Init implementation for the Open API validation

src/Microsoft.OpenApi/Properties/SRResource.resx

@@ -177,4 +177,10 @@
   <data name="SourceExpressionHasInvalidFormat" xml:space="preserve">
     <value>The source expression '{0}' has invalid format.</value>
   </data>
+  <data name="Validation_PathItemMustBeginWithSlash" xml:space="preserve">
+    <value>The path item name '{0}' MUST begin with a slash.</value>
+  </data>
+  <data name="Validation_StringMustBeEmailAddress" xml:space="preserve">
+    <value>The string '{0}' MUST be in the format of an email address.</value>
+  </data>
 </root>

src/Microsoft.OpenApi/Validations/OpenApiElementValidator.cs

@@ -0,0 +1,75 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.OpenApi.Interfaces;
+using Microsoft.OpenApi.Validations.Rules;
+
+namespace Microsoft.OpenApi.Validations
+{
+    /// <summary>
+    /// The public APIs to validate the Open API element.
+    /// </summary>
+    public static class OpenApiElementValidator
+    {
+        /// <summary>
+        /// Validate the Open API element.
+        /// </summary>
+        /// <typeparam name="T">The Open API element type.</typeparam>
+        /// <param name="element">The Open API element.</param>
+        /// <returns>True means no errors, otherwise with errors.</returns>
+        public static bool Validate<T>(this T element) where T : IOpenApiElement
+        {
+            IEnumerable<ValidationError> errors;
+            return element.Validate(out errors);
+        }
+
+        /// <summary>
+        /// Validate the Open API element.
+        /// </summary>
+        /// <typeparam name="T">The Open API element type.</typeparam>
+        /// <param name="element">The Open API element.</param>
+        /// <param name="errors">The output errors.</param>
+        /// <returns>True means no errors, otherwise with errors.</returns>
+        public static bool Validate<T>(this T element, out IEnumerable<ValidationError> errors)
+            where T : IOpenApiElement
+        {
+            ValidationRuleSet ruleSet = ValidationRuleSet.DefaultRuleSet;
+            return element.Validate(ruleSet, out errors);
+        }
+
+        /// <summary>
+        ///  Validate the Open API element.
+        /// </summary>
+        /// <typeparam name="T">The Open API element type.</typeparam>
+        /// <param name="element">The Open API element.</param>
+        /// <param name="ruleSet">The input rule set.</param>
+        /// <param name="errors">The output errors.</param>
+        /// <returns>True means no errors, otherwise with errors.</returns>
+        public static bool Validate<T>(this T element, ValidationRuleSet ruleSet, out IEnumerable<ValidationError> errors)
+            where T : IOpenApiElement
+        {
+            errors = null;
+            if (element == null)
+            {
+                return true;
+            }
+
+            if (ruleSet == null)
+            {
+                ruleSet = ValidationRuleSet.DefaultRuleSet;
+            }
+
+            ValidationContext context = new ValidationContext(ruleSet);
+
+            context.Validate(element);
+
+            errors = context.Errors;
+
+            return !errors.Any();
+        }
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/OpenApiComponentsRules.cs

@@ -0,0 +1,16 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using Microsoft.OpenApi.Models;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    /// <summary>
+    /// The validation rules for <see cref="OpenApiComponents"/>.
+    /// </summary>
+    public static class OpenApiComponentsRules
+    {
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/OpenApiContactRules.cs

@@ -0,0 +1,52 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using System;
+using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Properties;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    /// <summary>
+    /// The validation rules for <see cref="OpenApiContact"/>.
+    /// </summary>
+    internal static class OpenApiContactRules
+    {
+        /// <summary>
+        /// Email field MUST be email address.
+        /// </summary>
+        public static readonly ValidationRule<OpenApiContact> EmailMustBeEmailFormat =
+            new ValidationRule<OpenApiContact>(
+                (context, item) =>
+                {
+                    context.Push("email");
+                    if (item != null && item.Email != null)
+                    {
+                        if (!item.Email.IsEmailAddress())
+                        {
+                            ValidationError error = new ValidationError(ErrorReason.EmailFormat, context.PathString,
+                                String.Format(SRResource.Validation_StringMustBeEmailAddress, item.Email));
+                            context.AddError(error);
+                        }
+                    }
+                    context.Pop();
+                });
+
+        /// <summary>
+        /// Url field MUST be url format.
+        /// </summary>
+        public static readonly ValidationRule<OpenApiContact> UrlMustBeUrlFormat =
+            new ValidationRule<OpenApiContact>(
+                (context, item) =>
+                {
+                    context.Push("url");
+                    if (item != null && item.Url != null)
+                    {
+                        // TODO:
+                    }
+                    context.Pop();
+                });
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/OpenApiDocumentRules.cs

