using System.Text.Json;

namespace ClawdDotNet.Core.Deploymentcenter;

/// <summary>A sub-token issued for this instance.</summary>
/// <param name="Token">The plain text — delivered only once.</param>
/// <param name="TokenId">ID for revoking it in the administration.</param>
/// <param name="Scopes">Which rights were actually passed through.</param>
public sealed record ProvisionedToken(string Token, string TokenId, IReadOnlyList<string> Scopes);

/// <summary>
/// What a token says about itself (<c>GET /api/tokens/v1/whoami</c>, since SDK 2.7.1).
///
/// <para><see cref="ProjectSlug"/> is the field that matters. Since SDK 2.8.1
/// a watchdog monitor inherits the project of its ping token — if nothing is entered there,
/// the findings land in the phantom project "default", and a query for the own
/// project returns <b>zero findings</b> for a running, reporting instance. Supervision
/// would then look like "nothing unusual", and that is the worst of all
/// mistakes.</para>
/// </summary>
public sealed record TokenIdentity(
    string TokenId,
    string Name,
    string Type,
    string? ProjectSlug,
    string Environment,
    IReadOnlyList<string> Scopes)
{
    /// <summary>Whether this token is bound to a project — see the class comment.</summary>
    public bool IsProjectBound => !string.IsNullOrWhiteSpace(ProjectSlug);
}

/// <summary>
/// Access to <c>/api/tokens/v1/…</c>: issue a sub-token per instance
/// (<c>provision</c>) and ask a token about itself (<c>whoami</c>).
///
/// <para>This replaces the former self-registration via <c>POST /api/register</c> —
/// that endpoint does not exist in the Deploymentcenter (and in the old WatchDog server it
/// was the only way to get a token at all). The purpose stays the same
/// and is worth keeping: afterwards the instances do not hold the
/// master token, but a restricted one that can be revoked individually.</para>
///
/// <para>Rights can only be restricted in the process, never extended — what the
/// master token does not have, the sub-token does not get either.</para>
/// </summary>
public sealed class TokenProvisioner(DeploymentcenterApi api)
{
    /// <summary>What an instance needs: send heartbeats and report errors.</summary>
    public static readonly string[] InstanceScopes = ["watchdog:ping", "bugtracker:report"];

    public async Task<ProvisionedToken> ProvisionAsync(
        string clientName,
        string instanceId,
        IReadOnlyList<string> scopes,
        string environment = "production",
        CancellationToken ct = default)
    {
        var payload = new
        {
            client_name = clientName,
            instance_id = instanceId,
            scopes,
            environment
        };

        var response = await api.PostAsync("/api/tokens/v1/provision", payload, ct)
            .ConfigureAwait(false);

        var token = response.TryGetProperty("sub_token", out var t) && t.ValueKind == JsonValueKind.String
            ? t.GetString()
            : null;

        if (string.IsNullOrWhiteSpace(token))
        {
            throw new DeploymentcenterException(
                "no_token",
                "Die Provisionierung lieferte kein Token.",
                System.Net.HttpStatusCode.OK);
        }

        var tokenId = response.TryGetProperty("token_id", out var i) && i.ValueKind == JsonValueKind.String
            ? i.GetString() ?? ""
            : "";

        var granted = new List<string>();
        if (response.TryGetProperty("scopes", out var s) && s.ValueKind == JsonValueKind.Array)
        {
            granted.AddRange(s.EnumerateArray()
                .Where(e => e.ValueKind == JsonValueKind.String)
                .Select(e => e.GetString()!));
        }

        return new ProvisionedToken(token, tokenId, granted);
    }

    /// <summary>
    /// Asks the token this connection works with about itself.
    ///
    /// <para>Not curiosity, but the only way to learn the project binding:
    /// it is not in the token and does not follow from what was sent along when
    /// issuing it — it is a property the server keeps.
    /// See <see cref="TokenIdentity"/> for why that is not unimportant.</para>
    /// </summary>
    public async Task<TokenIdentity> WhoAmIAsync(CancellationToken ct = default)
    {
        var response = await api.GetAsync("/api/tokens/v1/whoami", ct).ConfigureAwait(false);

        var scopes = new List<string>();
        if (response.TryGetProperty("scopes", out var s) && s.ValueKind == JsonValueKind.Array)
        {
            scopes.AddRange(s.EnumerateArray()
                .Where(e => e.ValueKind == JsonValueKind.String)
                .Select(e => e.GetString()!));
        }

        return new TokenIdentity(
            Text(response, "token_id") ?? "",
            Text(response, "name") ?? "",
            Text(response, "type") ?? "unknown",
            Text(response, "project_slug"),
            Text(response, "environment") ?? "",
            scopes);
    }

    /// <summary>A string from the response; <c>null</c> also for JSON <c>null</c>.</summary>
    private static string? Text(JsonElement root, string name)
        => root.TryGetProperty(name, out var v) && v.ValueKind == JsonValueKind.String
            ? v.GetString()
            : null;
}