1 files changed, 231 insertions, 0 deletions
diff --git a/store/works/Crupest.SecretTool/Crupest.SecretTool/Template.cs b/store/works/Crupest.SecretTool/Crupest.SecretTool/Template.cs
new file mode 100644
index 0000000..1fe91b1
--- /dev/null
+++ b/store/works/Crupest.SecretTool/Crupest.SecretTool/Template.cs
@@ -0,0 +1,231 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+
+namespace Crupest.SecretTool;
+
+public class Template
+{
+    private enum ParseState
+    {
+        Text,
+        Dollar,
+        LeftBracket,
+        VariableName,
+        VariableNameFinish,
+    }
+
+    private interface ITemplateNode
+    {
+        string Render(Dictionary<string, string> values);
+    }
+
+    private class TextNode(string text) : ITemplateNode
+    {
+
+        public string Text { get; } = text;
+
+        public string Render(Dictionary<string, string> values)
+        {
+            return Text;
+        }
+    }
+
+    private class VariableNode(string variableName) : ITemplateNode
+    {
+        public string VariableName { get; } = variableName;
+
+        public string Render(Dictionary<string, string> values)
+        {
+            return values.GetValueOrDefault(VariableName) ?? "";
+        }
+    }
+
+    public Template(string templateString)
+    {
+        TemplateString = templateString;
+        Nodes = Parse(templateString);
+        VariableNames = Nodes.OfType<VariableNode>().Select(node => node.VariableName).ToList();
+    }
+
+    private static List<ITemplateNode> Parse(string templateString)
+    {
+        int lineNumber = 1;
+        int columnNumber = 0;
+        List<ITemplateNode> nodes = [];
+        ParseState state = ParseState.Text;
+        StringBuilder stringBuilder = new();
+
+        string GetPosition() => $"line {lineNumber} column{columnNumber}";
+
+        [DoesNotReturn]
+        void ReportInvalidState(string message)
+        {
+            throw new Exception($"Invalid state at {GetPosition()}: {message}");
+        }
+
+        [DoesNotReturn]
+        void ReportInvalidCharacter(char c)
+        {
+            throw new FormatException($"Unexpected '{c}' at {GetPosition()}.");
+        }
+
+        void FinishText()
+        {
+            if (state != ParseState.Text)
+            {
+                ReportInvalidState($"Can't call FinishText here.");
+            }
+
+            if (stringBuilder.Length > 0)
+            {
+                nodes.Add(new TextNode(stringBuilder.ToString()));
+                stringBuilder.Clear();
+            }
+        }
+
+        foreach (var c in templateString)
+        {
+            if (c == '\n')
+            {
+                lineNumber++;
+                columnNumber = 0;
+            }
+
+            columnNumber++;
+
+            switch (c)
+            {
+                case '$':
+                    if (state == ParseState.Text)
+                    {
+                        FinishText();
+                        state = ParseState.Dollar;
+                    }
+                    else if (state == ParseState.Dollar)
+                    {
+                        if (stringBuilder.Length > 0)
+                        {
+                            throw new Exception($"Invalid state at {GetPosition()}: when we meet the second '$', text builder should be empty.");
+                        }
+                        stringBuilder.Append(c);
+                        state = ParseState.Text;
+                    }
+                    else
+                    {
+                        throw new FormatException($"Unexpected '$' at {GetPosition()}.");
+                    }
+                    break;
+                case '{':
+                    if (state == ParseState.Text)
+                    {
+                        stringBuilder.Append(c);
+                    }
+                    else if (state == ParseState.Dollar)
+                    {
+                        state = ParseState.LeftBracket;
+                    }
+                    else
+                    {
+                        throw new Exception($"Unexpected '{{' at {GetPosition()}.");
+                    }
+                    break;
+                case '}':
+                    if (state == ParseState.Text)
+                    {
+                        stringBuilder.Append(c);
+                        state = ParseState.Text;
+                    }
+                    else if (state == ParseState.VariableName || state == ParseState.VariableNameFinish)
+                    {
+                        nodes.Add(new VariableNode(stringBuilder.ToString()));
+                        stringBuilder.Clear();
+                        state = ParseState.Text;
+                    }
+                    else
+                    {
+                        ReportInvalidCharacter(c);
+                    }
+                    break;
+                default:
+                    if (state == ParseState.Dollar)
+                    {
+                        ReportInvalidCharacter(c);
+                    }
+
+                    if (char.IsWhiteSpace(c))
+                    {
+                        if (state == ParseState.LeftBracket || state == ParseState.VariableNameFinish)
+                        {
+                            continue;
+                        }
+                        else if (state == ParseState.Text)
+                        {
+                            stringBuilder.Append(c);
+                        }
+                        else if (state == ParseState.VariableName)
+                        {
+                            state = ParseState.VariableNameFinish;
+                        }
+                        else
+                        {
+                            ReportInvalidCharacter(c);
+                        }
+                    }
+                    else
+                    {
+                        if (state == ParseState.Text)
+                        {
+                            stringBuilder.Append(c);
+                        }
+                        else if (state == ParseState.LeftBracket || state == ParseState.VariableName)
+                        {
+                            stringBuilder.Append(c);
+                            state = ParseState.VariableName;
+                        }
+                        else
+                        {
+                            ReportInvalidCharacter(c);
+                        }
+                    }
+                    break;
+            }
+        }
+
+        if (state == ParseState.Text)
+        {
+            FinishText();
+        }
+        else
+        {
+            throw new FormatException("Unexpected end of template string.");
+        }
+
+        return nodes;
+    }
+
+    public string TemplateString { get; }
+    private List<ITemplateNode> Nodes { get; set; }
+    public List<string> VariableNames { get; }
+
+    public string Generate(Dictionary<string, string> values, bool allowMissingVariable = false)
+    {
+        StringBuilder stringBuilder = new();
+        foreach (var node in Nodes)
+        {
+            if (node is TextNode textNode)
+            {
+                stringBuilder.Append(textNode.Text);
+            }
+            else if (node is VariableNode variableNode)
+            {
+                var hasValue = values.TryGetValue(variableNode.VariableName, out var value);
+                if (!hasValue && !allowMissingVariable)
+                {
+                    throw new Exception($"Variable '{variableNode.VariableName}' is not set.");
+                }
+                stringBuilder.Append(hasValue ? value : string.Empty);
+            }
+        }
+        return stringBuilder.ToString();
+    }
+}