using System.Text;

namespace SQLInsight.Core.DynamicsAx;

/// <summary>
/// The optional read access to AX tables. The agent normally reads only metadata (grant-least-privilege.sql); the AX
/// data checks need SELECT on a few AX system tables (batch jobs, number sequences, RecId allocation, companies), and
/// the customer decides whether to give it, per database. No customer data tables, never more than SELECT.
/// db/permissions/grant-dynamics-ax-read.sql does the same for any database; <see cref="GrantSql"/> makes the exact
/// statements for one database, with its schema (bmssa in AX 3.0) and the agent's login filled in.
/// </summary>
public static class AxReadAccess
{
    public const string ScriptPath = "db/permissions/grant-dynamics-ax-read.sql";

    public const string RevokeScriptPath = "db/permissions/revoke-dynamics-ax-read.sql";

    /// <summary>Used in the GRANT text when the agent's login is not known yet.</summary>
    public const string LoginPlaceholder = @"DOMÆNE\svc-sqlinsight$";

    /// <summary>The tables the read access covers for a version (those that exist in the database).</summary>
    public static IReadOnlyList<string> Tables(AxDatabase database)
    {
        ArgumentNullException.ThrowIfNull(database);
        return AxSchemaAdapter.For(database.Version) is { } adapter
            ? adapter.ReadTables.Where(database.HasTable).ToList()
            : [];
    }

    /// <summary>The tables the agent may not read yet.</summary>
    public static IReadOnlyList<string> Missing(AxDatabase database) => Tables(database).Where(t => !database.CanRead(t)).ToList();

    /// <summary>
    /// The exact statements that give the agent SELECT on <paramref name="tables"/> (all the version's tables when null)
    /// in this database. Run by a sysadmin or db_owner; SQLInsight never runs it.
    /// </summary>
    public static string GrantSql(AxDatabase database, string? login, IEnumerable<string>? tables = null)
    {
        ArgumentNullException.ThrowIfNull(database);
        login = string.IsNullOrWhiteSpace(login) ? LoginPlaceholder : login.Trim();
        var user = database.DatabaseUser ?? login;
        var sql = new StringBuilder()
            .Append("USE ").Append(AxSql.Identifier(database.Database)).Append(";\r\n");
        if (database.DatabaseUser is null)
        {
            sql.Append("IF NOT EXISTS (SELECT 1 FROM sys.database_principals WHERE sid = SUSER_SID(").Append(AxSql.Literal(login)).Append("))\r\n")
                .Append("    CREATE USER ").Append(AxSql.Identifier(login)).Append(" FOR LOGIN ").Append(AxSql.Identifier(login)).Append(";\r\n");
        }

        foreach (var table in (tables ?? Tables(database)).Distinct(StringComparer.OrdinalIgnoreCase))
        {
            sql.Append("GRANT SELECT ON ").Append(database.Qualified(table)).Append(" TO ").Append(AxSql.Identifier(user)).Append(";\r\n");
        }

        return sql.ToString();
    }

    /// <summary>db/permissions/grant-dynamics-ax-read.sql as shipped.</summary>
    public static string Template()
    {
        using var stream = typeof(AxReadAccess).Assembly.GetManifestResourceStream("SQLInsight.Core.grant-dynamics-ax-read.sql")
            ?? throw new InvalidOperationException("grant-dynamics-ax-read.sql mangler i programmet.");
        using var reader = new StreamReader(stream);
        return reader.ReadToEnd();
    }

    /// <summary>The shipped script with the database and the agent's login filled in.</summary>
    public static string Script(string database, string? login)
    {
        ArgumentNullException.ThrowIfNull(database);
        return Template()
            .Replace("SET @DatabaseName = N'AXDB';", "SET @DatabaseName = " + AxSql.Literal(database) + ";", StringComparison.Ordinal)
            .Replace("SET @LoginName = N'" + LoginPlaceholder + "';", "SET @LoginName = " + AxSql.Literal(string.IsNullOrWhiteSpace(login) ? LoginPlaceholder : login.Trim()) + ";",
                StringComparison.Ordinal);
    }

    /// <summary>"Ikke målbar" for a check that needs <paramref name="tables"/>, with the exact GRANT text.</summary>
    public static string NotMeasurable(AxDatabase database, IReadOnlyList<string> tables, string? login = null)
    {
        ArgumentNullException.ThrowIfNull(database);
        ArgumentNullException.ThrowIfNull(tables);
        return $"Ikke målbar: agenten må ikke læse {string.Join(", ", tables.Select(t => database.Schema + "." + t))} i {database.Database} "
            + $"(valgfri AX-læseadgang). Kør som sysadmin eller db_owner: {GrantSql(database, login ?? database.AgentLogin, tables).Replace("\r\n", " ", StringComparison.Ordinal).Trim()}";
    }
}