Init

Services/UsageService.cs

@@ -0,0 +1,113 @@
+using System.IO;
+using System.Net.Http;
+using System.Text.Json;
+using ClaudeOverview.Models;
+
+namespace ClaudeOverview.Services;
+
+/// <summary>
+/// Fetches subscription usage (session / weekly limits) from the same endpoint Claude
+/// Code's /usage command uses, authenticating with the OAuth token stored in
+/// ~/.claude/.credentials.json (read fresh each call so it tracks token refreshes).
+/// </summary>
+public sealed class UsageService
+{
+    private const string Endpoint = "https://api.anthropic.com/api/oauth/usage";
+
+    private static readonly HttpClient Http = new() { Timeout = TimeSpan.FromSeconds(12) };
+
+    private readonly AppConfig _config;
+
+    public UsageService(AppConfig config) => _config = config;
+
+    public async Task<UsageInfo> FetchAsync()
+    {
+        try
+        {
+            var token = ReadAccessToken(out var tokenError);
+            if (token is null) return new UsageInfo { Error = tokenError };
+
+            using var req = new HttpRequestMessage(HttpMethod.Get, Endpoint);
+            req.Headers.TryAddWithoutValidation("Authorization", "Bearer " + token);
+            req.Headers.TryAddWithoutValidation("anthropic-beta", "oauth-2025-04-20");
+
+            using var resp = await Http.SendAsync(req);
+            if (!resp.IsSuccessStatusCode)
+            {
+                if (resp.StatusCode == System.Net.HttpStatusCode.TooManyRequests)
+                {
+                    return new UsageInfo
+                    {
+                        Error = "rate limited (429 — backing off)",
+                        RateLimited = true,
+                        RetryAfter = resp.Headers.RetryAfter?.Delta
+                            ?? (resp.Headers.RetryAfter?.Date is { } retryAt
+                                ? retryAt.ToUniversalTime() - DateTimeOffset.UtcNow
+                                : null),
+                    };
+                }
+
+                var hint = resp.StatusCode == System.Net.HttpStatusCode.Unauthorized
+                    ? " (token expired — open Claude Code to refresh)"
+                    : "";
+                return new UsageInfo { Error = $"usage HTTP {(int)resp.StatusCode}{hint}" };
+            }
+
+            await using var stream = await resp.Content.ReadAsStreamAsync();
+            using var doc = await JsonDocument.ParseAsync(stream);
+            var root = doc.RootElement;
+
+            var info = new UsageInfo();
+            if (root.TryGetProperty("five_hour", out var fh) && fh.ValueKind == JsonValueKind.Object)
+            {
+                info.SessionPercent = GetDouble(fh, "utilization");
+                info.SessionResetsAt = GetDate(fh, "resets_at");
+            }
+            if (root.TryGetProperty("seven_day", out var sd) && sd.ValueKind == JsonValueKind.Object)
+            {
+                info.WeeklyPercent = GetDouble(sd, "utilization");
+                info.WeeklyResetsAt = GetDate(sd, "resets_at");
+            }
+            return info;
+        }
+        catch (Exception ex)
+        {
+            return new UsageInfo { Error = ex.Message };
+        }
+    }
+
+    private string? ReadAccessToken(out string? error)
+    {
+        error = null;
+        var path = _config.CredentialsPath;
+        if (!File.Exists(path)) { error = "not signed in (no credentials)"; return null; }
+
+        try
+        {
+            using var fs = File.OpenRead(path);
+            using var doc = JsonDocument.Parse(fs);
+            if (!doc.RootElement.TryGetProperty("claudeAiOauth", out var oauth))
+            {
+                error = "no OAuth session";
+                return null;
+            }
+            var token = oauth.TryGetProperty("accessToken", out var t) ? t.GetString() : null;
+            if (string.IsNullOrEmpty(token)) { error = "no access token"; return null; }
+            return token;
+        }
+        catch (Exception ex)
+        {
+            error = $"credentials read failed: {ex.Message}";
+            return null;
+        }
+    }
+
+    private static double GetDouble(JsonElement e, string name) =>
+        e.TryGetProperty(name, out var p) && p.ValueKind == JsonValueKind.Number ? p.GetDouble() : 0;
+
+    private static DateTime? GetDate(JsonElement e, string name) =>
+        e.TryGetProperty(name, out var p) && p.ValueKind == JsonValueKind.String &&
+        DateTime.TryParse(p.GetString(), null,
+            System.Globalization.DateTimeStyles.AdjustToUniversal, out var dt)
+            ? dt : null;
+}