feat: add validate and constraints

Adds a validate method and a basic set of constraints.

.gitignore

@@ -1,24 +1,3 @@
-# Compiled Object files
-*.o
-*.obj
-
-# Compiled Dynamic libraries
-*.so
-*.dylib
-*.dll
-
-# Compiled Static libraries
+dutils-validation-test-library
 *.a
-*.lib
-
-# Executables
-*.exe
-
-# DUB
 .dub
-docs.json
-__dummy.html
-docs/
-
-# Code coverage
-*.lst

.travis.yml

@@ -0,0 +1,5 @@
+language: d
+
+branches:
+  only:
+    - master

README.md

@@ -1,2 +1,34 @@
 # validation
+
+[![DUB Package](https://img.shields.io/dub/v/dutils-validation.svg)](https://code.dlang.org/packages/dutils-validation)
+[![Posix Build Status](https://travis-ci.org/d-utils/validation.svg?branch=master)](https://travis-ci.org/d-utils/validation)
+
 Validation annotations for dlang structs
+
+## example
+
+    import dutils.validation.constraints : ValidateRequired, ValidateEmail
+
+    struct Email {
+      @ValidateRequired()
+      @ValidateEmail()
+      string to;
+
+      @ValidateRequired()
+      @ValidateEmail()
+      string from;
+
+      @ValidateMinimumLength(3)
+      @ValidateMaximumLength(100)
+      string subject;
+
+      string body;
+    }
+
+    auto email = Email("badto.address", "name@example.com", "no", "some body");
+
+    validate(email); // throws an instance of ValidationErrors
+
+## TODO
+
+- [ ] Support for nested structs and arrays

dub.json

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+{
+	"name": "dutils-validation",
+	"description": "Validation annotations for dlang structs",
+	"homepage": "https://github.com/d-utils/validation",
+	"authors": [
+		"Fredrik Söderström"
+	],
+	"copyright": "Copyright © 2020, Fredrik Söderström",
+	"license": "MIT",
+	"targetType": "library"
+}

source/dutils/validation/constraints.d

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+module dutils.validation.constraints;
+
+import std.conv : to;
+import std.typecons : Nullable;
+
+import dutils.validation.validate : ValidationError;
+
+struct ValidateRequired {
+  Nullable!ValidationError getError(T)(T value, string path) {
+    if (value) {
+      return Nullable!ValidationError.init;
+    }
+
+    return Nullable!ValidationError(ValidationError(path,
+        ValidationErrorTypes.required, "Required to have a value"));
+  }
+}
+
+struct ValidateEmail {
+  Nullable!ValidationError getError(string value, string path) {
+    import dutils.validation.email : isValidEmail;
+
+    if (isValidEmail(value)) {
+      return Nullable!ValidationError.init;
+    }
+
+    return Nullable!ValidationError(ValidationError(path,
+        ValidationErrorTypes.email, "Value must be an email string"));
+  }
+}
+
+struct ValidateMinimum(T) {
+  T minimum;
+
+  Nullable!ValidationError getError(T value, string path) {
+    if (value.to!T >= this.minimum) {
+      return Nullable!ValidationError.init;
+    }
+
+    return Nullable!ValidationError(ValidationError(path, ValidationErrorTypes.minimum,
+        "Value cannot be less than " ~ this.minimum.to!string,
+        ["minimum": this.minimum.to!double]));
+  }
+}
+
+struct ValidateMaximum(T) {
+  T maximum;
+
+  Nullable!ValidationError getError(T value, string path) {
+    if (value.to!T <= this.maximum) {
+      return Nullable!ValidationError.init;
+    }
+
+    return Nullable!ValidationError(ValidationError(path, ValidationErrorTypes.maximum,
+        "Value cannot be greater isBuiltinTypethan " ~ this.maximum.to!string,
+        ["maximum": this.maximum.to!double]));
+  }
+}
+
+struct ValidateMinimumLength {
+  uint minimumLength;
+
+  Nullable!ValidationError getError(string value, string path) {
+    if (value.length >= this.minimumLength) {
+      return Nullable!ValidationError.init;
+    }
+
+    return Nullable!ValidationError(ValidationError(path, ValidationErrorTypes.minimumLength,
+        "Value cannot be shorter than " ~ this.minimumLength.to!string,
+        ["minimumLength": this.minimumLength.to!double]));
+  }
+}
+
+struct ValidateMaximumLength {
+  uint maximumLength;
+
+  Nullable!ValidationError getError(string value, string path) {
+    if (value.length <= this.maximumLength) {
+      return Nullable!ValidationError.init;
+    }
+
+    return Nullable!ValidationError(ValidationError(path, ValidationErrorTypes.maximumLength,
+        "Value cannot be longer than " ~ this.maximumLength.to!string,
+        ["maximumLength": this.maximumLength.to!double]));
+  }
+}
+
+enum ValidationErrorTypes {
+  type = "type",
+  required = "required",
+  email = "email",
+  minimum = "minimum",
+  maximum = "maximum",
+  minimumLength = "minimumLength",
+  maximumLength = "maximumLength"
+}

source/dutils/validation/email.d

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+module dutils.validation.email;
+
+import std.regex : ctRegex, replace;
+
+bool isValidEmail(string email) {
+  import std.typecons : No;
+  import std.net.isemail : isEmail, EmailStatusCode;
+
+  const result = isEmail(extractEmail(email), No.checkDns, EmailStatusCode.none);
+  return result.statusCode == EmailStatusCode.valid;
+}
+
+const extractEmailPattern = ctRegex!r"^(.*?<\s*)?([^@]+@[^>]+).*$";
+
+string extractEmail(string email) {
+  return replace(email, extractEmailPattern, "$2");
+}
+
+/**
+ * extractEmail - Don't modify string without email
+ */
+unittest {
+  assert(extractEmail("this is not an email<noat>") == "this is not an email<noat>");
+}
+
+/**
+ * extractEmail - Don't modify string with only email
+ */
+unittest {
+  assert(extractEmail("anna.andersson@example.com") == "anna.andersson@example.com");
+}
+
+/**
+ * extractEmail - Extract email from string
+ */
+unittest {
+  assert(extractEmail(
+      "\"Anna Andersson\" <anna.andersson@example.com>") == "anna.andersson@example.com");
+}
+
+/**
+ * isValidEmail - Valid email should return true
+ */
+unittest {
+  assert(isValidEmail("\"Anna Andersson\" <anna.andersson@example.com>"));
+}
+
+/**
+ * isValidEmail - Invalid email should return false
+ */
+unittest {
+  assert(!isValidEmail("\"Anna Andersson\" <anna.anderssonexample.com>"));
+  assert(!isValidEmail("Anna Andersson"));
+}