using System.Data.Common;
using Microsoft.Data.Sqlite;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Types;
using ZB.MOM.WW.ScadaBridge.InboundAPI;
using Xunit;

namespace ZB.MOM.WW.ScadaBridge.InboundAPI.Tests;

public class InboundDatabaseHelperTests
{
    private sealed class SqliteGateway : IDatabaseGateway
    {
        private readonly string _cs;
        // Test seam: When false the open ignores the passed token, so a
        // pre-cancelled token surfaces at Execute/Read (not at open) — letting a test
        // prove the EXECUTE path honours the deadline token, not just the open.
        private readonly bool _honorTokenOnOpen;
        /// <summary>
        /// Initializes a new instance of the <c>SqliteGateway</c> class.
        /// </summary>
        /// <param name="cs">The cs.</param>
        /// <param name="honorTokenOnOpen">The honor token on open.</param>
        public SqliteGateway(string cs, bool honorTokenOnOpen = true)
        { _cs = cs; _honorTokenOnOpen = honorTokenOnOpen; }
        /// <inheritdoc />
        public async Task<DbConnection> GetConnectionAsync(string name, CancellationToken ct = default)
        { var c = new SqliteConnection(_cs); await c.OpenAsync(_honorTokenOnOpen ? ct : CancellationToken.None); return c; }
        /// <inheritdoc />
        public Task<ExternalCallResult> CachedWriteAsync(string c, string s,
            IReadOnlyDictionary<string, object?>? p = null, string? o = null, CancellationToken ct = default,
            TrackedOperationId? t = null, Guid? e = null, string? src = null, Guid? pe = null)
            => throw new NotImplementedException();
    }

    private static SqliteGateway SeededGateway(bool honorTokenOnOpen = true)
    {
        var keep = new SqliteConnection("DataSource=file:movein?mode=memory&cache=shared");
        keep.Open(); // keep-alive: shared in-memory db lives until process exit
        using var cmd = keep.CreateCommand();
        cmd.CommandText = "CREATE TABLE IF NOT EXISTS Machine(Code TEXT, SAPID TEXT); DELETE FROM Machine; INSERT INTO Machine VALUES('Z28061A','131453');";
        cmd.ExecuteNonQuery();
        return new SqliteGateway("DataSource=file:movein?mode=memory&cache=shared", honorTokenOnOpen);
    }

    /// <summary>Verifies that query single async returns first column with bound parameter.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QuerySingleAsync_returns_first_column_with_bound_parameter()
    {
        var helper = new InboundDatabaseHelper(SeededGateway(), CancellationToken.None);
        var code = await helper.QuerySingleAsync<string>("BTDB", "SELECT Code FROM Machine WHERE SAPID=@s", new { s = "131453" });
        Assert.Equal("Z28061A", code);
    }

    /// <summary>Verifies that query single async returns default when no rows.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QuerySingleAsync_returns_default_when_no_rows()
    {
        var helper = new InboundDatabaseHelper(SeededGateway(), CancellationToken.None);
        var code = await helper.QuerySingleAsync<string>("BTDB", "SELECT Code FROM Machine WHERE SAPID=@s", new { s = "999999" });
        Assert.Null(code);
    }

    /// <summary>Verifies that query async returns row with case insensitive keys.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QueryAsync_returns_row_with_case_insensitive_keys()
    {
        var helper = new InboundDatabaseHelper(SeededGateway(), CancellationToken.None);
        var rows = await helper.QueryAsync("BTDB", "SELECT Code, SAPID FROM Machine WHERE SAPID=@s", new { s = "131453" });
        Assert.Single(rows);
        var row = rows[0];
        Assert.Equal("Z28061A", row["code"]);
        Assert.Equal("Z28061A", row["CODE"]);
    }

    /// <summary>Verifies that query async returns empty list when no rows match.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QueryAsync_returns_empty_list_when_no_rows_match()
    {
        var helper = new InboundDatabaseHelper(SeededGateway(), CancellationToken.None);
        var rows = await helper.QueryAsync("BTDB", "SELECT Code, SAPID FROM Machine WHERE SAPID=@s", new { s = "999999" });
        Assert.Empty(rows);
    }

    // --- Writes are permitted (design decision) ---

    /// <summary>Verifies that execute async performs write and returns rows affected.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task ExecuteAsync_performs_write_and_returns_rows_affected()
    {
        var helper = new InboundDatabaseHelper(SeededGateway(), CancellationToken.None);
        var affected = await helper.ExecuteAsync(
            "BTDB", "UPDATE Machine SET Code=@c WHERE SAPID=@s", new { c = "UPDATED", s = "131453" });
        Assert.Equal(1, affected);

        // The write actually landed (read it back through the same helper).
        var code = await helper.QuerySingleAsync<string>("BTDB", "SELECT Code FROM Machine WHERE SAPID=@s", new { s = "131453" });
        Assert.Equal("UPDATED", code);
    }

    // --- SQL-injection protection — values are bound, not concatenated ---

    /// <summary>Verifies that parameter values are bound not concatenated.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task ParameterValues_are_bound_not_concatenated()
    {
        // A classic injection payload as the parameter VALUE. If the helper concatenated
        // it, "WHERE SAPID='131453' OR '1'='1'" would match the seeded row and return
        // "Z28061A". Because the value is bound as a literal parameter, it matches no
        // SAPID and the query returns null — proving the value never altered the SQL.
        var helper = new InboundDatabaseHelper(SeededGateway(), CancellationToken.None);
        var code = await helper.QuerySingleAsync<string>(
            "BTDB", "SELECT Code FROM Machine WHERE SAPID=@s", new { s = "131453' OR '1'='1" });
        Assert.Null(code);
    }

    // --- Negative paths ---

    /// <summary>Verifies that query single async null gateway throws.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QuerySingleAsync_null_gateway_throws()
    {
        var helper = new InboundDatabaseHelper(gateway: null, CancellationToken.None);
        await Assert.ThrowsAsync<InvalidOperationException>(
            () => helper.QuerySingleAsync<string>("BTDB", "SELECT 1"));
    }

    /// <summary>Verifies that query async null gateway throws.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QueryAsync_null_gateway_throws()
    {
        var helper = new InboundDatabaseHelper(gateway: null, CancellationToken.None);
        await Assert.ThrowsAsync<InvalidOperationException>(
            () => helper.QueryAsync("BTDB", "SELECT 1"));
    }

    /// <summary>Verifies that execute async null gateway throws.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task ExecuteAsync_null_gateway_throws()
    {
        var helper = new InboundDatabaseHelper(gateway: null, CancellationToken.None);
        await Assert.ThrowsAsync<InvalidOperationException>(
            () => helper.ExecuteAsync("BTDB", "DELETE FROM Machine"));
    }

    // --- The method-deadline token bounds the query on the EXECUTE path ---

    /// <summary>Verifies that query single async honours cancellation token on execute.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task QuerySingleAsync_honours_cancellation_token_on_execute()
    {
        // The gateway opens with None (so the open succeeds), but the helper forwards the
        // pre-cancelled deadline token to ExecuteScalarAsync — which must observe it. This
        // proves the fix threads the token past the connection open, where the old
        // synchronous ExecuteScalar() ignored cancellation entirely.
        using var cts = new CancellationTokenSource();
        await cts.CancelAsync();
        var helper = new InboundDatabaseHelper(SeededGateway(honorTokenOnOpen: false), cts.Token);
        await Assert.ThrowsAnyAsync<OperationCanceledException>(
            () => helper.QuerySingleAsync<string>("BTDB", "SELECT Code FROM Machine"));
    }
}