feat: meter AI usage

JobTrackerApi/Controllers/AiUsageController.cs

@@ -0,0 +1,48 @@
+using JobTrackerApi.Data;
+using JobTrackerApi.Models;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+
+namespace JobTrackerApi.Controllers;
+
+[ApiController]
+[Route("api/ai/usage")]
+[Authorize(AuthenticationSchemes = "local")]
+public sealed class AiUsageController : ControllerBase
+{
+    private readonly UserManager<ApplicationUser> _users;
+    private readonly JobTrackerContext _db;
+
+    public AiUsageController(UserManager<ApplicationUser> users, JobTrackerContext db)
+    {
+        _users = users;
+        _db = db;
+    }
+
+    public sealed record UsagePeriodDto(int Calls, long InputCharacters, long OutputCharacters, long EstimatedTokens);
+    public sealed record UsageDto(UsagePeriodDto CurrentMonth, UsagePeriodDto AllTime);
+
+    [HttpGet]
+    public async Task<ActionResult<UsageDto>> Get(CancellationToken cancellationToken)
+    {
+        var user = await _users.GetUserAsync(User);
+        if (user is null) return Unauthorized();
+
+        var monthStart = new DateTimeOffset(DateTime.UtcNow.Year, DateTime.UtcNow.Month, 1, 0, 0, 0, TimeSpan.Zero);
+        return Ok(new UsageDto(
+            await SumAsync(_db.AiInteractions.Where(x => x.OwnerUserId == user.Id && x.CreatedAtUtc >= monthStart), cancellationToken),
+            await SumAsync(_db.AiInteractions.Where(x => x.OwnerUserId == user.Id), cancellationToken)));
+    }
+
+    private static async Task<UsagePeriodDto> SumAsync(IQueryable<AiInteraction> query, CancellationToken cancellationToken)
+    {
+        var totals = await query.GroupBy(_ => 1).Select(group => new UsagePeriodDto(
+            group.Count(),
+            group.Sum(x => (long)x.InputCharacterCount),
+            group.Sum(x => (long)x.OutputCharacterCount),
+            group.Sum(x => (long)x.EstimatedTokenCount))).FirstOrDefaultAsync(cancellationToken);
+        return totals ?? new UsagePeriodDto(0, 0, 0, 0);
+    }
+}

JobTrackerApi/Controllers/AiWorkspaceController.cs

@@ -26,7 +26,7 @@ public sealed class AiWorkspaceController : ControllerBase
     }
 
     public sealed record GenerateRequest(string Module, string? Mode, string? ExtraContext);
-    public sealed record InteractionDto(int Id, string Module, string? Mode, string Title, string Provider, JsonElement Result, DateTimeOffset CreatedAtUtc);
+    public sealed record InteractionDto(int Id, string Module, string? Mode, string Title, string Provider, JsonElement Result, int InputCharacterCount, int OutputCharacterCount, int EstimatedTokenCount, DateTimeOffset CreatedAtUtc);
 
     [HttpGet("modules")]
     public ActionResult<object> Modules() => Ok(new { modules = _workspace.Modules, provider = ResolveProvider() });
@@ -86,5 +86,5 @@ public sealed class AiWorkspaceController : ControllerBase
     private static InteractionDto ToDto(AiInteraction x) => new(
         x.Id, x.Module, x.Mode, x.Title, x.Provider,
         JsonSerializer.Deserialize<JsonElement>(string.IsNullOrWhiteSpace(x.ResultJson) ? "{}" : x.ResultJson),
-        x.CreatedAtUtc);
+        x.InputCharacterCount, x.OutputCharacterCount, x.EstimatedTokenCount, x.CreatedAtUtc);
 }