@@ -0,0 +1,41 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using Microsoft.OpenApi.Models;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    /// <summary>
+    /// The validation rules for <see cref="OpenApiDocument"/>.
+    /// </summary>
+    internal static class OpenApiDocumentRules
+    {
+        /// <summary>
+        /// The Info field is required.
+        /// </summary>
+        public static readonly ValidationRule<OpenApiDocument> InfoIsRequired =
+            new ValidationRule<OpenApiDocument>(
+                (context, item) =>
+                {
+                    if (item.Info == null)
+                    {
+                        //context.AddError();
+                    }
+                });
+
+        /// <summary>
+        /// The Paths field is required.
+        /// </summary>
+        public static readonly ValidationRule<OpenApiDocument> PathsIsRequired =
+            new ValidationRule<OpenApiDocument>(
+                (context, item) =>
+                {
+                    if (item.Paths == null)
+                    {
+                        //context.AddError();
+                    }
+                });
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/OpenApiExtensionRules.cs

@@ -0,0 +1,28 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using Microsoft.OpenApi.Interfaces;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    /// <summary>
+    /// The validation rules for <see cref="IOpenApiExtensible"/>.
+    /// </summary>
+    public static class OpenApiExtensibleRules
+    {
+        /// <summary>
+        /// Extension name MUST start with "x-".
+        /// </summary>
+        private static readonly ValidationRule<IOpenApiExtensible> ExtensionNameMustStartWithXDollar =
+            new ValidationRule<IOpenApiExtensible>(
+                (context, item) =>
+                {
+                    foreach (var extensible in item.Extensions)
+                    {
+
+                    }
+                });
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/OpenApiInfoRules.cs

@@ -0,0 +1,31 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using System;
+using Microsoft.OpenApi.Models;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    /// <summary>
+    /// The validation rules for <see cref="OpenApiInfo"/>.
+    /// </summary>
+    internal static class OpenApiInfoRules
+    {
+        /// <summary>
+        /// The title of the application is required.
+        /// </summary>
+        public static readonly ValidationRule<OpenApiInfo> TitleIsRequired =
+            new ValidationRule<OpenApiInfo>(
+                (context, item) =>
+                {
+                    if (String.IsNullOrEmpty(item.Title))
+                    {
+                        // add error.
+                    }
+                });
+
+        // add more rule.
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/OpenApiPathsRules.cs

@@ -0,0 +1,46 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Properties;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    /// <summary>
+    /// The validation rules for <see cref="OpenApiPaths"/>.
+    /// </summary>
+    public static class OpenApiPathsRules
+    {
+        /// <summary>
+        /// A relative path to an individual endpoint. The field name MUST begin with a slash. 
+        /// </summary>
+        public static readonly ValidationRule<OpenApiPaths> PathNameMustBeginWithSlash =
+            new ValidationRule<OpenApiPaths>(
+                (context, item) =>
+                {
+                    foreach (var pathName in item.Keys)
+                    {
+                        context.Push(pathName);
+
+                        if (string.IsNullOrEmpty(pathName))
+                        {
+                            // Add the error message
+                            // context.Add(...);
+                        }
+
+                        if (!pathName.StartsWith("/"))
+                        {
+                            ValidationError error = new ValidationError(ErrorReason.Format, context.PathString,
+                                string.Format(SRResource.Validation_PathItemMustBeginWithSlash, pathName));
+                            context.AddError(error);
+                        }
+
+                        context.Pop();
+                    }
+                });
+
+        // add more rules
+    }
+}

src/Microsoft.OpenApi/Validations/Rules/RuleHelpers.cs

@@ -0,0 +1,40 @@
+// ------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All rights reserved.
+//  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
+// ------------------------------------------------------------
+
+using System;
+
+namespace Microsoft.OpenApi.Validations.Rules
+{
+    internal static class RuleHelpers
+    {
+        /// <summary>
+        /// Input string must be in the format of an email address
+        /// </summary>
+        /// <param name="input">The input string.</param>
+        /// <returns></returns>
+        public static bool IsEmailAddress(this string input)
+        {
+            if (String.IsNullOrEmpty(input))
+            {
+                return false;
+            }
+
+            var splits = input.Split('@');
+            if (splits.Length != 2)
+            {
+                return false;
+            }
+
+            if (String.IsNullOrEmpty(splits[0]) || String.IsNullOrEmpty(splits[1]))
+            {
+                return false;
+            }
+
+            // Add more rules.
+
+            return true;
+        }
+    }
+}