using System.Globalization;
using System.Text.Json.Serialization;
using ClawdDotNet.Core.Storage;
using Microsoft.Data.Sqlite;
using Microsoft.Extensions.Logging;

namespace ClawdDotNet.Core.Audit;

/// <summary>#700: How long audit and receipts stay in the working database (<c>auditArchive</c> in the instance settings).</summary>
public sealed class AuditArchiveSettings
{
    /// <summary>
    /// Days a run stays in the working database; older ones move to the monthly archive.
    /// 0 keeps everything in the working database. Nothing is ever deleted either way.
    /// </summary>
    [JsonPropertyName("hotDays")]
    public int HotDays { get; set; } = 180;
}

/// <summary>#700: One day of one agent, condensed — stays in the working database for good.</summary>
public sealed record RunDay(
    string Day, string AgentId, string UnitId, int Runs, int Failed, int LoopLimit,
    long PromptTokens, long CompletionTokens, decimal CostUsd, int ToolCalls, int ToolErrors, int Denied, int Staged);

/// <summary>An archive file as the administration shows it.</summary>
public sealed record AuditArchiveFile(string Month, string FileName, long Bytes);

/// <summary>
/// #700: The audit is evidence, and evidence is kept — the user's decision of 2026-09-22: as
/// little deleted as possible. Five years after a failed project, how it came about can be read:
/// which task was worded how, what the agent read, who approved what. That is the one real
/// advantage an organisation of agents has over one of people.
///
/// <para><b>What grows is the working table, not the disk.</b> A hundred agents write some
/// 7,400 audit rows a day; every supervision and every view reads those tables. So rows older
/// than <see cref="AuditArchiveSettings.HotDays"/> move — never get deleted — into one SQLite
/// file per month under <c>Archive/</c>, which the backup takes along like any other file.
/// Looking up a run finds them there.</para>
///
/// <para><b>Day values stay.</b> Before rows move, each day is condensed per agent and unit
/// (<see cref="RunDay"/>): runs, failures, tokens, costs, tool calls. Most questions over months
/// are answered from those, without opening an archive. The unit is taken when the day is
/// condensed — later "what did marketing cost in March" cannot be answered otherwise.</para>
/// </summary>
public sealed class AuditArchive(
    SqliteStorage storage,
    Func<AuditArchiveSettings> settings,
    Func<string, string?> unitOf,
    ILogger logger,
    TimeProvider? clock = null) : IAsyncDisposable
{
    public const string FolderName = "Archive";

    private readonly TimeProvider _clock = clock ?? TimeProvider.System;

    public string Directory => ArchiveDirectoryOf(storage);

    public static string ArchiveDirectoryOf(SqliteStorage storage)
        => Path.Combine(Path.GetDirectoryName(Path.GetFullPath(storage.DatabasePath))!, FolderName);

    public static string FileNameOf(string month) => $"audit-{month}.db";

    private DateTime Now => _clock.GetUtcNow().UtcDateTime;

    // ─── Day values ───

    /// <summary>
    /// Condenses every day before today that is not condensed yet — and the last two again,
    /// because a run can end after midnight. Days are UTC days.
    /// </summary>
    public async Task<int> CondenseAsync(CancellationToken ct)
    {
        var today = Now.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture);
        return await storage.WriteAsync(async conn =>
        {
            string? last;
            using (var max = conn.CreateCommand())
            {
                max.CommandText = "SELECT MAX(Day) FROM RunDaily";
                last = await max.ExecuteScalarAsync(ct) as string;
            }
            var from = last is null ? "" : DateOnly.ParseExact(last, "yyyy-MM-dd", CultureInfo.InvariantCulture).AddDays(-1).ToString("yyyy-MM-dd", CultureInfo.InvariantCulture);

