IReadOnlyList<AuditEntry>> ListForAgentAsync(
        string agentId, DateTime? seit, int limit, CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = $"""
            SELECT {AuditColumns} FROM AuditLog
            WHERE AgentId = @agentId
              AND (@seit IS NULL OR OccurredAt >= @seit)
            ORDER BY Id DESC
            LIMIT @limit
            """;
        cmd.Parameters.AddWithValue("@agentId", agentId);
        cmd.Parameters.AddWithValue("@seit", seit is { } s ? Format(s) : DBNull.Value);
        cmd.Parameters.AddWithValue("@limit", limit);
        return await ReadEntriesAsync(cmd, ct);
    }

    /// <summary>
    /// Kennzahlen je Agent und Werkzeug (#556).
    ///
    /// <para>Die Dauer wird nur über abgeschlossene Aufrufe gemittelt. Ein
    /// <c>Started</c>-Eintrag trägt die Dauer 0, weil zum Zeitpunkt des Schreibens noch
    /// nichts gelaufen war — würde er mitgezählt, sähe jedes Werkzeug doppelt so schnell
    /// aus, wie es ist.</para>
    /// </summary>
    public async Task<IReadOnlyList<ToolUsageStat>> SummarizeToolUsageAsync(
        string? agentId, DateTime? seit, CancellationToken ct)
    {
        await using var conn = await _storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = """
            SELECT AgentId, Tool,
                   SUM(CASE WHEN Status <> 'Started' THEN 1 ELSE 0 END)            AS Calls,
                   SUM(CASE WHEN Status = 'Error'    THEN 1 ELSE 0 END)            AS Failed,
                   SUM(CASE WHEN Status = 'Denied'   THEN 1 ELSE 0 END)            AS Denied,
                   SUM(CASE WHEN Status = 'Started'  THEN 1 ELSE 0 END)            AS Begonnen,
                   SUM(CASE WHEN Status <> 'Started' THEN DurationMs ELSE 0 END)   AS GesamtMs,
                   MAX(DurationMs)                                                 AS MaxMs
            FROM AuditLog
            WHERE (@agentId IS NULL OR AgentId = @agentId)
              AND (@seit    IS NULL OR OccurredAt >= @seit)
            GROUP BY AgentId, Tool
            ORDER BY Calls DESC
            """;
        cmd.Parameters.AddWithValue("@agentId", (object?)agentId ?? DBNull.Value);
        cmd.Parameters.AddWithValue("@seit", seit is { } s ? Format(s) : DBNull.Value);

        var results = new List<ToolUsageStat>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
        {
            var abgeschlossen = reader.GetInt32(2);
            var begonnen = reader.GetInt32(5);

            results.Add(new ToolUsageStat
            {
                AgentId = reader.GetString(0),
                Tool = reader.GetString(1),
                Calls = abgeschlossen,
                Failed = reader.GetInt32(3),
                Denied = reader.GetInt32(4),

                // Begonnene minus abgeschlossene: Was übrig bleibt, hat nie geendet.
                // Nie negativ — ein Abschluss ohne Start kann es nicht geben, aber
                // Alteinträge ohne Started-Zeile gibt es sehr wohl.
                Unfinished = Math.Max(0, begonnen - abgeschlossen),

                TotalDurationMs = reader.GetInt64(6),
                MaxDurationMs = reader.GetInt64(7)
            });
        }
        return results;
    }

    // ─── Hilfsfunktionen ───

    private const string AuditColumns =
        "Id, RunId, AgentId, Model, Source, Tool, Arguments, Status, Summary, DurationMs, OccurredAt, CallId";

    private const string ReceiptColumns =
        "Id, RunId, AgentId, Model, Source, TaskId, Status, StepCount, PromptTokens, " +
        "CompletionTokens, CachedTokens, CostUsd, CostIsKnown, DurationMs, ResultRef, OccurredAt, CallerRunId, BudgetPot";

    private static async Task<IReadOnlyList<AuditEntry>> ReadEntriesAsync(SqliteCommand cmd, CancellationToken ct)
    {
        var results = new List<AuditEntry>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
            results.Add(ReadEntry(reader));
        return results;
    }

    private static AuditEntry ReadEntry(SqliteDataReader r) => new()
    {
        Id = r.GetInt64(0),
        RunId = r.GetString(1),
        AgentId = r.GetString(2),
        Model = r.GetString(3),
        Source = r.GetString(4),
        Tool = r.GetString(5),
        Arguments = r.GetString(6),
        Status = Enum.TryParse<AuditStatus>(r.GetString(7), out var s) ? s : AuditStatus.Ok,
        Summary = r.GetString(8),
        DurationMs = r.GetInt64(9),
        OccurredAt = Parse(r.GetString(10)),
        CallId = r.GetString(11)
    };

    private static RunReceipt ReadReceipt(SqliteDataReader r) => new()
    {
        Id = r.GetInt64(0),
        RunId = r.GetString(1),
        AgentId = r.GetString(2),
        Model = r.GetString(3),
        Source = r.GetString(4),
        TaskId = r.IsDBNull(5) ? null : r.GetString(5),
        Status = r.GetString(6),
        StepCount = r.GetInt32(7),
        PromptTokens = r.GetInt32(8),
        CompletionTokens = r.GetInt32(9),
        CachedTokens = r.GetInt32(10),
        CostUsd = decimal.TryParse(r.GetString(11), NumberStyles.Any, CultureInfo.InvariantCulture, out var c) ? c : 0m,
        CostIsKnown = r.GetInt32(12) != 0,
        DurationMs = r.GetInt64(13),
        ResultRef = r.GetString(14),
        OccurredAt = Parse(r.GetString(15)),
        CallerRunId = r.IsDBNull(16) ? null : r.GetString(16),
        BudgetPot = r.IsDBNull(17) ? null : r.GetString(17)
    };

    private static string Format(DateTime value) => value.ToUniversalTime().ToString("O");

    private static DateTime Parse(string value)
        => DateTime.TryParse(value, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out var dt)
            ? dt
            : DateTime.MinValue;
}