/tags/v1.1/fadd/Data/Migration/SqlXmlMigrator.cs

using System;

using System.Collections.Generic;

using System.Data;

using System.IO;

using System.Reflection;

using System.Xml;



namespace Fadd.Data.Migration

{

    /// <summary>

    /// As the name implies the migrator uses sql specified for a certain driver to update the database.

    /// The sql is loaded using manifest resource xml files named xxxxx.fdmig.xml (fadd data migration)

    /// </summary>

    /// <remarks>

    /// The fdmig file should look like the following

    /// <![CDATA[

    /// <?xml version="1.0" encoding="utf-8" ?>

    /// <migrations>

    ///     <migration name="My migration" version="0002">

    ///         <description>

    ///             An optional description of the migration.

    ///         </description>

    /// 

    ///         <sql driver="MySql 1.0">

    ///             alter table myTable rename column myColumn to myColumnValues;

    ///         </sql>

    /// 

    ///         <sql driver="SqlServer">

    ///             alter table myTable rename column myColumn to myColumnValues;

    ///         </sql>

    ///     </migration>

    /// 

    ///     <migration name="My next migration" version="0003" description="A short description">

    ///         <!-- default driver will be used if specified and db doesn't match any other driver -->

    ///         <sql driver="default">

    ///             INSERT INTO myTable (myId, myValue) VALUES (13, '23123');

    ///         </sql>

    ///     </migration>

    ///     

    /// </migrations>

    /// ]]>

    /// </remarks>

    public class SqlXmlMigrator<MigrationModelType> : IMigrator where MigrationModelType : IMigrationModel, new()

    {

        private readonly Assembly[] _assemblies;

        private readonly SortedList<int, SqlMigration> _migrations = new SortedList<int, SqlMigration>();

        private int _highestVersion;

        private int _lowestVersion = int.MaxValue;



        /// <summary>Initializes the <see cref="SqlXmlMigrator{MigrationModelType}"/></summary>

        /// <param name="assemblies">Assemblies to look for fdmig.xml files in</param>

        public SqlXmlMigrator(params Assembly[] assemblies)

        {

            Check.Require(assemblies, "assemblies");



            _assemblies = assemblies;

        }



        public void Migrate(DataLayer dataLayer)

        {

            FetchMigrations();

            //if(_migrations.Count == 0)

              //  return;



            // Test migration

            if (TestMigration(dataLayer))

                return;



            // If migration failed we'll try if the first migration will fix it

            if (!_migrations.ContainsKey(_lowestVersion))

                throw new MigrationException("Could not find migration table or suitable first migration");



            ApplyMigration(dataLayer, _migrations[_lowestVersion]);

            TestMigration(dataLayer);            

        }



        private bool TestMigration(DataLayer dataLayer)

        {

            string tableName = dataLayer.MappingProviders.GetMapping(typeof(MigrationModelType).Name).TableName.ToLower();



            try

            {

                MigrationModelType lastMigration = dataLayer.Find<MigrationModelType>(new Statement("VersionNumber > ?", 0).OrderBy("VersionNumber DESC"))[0];

                if (lastMigration.VersionNumber >= _highestVersion)

                    return true;



                for (int i = lastMigration.VersionNumber + 1; i <= _highestVersion; ++i)

                {

                    if(!_migrations.ContainsKey(i))

                        throw new MigrationException("Could not find migration version: " + i);



                    ApplyMigration(dataLayer, _migrations[i]);

                }



                return true;

            }

            catch (Exception e)

            {

                // If the errror contains something like 'tablename does not exist' we will try to create the table using migration

                string error = e.Message.ToLower();

                if (!error.Contains(tableName) || !error.Contains("not") || !error.Contains("exist"))

                    throw;

            }



            return false;

        }



        private static void ApplyMigration(DataLayer dataLayer, SqlMigration migration)

        {

            string driver = dataLayer.ConnectionHelper.GetType().Name;

            string sql;

            if(!migration.Sql.TryGetValue(driver, out sql))

                if(!migration.Sql.TryGetValue("default", out sql))

                    throw new MigrationException("Could not find sql for migration version '" + migration.Version + "' and driver: " + driver);



            try

            {

                using (Transaction transaction = (Transaction)dataLayer.CreateTransaction())

                {

                    transaction.Execute(sql, new List<object>());