            var days = new Dictionary<(string Day, string Agent), RunDayBuilder>();
            using (var receipts = conn.CreateCommand())
            {
                receipts.CommandText = """
                    SELECT substr(OccurredAt, 1, 10) AS Day, AgentId,
                           SUM(CASE WHEN Status IN ('BudgetExceeded', 'TargetBusy', 'ShuttingDown') THEN 0 ELSE 1 END),
                           SUM(CASE WHEN Status IN ('Failed', 'Cancelled', 'Incomplete') THEN 1 ELSE 0 END),
                           SUM(CASE WHEN Status = 'LoopLimitExceeded' THEN 1 ELSE 0 END),
                           SUM(PromptTokens), SUM(CompletionTokens), GROUP_CONCAT(CostUsd, ';')
                    FROM RunReceipts
                    WHERE substr(OccurredAt, 1, 10) >= @from AND substr(OccurredAt, 1, 10) < @today
                    GROUP BY Day, AgentId
                    """;
                receipts.Parameters.AddWithValue("@from", from);
                receipts.Parameters.AddWithValue("@today", today);
                await using var r = await receipts.ExecuteReaderAsync(ct);
                while (await r.ReadAsync(ct))
                {
                    var b = Builder(days, r.GetString(0), r.GetString(1));
                    b.Runs = r.GetInt32(2);
                    b.Failed = r.GetInt32(3);
                    b.LoopLimit = r.GetInt32(4);
                    b.PromptTokens = r.GetInt64(5);
                    b.CompletionTokens = r.GetInt64(6);
                    b.CostUsd = r.IsDBNull(7) ? 0m : r.GetString(7).Split(';').Sum(c =>
                        decimal.TryParse(c, NumberStyles.Any, CultureInfo.InvariantCulture, out var v) ? v : 0m);
                }
            }
            using (var audit = conn.CreateCommand())
            {
                audit.CommandText = """
                    SELECT substr(OccurredAt, 1, 10) AS Day, AgentId,
                           SUM(CASE WHEN Status NOT IN ('Started', 'Staged', 'Denied') THEN 1 ELSE 0 END),
                           SUM(CASE WHEN Status = 'Error' THEN 1 ELSE 0 END),
                           SUM(CASE WHEN Status = 'Denied' THEN 1 ELSE 0 END),
                           SUM(CASE WHEN Status = 'Staged' THEN 1 ELSE 0 END)
                    FROM AuditLog
                    WHERE substr(OccurredAt, 1, 10) >= @from AND substr(OccurredAt, 1, 10) < @today AND AgentId <> ''
                    GROUP BY Day, AgentId
                    """;
                audit.Parameters.AddWithValue("@from", from);
                audit.Parameters.AddWithValue("@today", today);
                await using var r = await audit.ExecuteReaderAsync(ct);
                while (await r.ReadAsync(ct))
                {
                    var b = Builder(days, r.GetString(0), r.GetString(1));
                    b.ToolCalls = r.GetInt32(2);
                    b.ToolErrors = r.GetInt32(3);
                    b.Denied = r.GetInt32(4);
                    b.Staged = r.GetInt32(5);
                }
            }

            foreach (var ((day, agent), b) in days)
            {
                using var upsert = conn.CreateCommand();
                upsert.CommandText = """
                    INSERT INTO RunDaily (Day, AgentId, UnitId, Runs, Failed, LoopLimit, PromptTokens, CompletionTokens,
                                          CostUsd, ToolCalls, ToolErrors, Denied, Staged)
                    VALUES (@day, @agent, @unit, @runs, @failed, @loop, @prompt, @completion, @cost, @calls, @errors, @denied, @staged)
                    ON CONFLICT (Day, AgentId) DO UPDATE SET
                        Runs = excluded.Runs, Failed = excluded.Failed, LoopLimit = excluded.LoopLimit,
                        PromptTokens = excluded.PromptTokens, CompletionTokens = excluded.CompletionTokens,
                        CostUsd = excluded.CostUsd, ToolCalls = excluded.ToolCalls, ToolErrors = excluded.ToolErrors,
                        Denied = excluded.Denied, Staged = excluded.Staged
                    """;
                // The unit stays what it was when the day was first condensed.
                upsert.Parameters.AddWithValue("@day", day);
                upsert.Parameters.AddWithValue("@agent", agent);
                upsert.Parameters.AddWithValue("@unit", unitOf(agent) ?? "");
                upsert.Parameters.AddWithValue("@runs", b.Runs);
                upsert.Parameters.AddWithValue("@failed", b.Failed);
                upsert.Parameters.AddWithValue("@loop", b.LoopLimit);
                upsert.Parameters.AddWithValue("@prompt", b.PromptTokens);
                upsert.Parameters.AddWithValue("@completion", b.CompletionTokens);
                upsert.Parameters.AddWithValue("@cost", b.CostUsd.ToString(CultureInfo.InvariantCulture));
                upsert.Parameters.AddWithValue("@calls", b.ToolCalls);
                upsert.Parameters.AddWithValue("@errors", b.ToolErrors);
                upsert.Parameters.AddWithValue("@denied", b.Denied);
                upsert.Parameters.AddWithValue("@staged", b.Staged);
                await upsert.ExecuteNonQueryAsync(ct);
            }
            return days.Count;
        }, ct);
    }

    private sealed class RunDayBuilder
    {
        public int Runs, Failed, LoopLimit, ToolCalls, ToolErrors, Denied, Staged;
        public long PromptTokens, CompletionTokens;
        public decimal CostUsd;
    }

    private static RunDayBuilder Builder(Dictionary<(string, string), RunDayBuilder> days, string day, string agent)
    {
        if (!days.TryGetValue((day, agent), out var b))
            days[(day, agent)] = b = new RunDayBuilder();
        return b;
    }

