using System;
using System.Collections.Generic;
using System.IO;
using System.Text.Json;

namespace StellaOps.Scanner.Surface.Secrets.Providers;

internal sealed class FileSurfaceSecretProvider : ISurfaceSecretProvider
{
    private readonly string _root;

    public FileSurfaceSecretProvider(string root)
    {
        if (string.IsNullOrWhiteSpace(root))
        {
            throw new ArgumentException("File secret provider root cannot be null or whitespace.", nameof(root));
        }

        _root = root;
    }

    public SurfaceSecretHandle Get(SurfaceSecretRequest request)
    {
        if (request is null)
        {
            throw new ArgumentNullException(nameof(request));
        }

        var path = ResolvePath(request);
        if (!File.Exists(path))
        {
            throw new SurfaceSecretNotFoundException(request);
        }

        var json = File.ReadAllText(path);
        var descriptor = JsonSerializer.Deserialize<FileSecretDescriptor>(json);
        if (descriptor is null)
        {
            throw new SurfaceSecretNotFoundException(request);
        }

        if (string.IsNullOrWhiteSpace(descriptor.Payload))
        {
            return SurfaceSecretHandle.Empty;
        }

        var bytes = Convert.FromBase64String(descriptor.Payload);
        return SurfaceSecretHandle.FromBytes(bytes, descriptor.Metadata);
    }

    public async ValueTask<SurfaceSecretHandle> GetAsync(
        SurfaceSecretRequest request,
        CancellationToken cancellationToken = default)
    {
        if (request is null)
        {
            throw new ArgumentNullException(nameof(request));
        }

        var path = ResolvePath(request);
        if (!File.Exists(path))
        {
            throw new SurfaceSecretNotFoundException(request);
        }

        await using var stream = File.OpenRead(path);
        var descriptor = await JsonSerializer.DeserializeAsync<FileSecretDescriptor>(stream, cancellationToken: cancellationToken).ConfigureAwait(false);
        if (descriptor is null)
        {
            throw new SurfaceSecretNotFoundException(request);
        }

        if (string.IsNullOrWhiteSpace(descriptor.Payload))
        {
            return SurfaceSecretHandle.Empty;
        }

        var bytes = Convert.FromBase64String(descriptor.Payload);
        return SurfaceSecretHandle.FromBytes(bytes, descriptor.Metadata);
    }

    private string ResolvePath(SurfaceSecretRequest request)
    {
        var name = request.Name ?? "default";
        return Path.Combine(_root, request.Tenant, request.Component, request.SecretType, name + ".json");
    }

    private sealed class FileSecretDescriptor
    {
        public string? Payload { get; init; }
        public Dictionary<string, string>? Metadata { get; init; }
    }
}