using System;
using System.Reflection;

namespace Chernobyl.Reflection.Template.Xml
{
    /// <summary>
    /// Holds the namespace and the assembly in one type.
    /// </summary>
    public struct NamespaceAssembly
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="NamespaceAssembly"/> struct.
        /// </summary>
        /// <param name="namespace">The string that identifies the namespace 
        /// represented by this <see cref="NamespaceAssembly"/>.</param>
        /// <param name="assembly">The <see cref="AssemblyName"/> that this
        /// <see cref="NamespaceAssembly"/> represents.</param>
        public NamespaceAssembly(string @namespace, AssemblyName assembly)
            : this()
        {
            Namespace = @namespace;
            Assembly = assembly;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="NamespaceAssembly"/> struct.
        /// </summary>
        /// <param name="namespaceAssembly">The string that contains the 
        /// namespace and assembly. It should be formatted like so:
        /// clr-namespace:The.Namespace.Here; assembly=TheAssemblyNameHere</param>
        /// <exception cref="ArgumentException">Thrown if the 
        /// <paramref name="namespaceAssembly"/> does not contain the namespace
        /// qualifier "clr-namespace:", a semicolon that separates the namespace 
        /// and assembly strings, or the assembly qualifier "assembly=".</exception>
        public NamespaceAssembly(string namespaceAssembly) : this()
        {
            // Grab the namespace from the namespaceAssembly string.

            // Grab the location of the namespace qualifier.
            const string namespaceQualifier = "clr-namespace:";
            int indexOfNamespaceQualifier = namespaceAssembly.IndexOf(namespaceQualifier);
            if(indexOfNamespaceQualifier == -1)
                throw new ArgumentException("The namespace assembly string is badly formed. " +
                    "The string must include the namespace qualifier \"" + namespaceQualifier + 
                    "\" which specifies the namespace; this qualifier was not found. The value " +
                    "of the parameter was: \"" + namespaceAssembly + "\".", "namespaceAssembly");

            // Grab the location of the semicolon separating the namespace and
            // assembly.
            int lastIndexOfNamespace = indexOfNamespaceQualifier + namespaceQualifier.Length;
            int indexOfSemicolon = namespaceAssembly.IndexOf(';', lastIndexOfNamespace);
            if(indexOfSemicolon == -1)
                throw new ArgumentException("The namespace assembly string is badly formed. " + 
                    "The string must include a semicolon separating the namespace and assembly; " +
                    "no semicolon was found. The value of the parameter was: \"" + 
                    namespaceAssembly + "\".", "namespaceAssembly");

            Namespace = namespaceAssembly.Substring(lastIndexOfNamespace, indexOfSemicolon - namespaceQualifier.Length);

            // Grab the assembly name from the namespaceAssembly string.
            const string assemblyQualifier = "assembly=";
            int firstIndexOfAssembly = namespaceAssembly.IndexOf(assemblyQualifier, indexOfSemicolon);
            if (indexOfNamespaceQualifier == -1)
                throw new ArgumentException("The namespace assembly string is badly formed. " +
                    "The string must include the assembly qualifier \"" + assemblyQualifier +
                    "\" which specifies the assembly; this qualifier was not found. The value " +
                    "of the parameter was: \"" + namespaceAssembly + "\".", "namespaceAssembly");

            int lastIndexOfAssembly = firstIndexOfAssembly + assemblyQualifier.Length;
            string assemblyNameString = namespaceAssembly.Substring(lastIndexOfAssembly,
                                                                    namespaceAssembly.Length - lastIndexOfAssembly);
            Assembly = new AssemblyName(assemblyNameString);
        }

        /// <summary>
        /// The namespace.
        /// </summary>
        public string Namespace { get; private set; }

        /// <summary>
        /// The name of the assembly.
        /// </summary>
        public AssemblyName Assembly { get; private set; }
    }
}