using Microsoft.EntityFrameworkCore;

namespace MeetingAssistant.Speakers;

internal static class SpeakerIdentitySchema
{
    public static async Task EnsureCreatedOrUpdatedAsync(
        SpeakerIdentityDbContext context,
        CancellationToken cancellationToken)
    {
        await context.Database.EnsureCreatedAsync(cancellationToken);
        await EnsureSpeakerIdentityTimestampColumnsAsync(context, cancellationToken);
        await context.Database.ExecuteSqlRawAsync(
            """
            CREATE TABLE IF NOT EXISTS "SpeakerAliases" (
                "Id" INTEGER NOT NULL CONSTRAINT "PK_SpeakerAliases" PRIMARY KEY AUTOINCREMENT,
                "SpeakerIdentityId" INTEGER NOT NULL,
                "Name" TEXT NOT NULL,
                CONSTRAINT "FK_SpeakerAliases_SpeakerIdentities_SpeakerIdentityId"
                    FOREIGN KEY ("SpeakerIdentityId") REFERENCES "SpeakerIdentities" ("Id") ON DELETE CASCADE
            );
            """,
            cancellationToken);
        await context.Database.ExecuteSqlRawAsync(
            """
            CREATE UNIQUE INDEX IF NOT EXISTS "IX_SpeakerAliases_SpeakerIdentityId_Name"
            ON "SpeakerAliases" ("SpeakerIdentityId", "Name");
            """,
            cancellationToken);
    }

    private static async Task EnsureSpeakerIdentityTimestampColumnsAsync(
        SpeakerIdentityDbContext context,
        CancellationToken cancellationToken)
    {
        const string defaultTimestamp = "1970-01-01T00:00:00.0000000+00:00";
        var hasCreatedAt = await HasColumnAsync(context, "SpeakerIdentities", "CreatedAt", cancellationToken);
        if (!hasCreatedAt)
        {
            await context.Database.ExecuteSqlRawAsync(
                $"""
                ALTER TABLE "SpeakerIdentities"
                ADD COLUMN "CreatedAt" TEXT NOT NULL DEFAULT '{defaultTimestamp}';
                """,
                cancellationToken);
        }

        var hasUpdatedAt = await HasColumnAsync(context, "SpeakerIdentities", "UpdatedAt", cancellationToken);
        if (!hasUpdatedAt)
        {
            await context.Database.ExecuteSqlRawAsync(
                $"""
                ALTER TABLE "SpeakerIdentities"
                ADD COLUMN "UpdatedAt" TEXT NOT NULL DEFAULT '{defaultTimestamp}';
                """,
                cancellationToken);
            await context.Database.ExecuteSqlRawAsync(
                $"""
                UPDATE "SpeakerIdentities"
                SET "UpdatedAt" = "CreatedAt"
                WHERE "UpdatedAt" = '{defaultTimestamp}';
                """,
                cancellationToken);
        }
    }

    private static async Task<bool> HasColumnAsync(
        SpeakerIdentityDbContext context,
        string tableName,
        string columnName,
        CancellationToken cancellationToken)
    {
        var connection = context.Database.GetDbConnection();
        var shouldClose = connection.State == System.Data.ConnectionState.Closed;
        if (shouldClose)
        {
            await connection.OpenAsync(cancellationToken);
        }

        try
        {
            await using var command = connection.CreateCommand();
            command.CommandText = $"""PRAGMA table_info("{tableName}")""";
            await using var reader = await command.ExecuteReaderAsync(cancellationToken);
            while (await reader.ReadAsync(cancellationToken))
            {
                if (string.Equals(reader.GetString(1), columnName, StringComparison.OrdinalIgnoreCase))
                {
                    return true;
                }
            }

            return false;
        }
        finally
        {
            if (shouldClose)
            {
                await connection.CloseAsync();
            }
        }
    }
}