refactor: extract magic byte detection into internal/magic package #42

clawbot · 2026-03-26T01:46:59+01:00

clawbot commented

2026-03-26 01:46:59 +01:00

Summary

Extract magic byte detection and MIME type handling from internal/imgcache/ into a new focused internal/magic/ package.

Part of issue #39

Changes

New package: `internal/magic/`

Moved the following from internal/imgcache/magic.go:

MIMEType type and constants (MIMETypeJPEG, MIMETypePNG, etc.)
DetectFormat() — detects image format from magic bytes
ValidateMagicBytes() — validates content matches declared MIME type
PeekAndValidate() — reads minimum bytes, validates, returns combined reader
IsSupportedMIMEType() — checks if a MIME type is supported
MIMEToImageFormat() — converts MIME type to ImageFormat
ImageFormatToMIME() — converts ImageFormat to MIME string
All error sentinels (ErrUnknownFormat, ErrMagicByteMismatch, ErrNotEnoughData)
All helper functions (detectSVG, skipBOM, normalizeMIMEType)

The magic package defines its own ImageFormat type and constants to avoid circular imports (imgcache → magic for validation; magic cannot import imgcache).

Updated imports

internal/imgcache/service.go: uses magic.ValidateMagicBytes()
internal/imgcache/service_test.go: uses magic.DetectFormat() and magic.MIMEToImageFormat()

Naming

Clean package-qualified names: magic.DetectFormat(), magic.ValidateMagicBytes(), etc.
No stuttering names

Tests

Full test suite moved to internal/magic/magic_test.go (all 15 test functions preserved)
All existing tests pass unchanged
docker build . passes (includes make check: fmt, lint, tests)

## Summary Extract magic byte detection and MIME type handling from `internal/imgcache/` into a new focused `internal/magic/` package. Part of [issue #39](https://git.eeqj.de/sneak/pixa/issues/39) ## Changes ### New package: `internal/magic/` Moved the following from `internal/imgcache/magic.go`: - `MIMEType` type and constants (`MIMETypeJPEG`, `MIMETypePNG`, etc.) - `DetectFormat()` — detects image format from magic bytes - `ValidateMagicBytes()` — validates content matches declared MIME type - `PeekAndValidate()` — reads minimum bytes, validates, returns combined reader - `IsSupportedMIMEType()` — checks if a MIME type is supported - `MIMEToImageFormat()` — converts MIME type to ImageFormat - `ImageFormatToMIME()` — converts ImageFormat to MIME string - All error sentinels (`ErrUnknownFormat`, `ErrMagicByteMismatch`, `ErrNotEnoughData`) - All helper functions (`detectSVG`, `skipBOM`, `normalizeMIMEType`) The magic package defines its own `ImageFormat` type and constants to avoid circular imports (`imgcache` → `magic` for validation; `magic` cannot import `imgcache`). ### Updated imports - `internal/imgcache/service.go`: uses `magic.ValidateMagicBytes()` - `internal/imgcache/service_test.go`: uses `magic.DetectFormat()` and `magic.MIMEToImageFormat()` ### Naming - Clean package-qualified names: `magic.DetectFormat()`, `magic.ValidateMagicBytes()`, etc. - No stuttering names ### Tests - Full test suite moved to `internal/magic/magic_test.go` (all 15 test functions preserved) - All existing tests pass unchanged - `docker build .` passes (includes `make check`: fmt, lint, tests)

clawbot added 1 commit 2026-03-26 01:47:00 +01:00

refactor: extract magic byte detection into internal/magic package

check / check (push) Successful in 52s

Details

dedc729f37

Move MIMEType, DetectFormat, ValidateMagicBytes, PeekAndValidate,
IsSupportedMIMEType, MIMEToImageFormat, and ImageFormatToMIME from
internal/imgcache into a new internal/magic package.

The magic package defines its own ImageFormat type and constants to
avoid circular imports (imgcache imports magic for validation,
magic cannot import imgcache).

Update import sites in imgcache/service.go and service_test.go.

Part of issue #39.

clawbot added the needs-review label 2026-03-26 01:47:37 +01:00

clawbot commented

2026-03-26 01:50:21 +01:00

Review: PASS ✅

Clean extraction of magic byte detection into internal/magic/ package.

Checklist

Check	Result
`magic.go` moved with no logic changes	✅ Only package declaration, doc comment, and `ImageFormat` type added
`magic_test.go` moved with all tests	✅ All 13 test functions preserved, only package declaration changed
`ImageFormat` constants match originals	✅ All 6 values identical to `internal/imgcache/imgcache.go`
Import sites updated	✅ `service.go` → `magic.ValidateMagicBytes()`, `service_test.go` → `magic.DetectFormat()` / `magic.MIMEToImageFormat()`
No circular imports	✅ `internal/magic/` imports only stdlib (`bytes`, `errors`, `io`, `strings`)
No scope creep	✅ Only 4 files changed, only magic extraction
No stuttering names	✅ `magic.DetectFormat()`, `magic.ValidateMagicBytes()`, etc.
No linter/CI/test config changes	✅ `.golangci.yml`, `Makefile`, `Dockerfile`, `.gitea/workflows/` untouched
`docker build .` passes	✅ All tests pass, build succeeds

Notes

The original ImageFormat type in imgcache.go is correctly preserved (other packages like encurl, handlers, urlparser still reference imgcache.ImageFormat).
No stale references to old package-qualified names (imgcache.DetectFormat, etc.) remain anywhere in the codebase.
Two minor comment improvements: "our ImageFormat" → "an ImageFormat" — appropriate for the new standalone package context.

Part of issue #39.

## Review: PASS ✅ Clean extraction of magic byte detection into `internal/magic/` package. ### Checklist | Check | Result | |---|---| | `magic.go` moved with no logic changes | ✅ Only package declaration, doc comment, and `ImageFormat` type added | | `magic_test.go` moved with all tests | ✅ All 13 test functions preserved, only package declaration changed | | `ImageFormat` constants match originals | ✅ All 6 values identical to `internal/imgcache/imgcache.go` | | Import sites updated | ✅ `service.go` → `magic.ValidateMagicBytes()`, `service_test.go` → `magic.DetectFormat()` / `magic.MIMEToImageFormat()` | | No circular imports | ✅ `internal/magic/` imports only stdlib (`bytes`, `errors`, `io`, `strings`) | | No scope creep | ✅ Only 4 files changed, only magic extraction | | No stuttering names | ✅ `magic.DetectFormat()`, `magic.ValidateMagicBytes()`, etc. | | No linter/CI/test config changes | ✅ `.golangci.yml`, `Makefile`, `Dockerfile`, `.gitea/workflows/` untouched | | `docker build .` passes | ✅ All tests pass, build succeeds | ### Notes - The original `ImageFormat` type in `imgcache.go` is correctly preserved (other packages like `encurl`, `handlers`, `urlparser` still reference `imgcache.ImageFormat`). - No stale references to old package-qualified names (`imgcache.DetectFormat`, etc.) remain anywhere in the codebase. - Two minor comment improvements: "our ImageFormat" → "an ImageFormat" — appropriate for the new standalone package context. Part of [issue #39](https://git.eeqj.de/sneak/pixa/issues/39).

clawbot added merge-ready and removed needs-review labels 2026-03-26 01:50:44 +01:00

sneak was assigned by clawbot

2026-03-26 01:50:44 +01:00

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Reference: sneak/pixa#42