//-----------------------------------------------------------------------
// <copyright file="Program.cs" company="lanedirt">
// Copyright (c) lanedirt. All rights reserved.
// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
// </copyright>
//-----------------------------------------------------------------------

using AliasServerDb;
using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata;

// Add return type for top-level statements
return await Run(args);

/// <summary>
/// Handles the migration of data between SQLite and PostgreSQL databases and password hashing utilities.
/// </summary>
public static partial class Program
{
    /// <summary>
    /// Runs the program with the given arguments.
    /// </summary>
    /// <param name="args">The command-line arguments.</param>
    /// <returns>The exit code of the program.</returns>
    public static async Task<int> Run(string[] args)
    {
        if (args.Length == 0)
        {
            Console.WriteLine("Usage:");
            Console.WriteLine("  hash-password <password>");
            Console.WriteLine("  migrate-sqlite <path-to-sqlite-db>");
            return 1;
        }

        switch (args[0].ToLower())
        {
            case "hash-password":
                if (args.Length != 2)
                {
                    Console.WriteLine("Usage: hash-password <password>");
                    return 1;
                }

                return HashPassword(args[1]);

            case "migrate-sqlite":
                if (args.Length != 3)
                {
                    Console.WriteLine("Usage: migrate-sqlite <path-to-sqlite-db> <postgresql-connection-string>");
                    return 1;
                }

                return await MigrateSqliteToPostgres(args[1], args[2]);

            default:
                Console.WriteLine("Unknown command. Available commands:");
                Console.WriteLine("  hash-password <password>");
                Console.WriteLine("  migrate-sqlite <path-to-sqlite-db> <postgresql-connection-string>");
                return 1;
        }
    }

    /// <summary>
    /// Hashes a password using ASP.NET Core Identity's password hasher.
    /// </summary>
    /// <param name="password">The plain text password to hash.</param>
    /// <returns>
    /// Returns 0 if the password was successfully hashed and printed to console.
    /// </returns>
    private static int HashPassword(string password)
    {
        var hasher = new PasswordHasher<IdentityUser>();
        var user = new AdminUser();
        var hashedPassword = hasher.HashPassword(user, password);
        Console.WriteLine(hashedPassword);
        return 0;
    }

    /// <summary>
    /// Migrates data from a SQLite database to a PostgreSQL database.
    /// </summary>
    /// <param name="sqliteDbPath">The file path to the source SQLite database.</param>
    /// <param name="pgConnString">The connection string to the PostgreSQL database.</param>
    /// <returns>
    /// Returns 0 if migration was successful, 1 if an error occurred.
    /// </returns>
    /// <exception cref="Exception">Thrown when a migration error occurs.</exception>
    private static async Task<int> MigrateSqliteToPostgres(string sqliteDbPath, string pgConnString)
    {
        try
        {
            if (!File.Exists(sqliteDbPath))
            {
                Console.WriteLine($"Error: SQLite database not found at {sqliteDbPath}");
                return 1;
            }

            Console.WriteLine($"Migrating SQLite database to PostgreSQL - start");

            // Create connections to both databases
            var sqliteConnString = $"Data Source={sqliteDbPath}";

            // Create contexts
            var optionsBuilderSqlite = new DbContextOptionsBuilder<AliasServerDbContext>()
                .UseSqlite(sqliteConnString);

            var optionsBuilderPg = new DbContextOptionsBuilder<AliasServerDbContext>()
                .UseNpgsql(pgConnString);

            // Make sure sqlite is on latest version migration
            Console.WriteLine("Update sqlite database to latest version...");
            await using var sqliteContext = new AliasServerDbContextSqlite(optionsBuilderSqlite.Options);
            await sqliteContext.Database.MigrateAsync();
            Console.WriteLine("Updating finished.");

            // Make sure postgres is on latest version migration
            Console.WriteLine("Update postgres database to latest version...");
            await using var pgContext = new AliasServerDbContextPostgresql(optionsBuilderPg.Options);
            await pgContext.Database.MigrateAsync();
            Console.WriteLine("Updating finished.");

            Console.WriteLine("Truncating existing tables in reverse dependency order...");

            // Truncate tables in reverse order of dependencies
            await TruncateTable(pgContext.EmailAttachments, "EmailAttachments");
            await TruncateTable(pgContext.Emails, "Emails");
            await TruncateTable(pgContext.UserTokens, "UserTokens");
            await TruncateTable(pgContext.UserRoles, "UserRoles");
            await TruncateTable(pgContext.UserLogin, "UserLogins");
            await TruncateTable(pgContext.UserEmailClaims, "UserEmailClaims");
            await TruncateTable(pgContext.Vaults, "Vaults");
            await TruncateTable(pgContext.UserEncryptionKeys, "UserEncryptionKeys");
            await TruncateTable(pgContext.AliasVaultUserRefreshTokens, "AliasVaultUserRefreshTokens");
            await TruncateTable(pgContext.Logs, "Logs");
            await TruncateTable(pgContext.AuthLogs, "AuthLogs");
            await TruncateTable(pgContext.DataProtectionKeys, "DataProtectionKeys");
            await TruncateTable(pgContext.ServerSettings, "ServerSettings");
            await TruncateTable(pgContext.TaskRunnerJobs, "TaskRunnerJobs");
            await TruncateTable(pgContext.AliasVaultUsers, "AliasVaultUsers");
            await TruncateTable(pgContext.AliasVaultRoles, "AliasVaultRoles");
            await TruncateTable(pgContext.AdminUsers, "AdminUsers");

