using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.RegularExpressions;

internal static class SqlCmdScriptParser

{

    private static readonly Command[] ControlCommands =

    {

        new()

        {

            Id = "setvar",

            Pattern = new(@":(?<command>setvar)\s+(?<name>\w+)\s+""(?<value>.*)"""),

            IsFullLine = true,

            MatchSubstitution =

                (match, variables) =>

                {

                    variables.Add(match.Groups["name"].Value, match.Groups["value"].Value);

                    return string.Empty;

                },

        },

        new()

        {

            Id = "on error",

            Pattern = new(@":(?<command>on error)\s+(?<value>exit|ignore)"),

            IsFullLine = true,

            MatchSubstitution = (_, _) => string.Empty,

        },

        new()

        {

            Id = "$",

            Pattern = new(@"(?<command>\$)\((?<name>\w+)\)"),

            IsFullLine = false,

            MatchSubstitution =

                (match, variables) =>

                    variables.GetValueOrDefault(match.Groups["name"].Value) ?? string.Empty,

        },

    };

​

    private static readonly IReadOnlyDictionary<string, Command> ControlCommandsMap =

        ControlCommands.ToDictionary(c => c.Id, StringComparer.OrdinalIgnoreCase);

​

    private static readonly Regex ControlCommandsPattern = GetControlCommandsPattern();

​

    private static readonly Regex BatchSeparatorPattern = new Regex("GO").ToFullLine();

​

    public static IReadOnlyCollection<string> Parse(

        string input, IReadOnlyDictionary<string, string> variables = null) =>

        input

            .SubstituteControlCommands(variables)

            .SplitBatch();

​

    private static Regex GetControlCommandsPattern()

    {

        var patterns = ControlCommands

            .Select(c => c.IsFullLine ? c.Pattern.ToFullLine() : c.Pattern)

            .Select(p => $"({p})")

            .ToList();

        var combinedPattern = string.Join("|", patterns);

        return new Regex(combinedPattern, RegexOptions.Multiline | RegexOptions.Compiled);

    }

​

    private static Regex ToFullLine(this Regex source) =>

        new($@"^\s*{source}\s*$\n?", RegexOptions.Multiline | RegexOptions.Compiled);

​

    private static string SubstituteControlCommands(

        this string input, IReadOnlyDictionary<string, string> variables)

    {

        var establishedVariables = new Dictionary<string, string>(

            variables ?? new Dictionary<string, string>(), StringComparer.OrdinalIgnoreCase);

        return ControlCommandsPattern

            .Replace(input, match => SubstituteControlCommandMatch(match, establishedVariables));

    }

​

    private static string SubstituteControlCommandMatch(

        Match match, Dictionary<string, string> variables)

    {

        var commandId = match.Groups["command"].Value;

        var command = ControlCommandsMap.GetValueOrDefault(commandId)

            ?? throw new InvalidOperationException($"Unknown command: {commandId}");

        return command.MatchSubstitution(match, variables);

    }

​

    private static IReadOnlyCollection<string> SplitBatch(this string input) =>

        BatchSeparatorPattern.Split(input)

            .Where(s => !string.IsNullOrEmpty(s))

            .ToList();

​

    private sealed class Command

    {

        public string Id { get; init; } = string.Empty;

​

        public Regex Pattern { get; init; } = new(string.Empty);

​

        public bool IsFullLine { get; init; }

​

        public Func<Match, Dictionary<string, string>, string> MatchSubstitution { get; init; } =

            (_, _) => string.Empty;

    }

}

​

public static class Program

{

    public static void Main()

    {

        var inputScript =

            """

            /*

            Deployment script for MessageQueue

            This code was generated by a tool.

            Changes to this file may cause incorrect behavior and will be lost if

            the code is regenerated.

            */

​

            :setvar DatabaseName "MessageQueue"

            :setvar DefaultFilePrefix "MessageQueue"

​

            GO

            :on error exit

            GO

            /*

            Detect SQLCMD mode and disable script execution if SQLCMD mode is not supported.

            To re-enable the script after enabling SQLCMD mode, execute the following:

            SET NOEXEC OFF;

            */

            :setvar __IsSqlCmdEnabled "True"

            GO

            IF N'$(__IsSqlCmdEnabled)' NOT LIKE N'True'

                BEGIN

                    PRINT N'SQLCMD mode must be enabled to successfully execute this script.';

                    SET NOEXEC ON;

                END

​

​

            GO

            USE [$(DatabaseName)];

​

            GO

            PRINT N'Creating SqlSchema [MessageQueue]...';

            """;

​

        // Set your variables here

        var variables = new Dictionary<string, string>();

​

        var batches = SqlCmdScriptParser.Parse(inputScript, variables);

​

        var i = 0;

        foreach (var batch in batches)

        {

            $"------------------ Batch {i++} ---------------".Dump();

            Console.WriteLine(batch);

        }

    }

}

​