using System.IO;
using System.Text;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.S7.SymbolImport;

namespace ZB.MOM.WW.OtOpcUa.Driver.S7.Tests.SymbolImport;

/// <summary>
///     Unit coverage for <see cref="AwlImporter"/>. The AWL grammar is best-effort
///     position-based; these tests pin the assignment rules so a regression in offset
///     accounting surfaces immediately.
/// </summary>
[Trait("Category", "Unit")]
public sealed class AwlImporterTests
{
    private static S7ImportResult ParseString(string awl, S7ImportOptions? opts = null)
    {
        var importer = new AwlImporter(NullLogger<AwlImporter>.Instance);
        using var stream = new MemoryStream(Encoding.UTF8.GetBytes(awl));
        return importer.Parse(stream, opts);
    }

    [Fact]
    public void Parse_var_global_three_ints_yields_sequential_MW_addresses()
    {
        const string awl = """
            VAR_GLOBAL
              Speed : INT;
              Pressure : INT;
              Level : INT;
            END_VAR
            """;
        var result = ParseString(awl);
        result.ParsedCount.ShouldBe(3);
        result.Tags.Count.ShouldBe(3);

        result.Tags[0].Name.ShouldBe("Speed");
        result.Tags[0].Address.ShouldBe("MW0");
        result.Tags[0].DataType.ShouldBe(S7DataType.Int16);

        result.Tags[1].Name.ShouldBe("Pressure");
        result.Tags[1].Address.ShouldBe("MW2");

        result.Tags[2].Name.ShouldBe("Level");
        result.Tags[2].Address.ShouldBe("MW4");
    }

    [Fact]
    public void Parse_data_block_mixed_int_real_yields_db_prefixed_addresses()
    {
        const string awl = """
            DATA_BLOCK DB1
              STRUCT
                CycleCount : INT;
                Setpoint : REAL;
                ActualValue : REAL;
              END_STRUCT;
            BEGIN
            END_DATA_BLOCK
            """;
        var result = ParseString(awl);
        result.ParsedCount.ShouldBe(3);

        result.Tags[0].Name.ShouldBe("CycleCount");
        result.Tags[0].Address.ShouldBe("DB1.DBW0");
        result.Tags[0].DataType.ShouldBe(S7DataType.Int16);

        result.Tags[1].Name.ShouldBe("Setpoint");
        result.Tags[1].Address.ShouldBe("DB1.DBD2");
        result.Tags[1].DataType.ShouldBe(S7DataType.Float32);

        result.Tags[2].Name.ShouldBe("ActualValue");
        result.Tags[2].Address.ShouldBe("DB1.DBD6");
        result.Tags[2].DataType.ShouldBe(S7DataType.Float32);
    }

    [Fact]
    public void Parse_strips_block_and_line_comments()
    {
        const string awl = """
            (* Block comment — ignored *)
            VAR_GLOBAL
              // Line comment — ignored
              Counter : INT;  // inline comment after the decl
              (* another (* faux-nested *) block — non-nesting matcher should still consume it *)
              Velocity : REAL;
            END_VAR
            """;
        var result = ParseString(awl);
        // Block-comment regex is non-greedy; "another " up to first "*)" is one comment, the rest
        // becomes part of the body but the regex extracts the two valid declarations cleanly.
        result.ParsedCount.ShouldBeGreaterThanOrEqualTo(2);
        result.Tags.ShouldContain(t => t.Name == "Counter" && t.DataType == S7DataType.Int16);
        result.Tags.ShouldContain(t => t.Name == "Velocity" && t.DataType == S7DataType.Float32);
    }

    [Fact]
    public void Parse_empty_body_returns_empty_result()
    {
        var result = ParseString(string.Empty);
        result.ParsedCount.ShouldBe(0);
        result.Tags.ShouldBeEmpty();
    }

    [Fact]
    public void Parse_var_global_with_initial_values_strips_init_clause()
    {
        const string awl = """
            VAR_GLOBAL
              SetVal : INT := 42;
              Threshold : REAL := 3.14;
            END_VAR
            """;
        var result = ParseString(awl);
        result.ParsedCount.ShouldBe(2);
        result.Tags[0].DataType.ShouldBe(S7DataType.Int16);
        result.Tags[1].DataType.ShouldBe(S7DataType.Float32);
    }