    /// <summary>Day values in a range (inclusive), optionally for one agent or one unit.</summary>
    public async Task<IReadOnlyList<RunDay>> DaysAsync(DateOnly from, DateOnly to, string? agentId, string? unitId, CancellationToken ct)
    {
        await using var conn = await storage.OpenConnectionAsync(ct);
        using var cmd = conn.CreateCommand();
        cmd.CommandText = """
            SELECT Day, AgentId, UnitId, Runs, Failed, LoopLimit, PromptTokens, CompletionTokens, CostUsd,
                   ToolCalls, ToolErrors, Denied, Staged
            FROM RunDaily
            WHERE Day >= @from AND Day <= @to
              AND (@agent IS NULL OR AgentId = @agent COLLATE NOCASE)
              AND (@unit IS NULL OR UnitId = @unit COLLATE NOCASE)
            ORDER BY Day, AgentId
            """;
        cmd.Parameters.AddWithValue("@from", from.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture));
        cmd.Parameters.AddWithValue("@to", to.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture));
        cmd.Parameters.AddWithValue("@agent", (object?)agentId ?? DBNull.Value);
        cmd.Parameters.AddWithValue("@unit", (object?)unitId ?? DBNull.Value);
        var result = new List<RunDay>();
        await using var r = await cmd.ExecuteReaderAsync(ct);
        while (await r.ReadAsync(ct))
            result.Add(new RunDay(r.GetString(0), r.GetString(1), r.GetString(2), r.GetInt32(3), r.GetInt32(4), r.GetInt32(5),
                r.GetInt64(6), r.GetInt64(7),
                decimal.TryParse(r.GetString(8), NumberStyles.Any, CultureInfo.InvariantCulture, out var c) ? c : 0m,
                r.GetInt32(9), r.GetInt32(10), r.GetInt32(11), r.GetInt32(12)));
        return result;
    }

    // ─── Moving to the archive ───

    /// <summary>
    /// Moves audit rows and receipts older than the hot window into their month's archive file.
    /// Days are condensed first, so no day value is lost with the move. Copy and delete happen
    /// in one transaction: a row is in one place or the other, never in none.
    /// </summary>
    public async Task<int> ArchiveAsync(CancellationToken ct)
    {
        var hotDays = settings().HotDays;
        if (hotDays <= 0)
            return 0;
        await CondenseAsync(ct);

        // Whole days only, and never today's or yesterday's: those are not condensed for good yet.
        var cutoff = Now.Date.AddDays(-Math.Max(2, hotDays)).ToString("O");
        System.IO.Directory.CreateDirectory(Directory);

        return await storage.WriteAsync(async conn =>
        {
            var months = new SortedSet<string>(StringComparer.Ordinal);
            foreach (var table in new[] { "AuditLog", "RunReceipts" })
            {
                using var cmd = conn.CreateCommand();
                cmd.CommandText = $"SELECT DISTINCT substr(OccurredAt, 1, 7) FROM {table} WHERE OccurredAt < @cutoff";
                cmd.Parameters.AddWithValue("@cutoff", cutoff);
                await using var r = await cmd.ExecuteReaderAsync(ct);
                while (await r.ReadAsync(ct))
                    months.Add(r.GetString(0));
            }

            var moved = 0;
            foreach (var month in months)
                moved += await MoveMonthAsync(conn, month, cutoff, ct);
            if (moved > 0)
                logger.LogInformation("Audit archive: {Count} row(s) older than {Days} days moved to {Folder}", moved, hotDays, Directory);
            return moved;
        }, ct);
    }

    private async Task<int> MoveMonthAsync(SqliteConnection conn, string month, string cutoff, CancellationToken ct)
    {
        var file = Path.Combine(Directory, FileNameOf(month));
        using (var attach = conn.CreateCommand())
        {
            attach.CommandText = "ATTACH DATABASE @file AS arch";
            attach.Parameters.AddWithValue("@file", file);
            await attach.ExecuteNonQueryAsync(ct);
        }
        try
        {
            using (var create = conn.CreateCommand())
            {
                // Same columns as the working tables, row ids kept — an id in a report still finds its row.
                create.CommandText = """
                    CREATE TABLE IF NOT EXISTS arch.AuditLog AS SELECT * FROM main.AuditLog WHERE 0;
                    CREATE TABLE IF NOT EXISTS arch.RunReceipts AS SELECT * FROM main.RunReceipts WHERE 0;
                    CREATE INDEX IF NOT EXISTS arch.IX_Archive_AuditLog_Run ON AuditLog (RunId);
                    CREATE INDEX IF NOT EXISTS arch.IX_Archive_RunReceipts_Run ON RunReceipts (RunId);
                    CREATE INDEX IF NOT EXISTS arch.IX_Archive_RunReceipts_Task ON RunReceipts (TaskId);
                    """;
                await create.ExecuteNonQueryAsync(ct);
            }