            Console.WriteLine("Starting content migration...");

            // First, migrate tables without foreign key dependencies
            await MigrateTable(sqliteContext.AliasVaultRoles, pgContext.AliasVaultRoles, pgContext, "AliasVaultRoles");
            await MigrateTable(sqliteContext.AliasVaultUsers, pgContext.AliasVaultUsers, pgContext, "AliasVaultUsers");
            await MigrateTable(sqliteContext.ServerSettings, pgContext.ServerSettings, pgContext, "ServerSettings");
            await MigrateTable(sqliteContext.TaskRunnerJobs, pgContext.TaskRunnerJobs, pgContext, "TaskRunnerJobs", true);
            await MigrateTable(sqliteContext.DataProtectionKeys, pgContext.DataProtectionKeys, pgContext, "DataProtectionKeys", true);
            await MigrateTable(sqliteContext.Logs, pgContext.Logs, pgContext, "Logs", true);
            await MigrateTable(sqliteContext.AuthLogs, pgContext.AuthLogs, pgContext, "AuthLogs", true);
            await MigrateTable(sqliteContext.AdminUsers, pgContext.AdminUsers, pgContext, "AdminUsers");

            // Then migrate tables with foreign key dependencies
            await MigrateTable(sqliteContext.AliasVaultUserRefreshTokens, pgContext.AliasVaultUserRefreshTokens, pgContext, "AliasVaultUserRefreshTokens");
            await MigrateTable(sqliteContext.UserEncryptionKeys, pgContext.UserEncryptionKeys, pgContext, "UserEncryptionKeys");
            await MigrateTable(sqliteContext.UserEmailClaims, pgContext.UserEmailClaims, pgContext, "UserEmailClaims");
            await MigrateTable(sqliteContext.Vaults, pgContext.Vaults, pgContext, "Vaults");

            // Identity framework related tables
            await MigrateTable(sqliteContext.UserRoles, pgContext.UserRoles, pgContext, "UserRoles");
            await MigrateTable(sqliteContext.UserLogin, pgContext.UserLogin, pgContext, "UserLogins");
            await MigrateTable(sqliteContext.UserTokens, pgContext.UserTokens, pgContext, "UserTokens");

            // Email related tables (last due to dependencies)
            await MigrateTable(sqliteContext.Emails, pgContext.Emails, pgContext, "Emails", true);
            await MigrateTable(sqliteContext.EmailAttachments, pgContext.EmailAttachments, pgContext, "EmailAttachments", true);

            Console.WriteLine("Migration completed successfully!");
            return 0;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error during migration: {ex.Message}");
            Console.WriteLine(ex.InnerException);
            return 1;
        }
    }

    /// <summary>
    /// Truncates a table in the PostgreSQL database.
    /// </summary>
    /// <typeparam name="T">The entity type of the table being truncated.</typeparam>
    /// <param name="table">The database table to truncate.</param>
    /// <param name="tableName">The name of the table being truncated (for logging purposes).</param>
    /// <returns>A task representing the asynchronous truncation operation.</returns>
    private static async Task TruncateTable<T>(DbSet<T> table, string tableName)
    where T : class
    {
        Console.WriteLine($"Truncating table {tableName}...");
        var count = await table.CountAsync();
        if (count > 0)
        {
            await table.ExecuteDeleteAsync();
            Console.WriteLine($"Removed {count} records from {tableName}");
        }
    }

    /// <summary>
    /// Migrates data from one database table to another, handling the transfer in batches.
    /// </summary>
    /// <typeparam name="T">The entity type of the table being migrated.</typeparam>
    /// <param name="source">The source database table.</param>
    /// <param name="destination">The destination database table.</param>
    /// <param name="destinationContext">The destination database context.</param>
    /// <param name="tableName">The name of the table being migrated (for logging purposes).</param>
    /// <param name="resetSequence">Whether to reset the sequence for the table after migration.</param>
    /// <returns>A task representing the asynchronous migration operation.</returns>
    /// <exception cref="ArgumentException">
    /// Thrown when the number of records in source and destination tables don't match after migration.
    /// </exception>
    /// <exception cref="DbUpdateConcurrencyException">
    /// Thrown when a concurrency conflict occurs during the migration.
    /// </exception>
    private static async Task MigrateTable<T>(
        DbSet<T> source,
        DbSet<T> destination,
        DbContext destinationContext,
        string tableName,
        bool resetSequence = false)
        where T : class
    {
        Console.WriteLine($"Migrating {tableName}...");