    [Fact]
    public void Parse_udt_typed_decl_imports_as_placeholder()
    {
        const string awl = """
            DATA_BLOCK DB5
              STRUCT
                Cfg : "MyConfig";
                Flag : BOOL;
              END_STRUCT;
            BEGIN
            END_DATA_BLOCK
            """;
        var result = ParseString(awl);
        result.ParsedCount.ShouldBe(2);
        result.UdtPlaceholderCount.ShouldBe(1);
        var placeholder = result.Tags.First(t => t.Name == "Cfg");
        placeholder.DataType.ShouldBe(S7DataType.Byte);
        placeholder.Writable.ShouldBeFalse();
    }

    [Fact]
    public void Parse_string_with_length_uses_n_plus_2_byte_layout()
    {
        const string awl = """
            DATA_BLOCK DB7
              STRUCT
                FirstByte : BYTE;
                Recipe : STRING[80];
                Trailing : INT;
              END_STRUCT;
            BEGIN
            END_DATA_BLOCK
            """;
        var result = ParseString(awl);
        result.ParsedCount.ShouldBe(3);
        // Recipe (STRING[80]) consumes 82 bytes starting at offset 1 (rounded to 2 = 2);
        // trailing INT lands at 84.
        var first = result.Tags.First(t => t.Name == "FirstByte");
        first.Address.ShouldBe("DB7.DBB0");
        var trailing = result.Tags.First(t => t.Name == "Trailing");
        trailing.Address.ShouldBe("DB7.DBW84");
    }

    [Fact]
    public void StripComments_removes_block_and_line_comments()
    {
        var input = "VAR_GLOBAL (* hi *)\nA : INT; // trailing\nEND_VAR";
        var stripped = AwlImporter.StripComments(input);
        stripped.ShouldNotContain("(*");
        stripped.ShouldNotContain("*)");
        stripped.ShouldNotContain("//");
        stripped.ShouldContain("A : INT;");
    }

    [Fact]
    public void ResolveType_maps_primitive_step7_types_correctly()
    {
        AwlImporter.ResolveType("INT").S7Type.ShouldBe(S7DataType.Int16);
        AwlImporter.ResolveType("REAL").S7Type.ShouldBe(S7DataType.Float32);
        AwlImporter.ResolveType("LREAL").S7Type.ShouldBe(S7DataType.Float64);
        AwlImporter.ResolveType("BOOL").S7Type.ShouldBe(S7DataType.Bool);
        AwlImporter.ResolveType("DINT").S7Type.ShouldBe(S7DataType.Int32);
        AwlImporter.ResolveType("STRING[20]").S7Type.ShouldBe(S7DataType.String);
        AwlImporter.ResolveType("STRING[20]").SizeBytes.ShouldBe(22);
        AwlImporter.ResolveType("STRUCT").IsUdt.ShouldBeTrue();
        AwlImporter.ResolveType("\"MyType\"").IsUdt.ShouldBeTrue();
    }

    [Fact]
    public void AlignTo_rounds_word_offsets_up_to_word_boundary()
    {
        AwlImporter.AlignTo(0, 2).ShouldBe(0);
        AwlImporter.AlignTo(1, 2).ShouldBe(2);
        AwlImporter.AlignTo(3, 2).ShouldBe(4);
        AwlImporter.AlignTo(2, 4).ShouldBe(2); // 2-byte alignment is the cap
        AwlImporter.AlignTo(0, 1).ShouldBe(0); // bytes don't need alignment
    }

    [Fact]
    public void ExtractDbNumber_pulls_db_number_from_header()
    {
        AwlImporter.ExtractDbNumber(" DB1").ShouldBe(1);
        AwlImporter.ExtractDbNumber(" DB42 \"Name\"").ShouldBe(42);
        AwlImporter.ExtractDbNumber("\"NameOnly\"").ShouldBeNull();
    }

    [Fact]
    public void Parse_max_rows_caps_imports()
    {
        const string awl = """
            VAR_GLOBAL
              A : INT;
              B : INT;
              C : INT;
              D : INT;
            END_VAR
            """;
        var result = ParseString(awl, new S7ImportOptions(MaxRowsToImport: 2));
        result.ParsedCount.ShouldBe(2);
    }
}