            // A column the working table gained after the archive file was made is added to it —
            // otherwise the month's next move would fail on a column count.
            var columns = new Dictionary<string, IReadOnlyList<string>>();
            foreach (var table in new[] { "AuditLog", "RunReceipts" })
                columns[table] = await AlignColumnsAsync(conn, table, ct);

            await using var tx = await conn.BeginTransactionAsync(ct);
            var moved = 0;
            foreach (var table in new[] { "AuditLog", "RunReceipts" })
            {
                var list = string.Join(", ", columns[table]);
                using var copy = conn.CreateCommand();
                copy.Transaction = (SqliteTransaction)tx;
                copy.CommandText = $"""
                    INSERT INTO arch.{table} ({list}) SELECT {list} FROM main.{table}
                    WHERE OccurredAt < @cutoff AND substr(OccurredAt, 1, 7) = @month
                      AND Id NOT IN (SELECT Id FROM arch.{table});
                    DELETE FROM main.{table} WHERE OccurredAt < @cutoff AND substr(OccurredAt, 1, 7) = @month
                      AND Id IN (SELECT Id FROM arch.{table});
                    """;
                copy.Parameters.AddWithValue("@cutoff", cutoff);
                copy.Parameters.AddWithValue("@month", month);
                moved += await copy.ExecuteNonQueryAsync(ct) / 2;
            }
            await tx.CommitAsync(ct);
            return moved;
        }
        finally
        {
            using var detach = conn.CreateCommand();
            detach.CommandText = "DETACH DATABASE arch";
            await detach.ExecuteNonQueryAsync(CancellationToken.None);
        }
    }

    /// <summary>The working table's columns, each present in the archive table too.</summary>
    private static async Task<IReadOnlyList<string>> AlignColumnsAsync(SqliteConnection conn, string table, CancellationToken ct)
    {
        async Task<List<(string Name, string Type)>> Columns(string schema)
        {
            using var cmd = conn.CreateCommand();
            cmd.CommandText = $"SELECT name, type FROM pragma_table_info('{table}', '{schema}')";
            var list = new List<(string, string)>();
            await using var r = await cmd.ExecuteReaderAsync(ct);
            while (await r.ReadAsync(ct))
                list.Add((r.GetString(0), r.GetString(1)));
            return list;
        }

        var main = await Columns("main");
        var archived = (await Columns("arch")).Select(c => c.Name).ToHashSet(StringComparer.OrdinalIgnoreCase);
        foreach (var (name, type) in main.Where(c => !archived.Contains(c.Name)))
        {
            using var add = conn.CreateCommand();
            add.CommandText = $"ALTER TABLE arch.{table} ADD COLUMN {name} {type}";
            await add.ExecuteNonQueryAsync(ct);
        }
        return main.Select(c => c.Name).ToList();
    }

    /// <summary>The archive files, newest month first.</summary>
    public IReadOnlyList<AuditArchiveFile> Files() => FilesIn(Directory);

    private readonly CancellationTokenSource _cts = new();
    private Task? _loop;

    /// <summary>Condenses and archives once after the start, then every six hours.</summary>
    public void Start() => _loop ??= LoopAsync(_cts.Token);

    private async Task LoopAsync(CancellationToken ct)
    {
        try { await Task.Delay(TimeSpan.FromMinutes(2), ct); }
        catch (OperationCanceledException) { return; }

        while (!ct.IsCancellationRequested)
        {
            try
            {
                await ArchiveAsync(ct);
                if (settings().HotDays <= 0)
                    await CondenseAsync(ct);
            }
            catch (Exception ex) when (ex is not OperationCanceledException)
            {
                logger.LogWarning(ex, "Audit archive: condensing or moving failed");
            }

            try { await Task.Delay(TimeSpan.FromHours(6), ct); }
            catch (OperationCanceledException) { return; }
        }
    }

    public async ValueTask DisposeAsync()
    {
        await _cts.CancelAsync();
        if (_loop is not null)
        {
            try { await _loop; }
            catch (OperationCanceledException) { }
        }
        _cts.Dispose();
    }

    public static IReadOnlyList<AuditArchiveFile> FilesIn(string directory)
    {
        if (!System.IO.Directory.Exists(directory))
            return [];
        return System.IO.Directory.EnumerateFiles(directory, "audit-????-??.db")
            .Select(f => new AuditArchiveFile(Path.GetFileNameWithoutExtension(f)["audit-".Length..], Path.GetFileName(f), new FileInfo(f).Length))
            .OrderByDescending(f => f.Month, StringComparer.Ordinal)
            .ToList();
    }
}