using System.Text.Json.Nodes;
using w4c_workflows.Models.Credentials;

namespace w4c_workflows.Services.Credentials;

/// <summary>Tokens pulled out of an OAuth-style token response.</summary>
public sealed record TokenSet(
    string AccessToken,
    string TokenType,
    int? ExpiresInSeconds,
    string? RefreshToken,
    string? Scope);

/// <summary>
/// Reads a token response using a type's extraction strategy. This is the
/// counterpart to <see cref="CredentialInjector"/>: injection places a token on a
/// request, extraction finds it in a token endpoint's response (dot-paths such as
/// <c>authed_user.access_token</c>). The OAuth refresh flow that consumes this is
/// a later increment; the strategy is modelled and tested now.
/// </summary>
public static class CredentialExtractor
{
    public static TokenSet? Extract(JsonObject tokenResponse, CredentialExtraction extraction)
    {
        var accessToken = ReadPath(tokenResponse, extraction.AccessTokenField);
        if (string.IsNullOrEmpty(accessToken))
            return null;

        var expiresIn = int.TryParse(ReadPath(tokenResponse, extraction.ExpiresInField), out var seconds)
            ? seconds
            : (int?)null;

        return new TokenSet(
            accessToken,
            ReadPath(tokenResponse, extraction.TokenTypeField) ?? extraction.DefaultTokenType,
            expiresIn,
            ReadPath(tokenResponse, extraction.RefreshTokenField),
            ReadPath(tokenResponse, extraction.ScopeField));
    }

    private static string? ReadPath(JsonObject root, string? path)
    {
        if (string.IsNullOrWhiteSpace(path))
            return null;

        JsonNode? current = root;
        foreach (var segment in path.Split('.', StringSplitOptions.RemoveEmptyEntries))
        {
            if (current is not JsonObject obj || !obj.TryGetPropertyValue(segment, out current))
                return null;
        }

        return current is JsonValue value && value.TryGetValue<string>(out var text)
            ? text
            : current?.ToJsonString();
    }
}