        var items = await source.ToListAsync();
        Console.WriteLine($"Found {items.Count} records to migrate");

        if (items.Count > 0)
        {
            // Get entity type from the model to check annotations
            var entityType = destinationContext.Model.FindEntityType(typeof(T));

            foreach (var item in items)
            {
                HandleMaxLengthConstraints(item, entityType!, tableName);
            }

            const int batchSize = 50;
            foreach (var batch in items.Chunk(batchSize))
            {
                try
                {
                    await destination.AddRangeAsync(batch);
                    await destinationContext.SaveChangesAsync();
                    Console.WriteLine($"Migrated {batch.Length} records from {tableName}");
                }
                catch (DbUpdateConcurrencyException ex)
                {
                    Console.WriteLine($"Concurrency conflict occurred during migration of {tableName}...");
                    await HandleConcurrencyConflict(ex, destinationContext);
                    Console.WriteLine($"Concurrency conflict resolved, {batch.Length} records inserted");
                }
            }

            // Handle sequence reset logic...
            if (resetSequence && destinationContext.Database.ProviderName == "Npgsql.EntityFrameworkCore.PostgreSQL")
            {
                await ResetSequence<T>(destinationContext, tableName);
            }
        }

        // Ensure that the amount of records in the source and destination tables match
        if (await source.CountAsync() > await destination.CountAsync())
        {
            throw new ArgumentException($"The amount of records in the source is greater than the destination. Check if the migration is working correctly.");
        }
    }

    /// <summary>
    /// Handles max length constraints for string properties in an entity.
    /// </summary>
    /// <typeparam name="T">The entity type containing the properties to be processed.</typeparam>
    /// <param name="item">The entity instance containing the properties to be processed.</param>
    /// <param name="entityType">The entity type to be processed.</param>
    /// <param name="tableName">The name of the table being processed (for logging purposes).</param>
    private static void HandleMaxLengthConstraints<T>(T item, IEntityType entityType, string tableName)
        where T : class
    {
        foreach (var property in entityType.GetProperties())
        {
            // Only process string properties
            if (property.ClrType == typeof(string))
            {
                var maxLength = property.GetMaxLength();
                if (maxLength.HasValue)
                {
                    var propertyInfo = typeof(T).GetProperty(property.Name);
                    var value = propertyInfo?.GetValue(item) as string;

                    if (value?.Length > maxLength.Value)
                    {
                        propertyInfo!.SetValue(item, value.Substring(0, maxLength.Value));
                        Console.WriteLine($"Truncated {property.Name} in {tableName} from {value.Length} to {maxLength.Value} characters");
                    }
                }
            }
        }
    }

    /// <summary>
    /// Resets the sequence for a table in the PostgreSQL database.
    /// </summary>
    /// <typeparam name="T">The entity type of the table being reset.</typeparam>
    /// <param name="destinationContext">The destination database context.</param>
    /// <param name="tableName">The name of the table being reset (for logging purposes).</param>
    /// <returns>A task representing the asynchronous operation.</returns>
    private static async Task ResetSequence<T>(DbContext destinationContext, string tableName)
        where T : class
    {
        var tablePgName = destinationContext.Model.FindEntityType(typeof(T))?.GetTableName();
        if (!string.IsNullOrEmpty(tablePgName))
        {
            var schema = destinationContext.Model.FindEntityType(typeof(T))?.GetSchema() ?? "public";
            var sql = $"""
                SELECT setval(pg_get_serial_sequence('{schema}."{tablePgName}"', 'Id'),
                (SELECT COALESCE(MAX("Id"::integer), 0) + 1 FROM {schema}."{tablePgName}"), false);
                """;
            await destinationContext.Database.ExecuteSqlRawAsync(sql);
            Console.WriteLine($"Reset sequence for {tableName}");
        }
    }

    /// <summary>
    /// Handles a concurrency conflict by updating the original values with the database values.
    /// </summary>
    /// <param name="ex">The DbUpdateConcurrencyException that occurred.</param>
    /// <param name="destinationContext">The destination database context.</param>
    /// <returns>A task representing the asynchronous operation.</returns>
    private static async Task HandleConcurrencyConflict(
        DbUpdateConcurrencyException ex,
        DbContext destinationContext)
    {
        foreach (var entry in ex.Entries)
        {
            var databaseValues = await entry.GetDatabaseValuesAsync();
            if (databaseValues == null)
            {
                entry.State = EntityState.Detached;
            }
            else
            {
                entry.OriginalValues.SetValues(databaseValues);
                await destinationContext.SaveChangesAsync();
            }
        }
    }
}