Add Serilog console logging across the API

Information at endpoint and service-method boundaries, Debug in deeper
helpers, Warning before expected/recoverable failures (not-found,
validation, agent tool errors), Error on caught exceptions. Serilog
wraps the exception handler so request-completion logs report the
resolved status code rather than the raw exception. Never logs prose
bodies or the Anthropic API key.

src/Novelly.Api/Characters/CharacterArcService.cs

@@ -13,10 +13,12 @@ namespace Novelly.Api.Characters;
 /// on a supporting character. Demoting someone should not delete work, and a character
 /// who turns out to matter gets promoted after the arc is already sketched.
 /// </remarks>
-public class CharacterArcService(INovelDbContext db)
+public class CharacterArcService(INovelDbContext db, ILogger<CharacterArcService> logger)
 {
     public async Task<IReadOnlyList<ArcStageDto>> ListAsync(Guid characterId, CancellationToken ct = default)
     {
+        logger.LogInformation("Listing arc stages for character {CharacterId}", characterId);
+
         var stages = await Query()
             .Where(s => s.CharacterId == characterId)
             .OrderBy(s => s.SortOrder)
@@ -25,14 +27,23 @@ public class CharacterArcService(INovelDbContext db)
         return [.. stages.Select(s => s.ToDto())];
     }
 
-    public async Task<ArcStageDto> GetAsync(Guid id, CancellationToken ct = default) =>
-        (await FindAsync(id, ct)).ToDto();
+    public async Task<ArcStageDto> GetAsync(Guid id, CancellationToken ct = default)
+    {
+        logger.LogInformation("Getting arc stage {ArcStageId}", id);
+        return (await FindAsync(id, ct)).ToDto();
+    }
 
     public async Task<ArcStageDto> CreateAsync(
         Guid characterId, CreateArcStageRequest request, CancellationToken ct = default)
     {
-        var character = await db.Characters.FirstOrDefaultAsync(c => c.Id == characterId, ct)
-            ?? throw new NotFoundException(nameof(Character), characterId);
+        logger.LogInformation("Creating arc stage {Title} for character {CharacterId}", request.Title, characterId);
+
+        var character = await db.Characters.FirstOrDefaultAsync(c => c.Id == characterId, ct);
+        if (character is null)
+        {
+            logger.LogWarning("Character {CharacterId} not found", characterId);
+            throw new NotFoundException(nameof(Character), characterId);
+        }
 
         await EnsureChapterIsInSameProjectAsync(character, request.ChapterId, ct);
 
@@ -53,10 +64,16 @@ public class CharacterArcService(INovelDbContext db)
     public async Task<ArcStageDto> UpdateAsync(
         Guid id, UpdateArcStageRequest request, CancellationToken ct = default)
     {
+        logger.LogInformation("Updating arc stage {ArcStageId}", id);
+
         var stage = await FindAsync(id, ct);
 
-        var character = await db.Characters.FirstOrDefaultAsync(c => c.Id == stage.CharacterId, ct)
-            ?? throw new NotFoundException(nameof(Character), stage.CharacterId);
+        var character = await db.Characters.FirstOrDefaultAsync(c => c.Id == stage.CharacterId, ct);
+        if (character is null)
+        {
+            logger.LogWarning("Character {CharacterId} not found", stage.CharacterId);
+            throw new NotFoundException(nameof(Character), stage.CharacterId);
+        }
 
         await EnsureChapterIsInSameProjectAsync(character, request.ChapterId, ct);
 
@@ -72,6 +89,8 @@ public class CharacterArcService(INovelDbContext db)
 
     public async Task DeleteAsync(Guid id, CancellationToken ct = default)
     {
+        logger.LogInformation("Deleting arc stage {ArcStageId}", id);
+
         var stage = await FindAsync(id, ct);
         db.CharacterArcStages.Remove(stage);
         await db.SaveChangesAsync(ct);
@@ -84,6 +103,8 @@ public class CharacterArcService(INovelDbContext db)
     public async Task<IReadOnlyList<ArcStageDto>> ReorderAsync(
         Guid characterId, ReorderArcStagesRequest request, CancellationToken ct = default)
     {
+        logger.LogInformation("Reordering {Count} arc stages for character {CharacterId}", request.StageIds.Count, characterId);
+
         var stages = await db.CharacterArcStages
             .Where(s => s.CharacterId == characterId)
             .ToListAsync(ct);
@@ -91,6 +112,7 @@ public class CharacterArcService(INovelDbContext db)
         var missing = request.StageIds.Where(id => stages.All(s => s.Id != id)).ToList();
         if (missing.Count > 0)
         {
+            logger.LogWarning("Reorder for character {CharacterId} referenced missing arc stage {ArcStageId}", characterId, missing[0]);
             throw new NotFoundException(nameof(CharacterArcStage), missing[0]);
         }
 
@@ -117,10 +139,13 @@ public class CharacterArcService(INovelDbContext db)
             return;
         }
 
+        logger.LogDebug("Checking chapter {ChapterId} belongs to project {ProjectId}", id, character.ProjectId);
+
         var belongs = await db.Chapters.AnyAsync(c => c.Id == id && c.ProjectId == character.ProjectId, ct);
 
         if (!belongs)
         {
+            logger.LogWarning("Rejected arc stage: chapter {ChapterId} does not belong to project {ProjectId}", id, character.ProjectId);
             throw new InvalidOperationException(
                 "An arc stage can only point at a chapter in the same project as its character.");
         }
@@ -128,6 +153,8 @@ public class CharacterArcService(INovelDbContext db)
 
     private async Task<int> NextSortOrderAsync(Guid characterId, CancellationToken ct)
     {
+        logger.LogDebug("Computing next sort order for character {CharacterId}", characterId);
+
         var max = await db.CharacterArcStages
             .Where(s => s.CharacterId == characterId)
             .MaxAsync(s => (int?)s.SortOrder, ct);
@@ -137,7 +164,18 @@ public class CharacterArcService(INovelDbContext db)
 
     private IQueryable<CharacterArcStage> Query() => db.CharacterArcStages.Include(s => s.Chapter);
 
-    private async Task<CharacterArcStage> FindAsync(Guid id, CancellationToken ct) =>
-        await Query().FirstOrDefaultAsync(s => s.Id == id, ct)
-        ?? throw new NotFoundException(nameof(CharacterArcStage), id);
+    private async Task<CharacterArcStage> FindAsync(Guid id, CancellationToken ct)
+    {
+        logger.LogDebug("Finding arc stage {ArcStageId}", id);
+
+        var stage = await Query().FirstOrDefaultAsync(s => s.Id == id, ct);
+        if (stage is null)
+        {
+            logger.LogWarning("CharacterArcStage {ArcStageId} not found", id);
+            throw new NotFoundException(nameof(CharacterArcStage), id);
+        }
+
+        logger.LogDebug("Found arc stage {ArcStageId}", id);
+        return stage;
+    }
 }