                    MigrationModelType migrationUpdate = new MigrationModelType

                                                             {

                                                                 VersionNumber = migration.Version,

                                                                 UpdateTime = DateTime.Now

                                                             };

                    transaction.Save(migrationUpdate);

                    transaction.Commit();

                }

            }

            catch (Exception e)

            {

                throw new MigrationException("Failed to execute sql migration version " + migration.Version, e);

            }

        }



        /// <summary>Reads all manifest files ending with fdmig.xml and creates migrations from them</summary>

        private void FetchMigrations()

        {

            foreach (Assembly assembly in _assemblies)

                foreach (string manifestResourceName in assembly.GetManifestResourceNames())

                    if(manifestResourceName.EndsWith("fdmig.xml"))

                        ParseMigrationXml(assembly, manifestResourceName);

        }



        private void ParseMigrationXml(Assembly containingAssembly, string manifestResourceName)

        {

            using(Stream stream = containingAssembly.GetManifestResourceStream(manifestResourceName))

            {

                if(stream == null)

                    throw new MigrationException("Could not read manifest resource file from assembly '" + containingAssembly.FullName + "': " + manifestResourceName);



                using (XmlTextReader reader = new XmlTextReader(stream))

                {

                    reader.WhitespaceHandling = WhitespaceHandling.None;

                    if (reader.Name == "xml")

                        if(!reader.Read())

                            throw new MigrationException("Invalid xml in migration file, missing node after 'xml' header node: " + manifestResourceName);



                    do

                    {

                        if(reader.Name == "migration")

                            ParseMigration(reader);



                    } while (reader.Read());

                }

            }

        }



        /// <summary>Parses the current 'migration' element in the reader and adds its value to the collection of migrations</summary>

        /// <param name="reader">The reader to parse the migration from</param>

        /// <exception cref="ArgumentNullException">If <paramref name="reader"/> is null</exception>

        /// <exception cref="MigrationXmlException">Throw if parsing failes due to invalid data in xml</exception>

        public void ParseMigration(XmlTextReader reader)

        {

            if(reader == null)

                throw new ArgumentNullException("reader");



            if(reader.Name != "migration")

                throw new MigrationXmlException("Element on line " + reader.LineNumber + " is not of type 'migration'.");



            if (reader.NodeType != XmlNodeType.Element)

                throw new MigrationXmlException("Migration element on line " + reader.LineNumber + " is end element.");



            string versionString = reader.GetAttribute("version");



            int version;

            if(!int.TryParse(versionString, out version))

                throw new MigrationXmlException("Migration element on line " + reader.LineNumber + " lacks a proper 'version' attribute.");



            if (_migrations.ContainsKey(version))

                throw new MigrationXmlException("Migration element on line " + reader.LineNumber + " specifies a version number that has already been added.");



            SqlMigration migration = new SqlMigration

                                         {

                                             Name = reader.GetAttribute("name"),

                                             Version = version,

                                             Description = reader.GetAttribute("description")

                                         };



            if (_highestVersion < version)

                _highestVersion = version;

            if (version < _lowestVersion)

                _lowestVersion = version;



            reader.Read();

            while(true)

            {

                if(reader.NodeType != XmlNodeType.Element)

                    continue;



                if (reader.Name == "sql")

                {

                    string driver = reader.GetAttribute("driver");

                    if (string.IsNullOrEmpty(driver))

                        throw new MigrationXmlException("Sql element on line " + reader.LineNumber + " lack a 'driver' attribute.");



                    if (migration.Sql.ContainsKey(driver))

                        throw new MigrationXmlException("Sql element on line " + reader.LineNumber + " specifies a driver that has already been added.");



                    string sql = reader.ReadElementContentAsString();

                    if (string.IsNullOrEmpty(sql))

                        throw new MigrationException("Sql element on line " + reader.LineNumber + " lacks proper sql content.");



                    migration.Sql.Add(driver, sql.Trim());

                }

                else if (reader.Name == "description")

                    migration.Description = reader.ReadElementContentAsString();

                else if (reader.Name != "migration")

                    if(!reader.Read())

                        break;



                if (reader.Name == "migration" && reader.NodeType == XmlNodeType.EndElement)

                    break;

            }



            _migrations.Add(migration.Version, migration);

        }

    }

}