using System.Text.Json;
using Api.Responses;
using Api.Services.Contracts;
using Microsoft.Data.SqlClient;

namespace Api.Services;

public sealed class SqlMatcherRepository : IMatcherRepository
{
    private readonly string _connectionString;

    public SqlMatcherRepository(IConfiguration configuration)
    {
        _connectionString = configuration.GetConnectionString("CvMatcherDb")
            ?? throw new InvalidOperationException("Connection string 'CvMatcherDb' is missing.");
    }

    public async Task InitializeAsync(CancellationToken ct)
    {
        await EnsureDatabaseExistsAsync(ct);
        var sql = await File.ReadAllTextAsync(Path.Combine(AppContext.BaseDirectory, "Database", "schema.sql"), ct);
        await using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync(ct);
        foreach (var commandText in sql.Split("GO", StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries))
        {
            await using var command = new SqlCommand(commandText, connection);
            await command.ExecuteNonQueryAsync(ct);
        }
    }

    public async Task<JobMatchResponse?> GetMatchAsync(string cvDocumentId, string jobDocumentId, CancellationToken ct)
    {
        const string sql = "SELECT ResultJson FROM CvMatchResults WHERE CvDocumentId = @CvDocumentId AND JobDocumentId = @JobDocumentId";
        await using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync(ct);
        await using var command = new SqlCommand(sql, connection);
        command.Parameters.AddWithValue("@CvDocumentId", cvDocumentId);
        command.Parameters.AddWithValue("@JobDocumentId", jobDocumentId);
        var json = await command.ExecuteScalarAsync(ct) as string;
        if (string.IsNullOrWhiteSpace(json)) return null;
        var result = JsonSerializer.Deserialize<JobMatchResponse>(json, new JsonSerializerOptions(JsonSerializerDefaults.Web));
        if (result is not null) result.Cached = true;
        return result;
    }

    public async Task SaveMatchAsync(string cvDocumentId, string jobDocumentId, JobMatchResponse response, CancellationToken ct)
    {
        const string sql = """
            IF NOT EXISTS (SELECT 1 FROM CvMatchResults WHERE CvDocumentId = @CvDocumentId AND JobDocumentId = @JobDocumentId)
            INSERT INTO CvMatchResults (Id, CvDocumentId, JobDocumentId, ResultJson, Score, CreatedAt)
            VALUES (@Id, @CvDocumentId, @JobDocumentId, @ResultJson, @Score, SYSUTCDATETIME())
            """;
        await using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync(ct);
        await using var command = new SqlCommand(sql, connection);
        command.Parameters.AddWithValue("@Id", Guid.NewGuid().ToString("N"));
        command.Parameters.AddWithValue("@CvDocumentId", cvDocumentId);
        command.Parameters.AddWithValue("@JobDocumentId", jobDocumentId);
        command.Parameters.AddWithValue("@ResultJson", JsonSerializer.Serialize(response, new JsonSerializerOptions(JsonSerializerDefaults.Web)));
        command.Parameters.AddWithValue("@Score", response.Score);
        await command.ExecuteNonQueryAsync(ct);
    }

    public async Task<string?> GetChatCompletionAsync(string cacheKey, CancellationToken ct)
    {
        const string sql = "SELECT ResponseText FROM CvMatcherChatCache WHERE CacheKey = @CacheKey";
        await using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync(ct);
        await using var command = new SqlCommand(sql, connection);
        command.Parameters.AddWithValue("@CacheKey", cacheKey);
        return await command.ExecuteScalarAsync(ct) as string;
    }

    public async Task SaveChatCompletionAsync(string cacheKey, string model, decimal temperature, string responseText, CancellationToken ct)
    {
        const string sql = """
            IF NOT EXISTS (SELECT 1 FROM CvMatcherChatCache WHERE CacheKey = @CacheKey)
            INSERT INTO CvMatcherChatCache (CacheKey, Model, Temperature, ResponseText, CreatedAt)
            VALUES (@CacheKey, @Model, @Temperature, @ResponseText, SYSUTCDATETIME())
            """;
        await using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync(ct);
        await using var command = new SqlCommand(sql, connection);
        command.Parameters.AddWithValue("@CacheKey", cacheKey);
        command.Parameters.AddWithValue("@Model", model);
        command.Parameters.AddWithValue("@Temperature", temperature);
        command.Parameters.AddWithValue("@ResponseText", responseText);
        await command.ExecuteNonQueryAsync(ct);
    }
    private async Task EnsureDatabaseExistsAsync(CancellationToken ct)
    {
        var builder = new SqlConnectionStringBuilder(_connectionString);
        var databaseName = builder.InitialCatalog;
        if (string.IsNullOrWhiteSpace(databaseName)) return;

        builder.InitialCatalog = "master";
        await using var connection = new SqlConnection(builder.ConnectionString);
        await connection.OpenAsync(ct);
        var safeName = databaseName.Replace("]", "]]" );
        await using var command = new SqlCommand($"IF DB_ID(@DatabaseName) IS NULL EXEC('CREATE DATABASE [{safeName}]')", connection);
        command.Parameters.AddWithValue("@DatabaseName", databaseName);
        await command.ExecuteNonQueryAsync(ct);
    }

}