using Dapper;
using Microsoft.Extensions.Logging;
using StellaOps.Messaging.Abstractions;

namespace StellaOps.Messaging.Transport.Postgres;

/// <summary>
/// PostgreSQL implementation of <see cref="IIdempotencyStore"/>.
/// Uses INSERT ... ON CONFLICT DO NOTHING for atomic claiming.
/// </summary>
public sealed class PostgresIdempotencyStore : IIdempotencyStore
{
    private readonly PostgresConnectionFactory _connectionFactory;
    private readonly string _name;
    private readonly ILogger<PostgresIdempotencyStore>? _logger;
    private readonly TimeProvider _timeProvider;
    private bool _tableInitialized;

    public PostgresIdempotencyStore(
        PostgresConnectionFactory connectionFactory,
        string name,
        ILogger<PostgresIdempotencyStore>? logger = null,
        TimeProvider? timeProvider = null)
    {
        _connectionFactory = connectionFactory ?? throw new ArgumentNullException(nameof(connectionFactory));
        _name = name ?? throw new ArgumentNullException(nameof(name));
        _logger = logger;
        _timeProvider = timeProvider ?? TimeProvider.System;
    }

    /// <inheritdoc />
    public string ProviderName => "postgres";

    private string TableName => $"{_connectionFactory.Schema}.idempotency_{_name.ToLowerInvariant().Replace("-", "_")}";

    /// <inheritdoc />
    public async ValueTask<IdempotencyResult> TryClaimAsync(
        string key,
        string value,
        TimeSpan window,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);
        ArgumentNullException.ThrowIfNull(value);

        await EnsureTableExistsAsync(cancellationToken).ConfigureAwait(false);

        await using var conn = await _connectionFactory.OpenConnectionAsync(cancellationToken).ConfigureAwait(false);

        var now = _timeProvider.GetUtcNow();
        var expiresAt = now.Add(window);

        // Clean up expired entries first
        var cleanupSql = $@"DELETE FROM {TableName} WHERE expires_at < @Now";
        await conn.ExecuteAsync(new CommandDefinition(cleanupSql, new { Now = now.UtcDateTime }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);

        // Try to insert
        var sql = $@"
            INSERT INTO {TableName} (key, value, expires_at)
            VALUES (@Key, @Value, @ExpiresAt)
            ON CONFLICT (key) DO NOTHING
            RETURNING TRUE";

        var result = await conn.ExecuteScalarAsync<bool?>(
            new CommandDefinition(sql, new { Key = key, Value = value, ExpiresAt = expiresAt.UtcDateTime }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);

        if (result == true)
        {
            return IdempotencyResult.Claimed();
        }

        // Key already exists, get existing value
        var existingSql = $@"SELECT value FROM {TableName} WHERE key = @Key";
        var existingValue = await conn.ExecuteScalarAsync<string?>(
            new CommandDefinition(existingSql, new { Key = key }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);

        return IdempotencyResult.Duplicate(existingValue ?? string.Empty);
    }

    /// <inheritdoc />
    public async ValueTask<bool> ExistsAsync(string key, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);

        await EnsureTableExistsAsync(cancellationToken).ConfigureAwait(false);

        await using var conn = await _connectionFactory.OpenConnectionAsync(cancellationToken).ConfigureAwait(false);

        var now = _timeProvider.GetUtcNow();
        var sql = $@"SELECT EXISTS(SELECT 1 FROM {TableName} WHERE key = @Key AND expires_at > @Now)";

        return await conn.ExecuteScalarAsync<bool>(
            new CommandDefinition(sql, new { Key = key, Now = now.UtcDateTime }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);
    }

    /// <inheritdoc />
    public async ValueTask<string?> GetAsync(string key, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);

        await EnsureTableExistsAsync(cancellationToken).ConfigureAwait(false);

        await using var conn = await _connectionFactory.OpenConnectionAsync(cancellationToken).ConfigureAwait(false);

        var now = _timeProvider.GetUtcNow();
        var sql = $@"SELECT value FROM {TableName} WHERE key = @Key AND expires_at > @Now";

        return await conn.ExecuteScalarAsync<string?>(
            new CommandDefinition(sql, new { Key = key, Now = now.UtcDateTime }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);
    }

    /// <inheritdoc />
    public async ValueTask<bool> ReleaseAsync(string key, CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);

        await EnsureTableExistsAsync(cancellationToken).ConfigureAwait(false);

        await using var conn = await _connectionFactory.OpenConnectionAsync(cancellationToken).ConfigureAwait(false);

        var sql = $@"DELETE FROM {TableName} WHERE key = @Key";
        var deleted = await conn.ExecuteAsync(
            new CommandDefinition(sql, new { Key = key }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);

        return deleted > 0;
    }

    /// <inheritdoc />
    public async ValueTask<bool> ExtendAsync(
        string key,
        TimeSpan extension,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(key);

        await EnsureTableExistsAsync(cancellationToken).ConfigureAwait(false);

        await using var conn = await _connectionFactory.OpenConnectionAsync(cancellationToken).ConfigureAwait(false);

        var sql = $@"
            UPDATE {TableName}
            SET expires_at = expires_at + @Extension
            WHERE key = @Key";

        var updated = await conn.ExecuteAsync(
            new CommandDefinition(sql, new { Key = key, Extension = extension }, cancellationToken: cancellationToken))
            .ConfigureAwait(false);

        return updated > 0;
    }

    private async ValueTask EnsureTableExistsAsync(CancellationToken cancellationToken)
    {
        if (_tableInitialized) return;

        await using var conn = await _connectionFactory.OpenConnectionAsync(cancellationToken).ConfigureAwait(false);

        var safeName = _name.ToLowerInvariant().Replace("-", "_");
        var sql = $@"
            CREATE TABLE IF NOT EXISTS {TableName} (
                key TEXT PRIMARY KEY,
                value TEXT NOT NULL,
                expires_at TIMESTAMPTZ NOT NULL
            );
            CREATE INDEX IF NOT EXISTS idx_{safeName}_expires ON {TableName} (expires_at);";

        await conn.ExecuteAsync(new CommandDefinition(sql, cancellationToken: cancellationToken)).ConfigureAwait(false);
        _tableInitialized = true;
    }
}

/// <summary>
/// Factory for creating PostgreSQL idempotency store instances.
/// </summary>
public sealed class PostgresIdempotencyStoreFactory : IIdempotencyStoreFactory
{
    private readonly PostgresConnectionFactory _connectionFactory;
    private readonly ILoggerFactory? _loggerFactory;
    private readonly TimeProvider _timeProvider;

    public PostgresIdempotencyStoreFactory(
        PostgresConnectionFactory connectionFactory,
        ILoggerFactory? loggerFactory = null,
        TimeProvider? timeProvider = null)
    {
        _connectionFactory = connectionFactory ?? throw new ArgumentNullException(nameof(connectionFactory));
        _loggerFactory = loggerFactory;
        _timeProvider = timeProvider ?? TimeProvider.System;
    }

    /// <inheritdoc />
    public string ProviderName => "postgres";

    /// <inheritdoc />
    public IIdempotencyStore Create(string name)
    {
        ArgumentNullException.ThrowIfNull(name);
        return new PostgresIdempotencyStore(
            _connectionFactory,
            name,
            _loggerFactory?.CreateLogger<PostgresIdempotencyStore>(),
            _timeProvider);
    }
}