---
phase: 06-output-reporting
plan: 01
subsystem: pkg/output
tags: [output, formatter, registry, tty, colors, refactor]
requirements: [OUT-01, OUT-06]
dependency-graph:
  requires: [pkg/engine.Finding]
  provides:
    - "output.Formatter interface"
    - "output.Options struct"
    - "output.Registry (Register/Get/Names/ErrUnknownFormat)"
    - "output.TableFormatter"
    - "output.IsTTY / output.ColorsEnabled"
  affects: [cmd/scan.go PrintFindings wrapper]
tech-stack:
  added:
    - "github.com/mattn/go-isatty (promoted from indirect to direct)"
  patterns:
    - "Registry via init()-registered formatters"
    - "TTY-aware color stripping using zero-value lipgloss.Style"
    - "Deprecated wrapper (PrintFindings) delegating to new interface"
key-files:
  created:
    - pkg/output/formatter.go
    - pkg/output/formatter_test.go
    - pkg/output/colors.go
    - pkg/output/colors_test.go
  modified:
    - pkg/output/table.go
    - pkg/output/table_test.go
    - go.mod
decisions:
  - "Registry is unguarded: all registration happens at init() before main."
  - "newTableStyles(false) returns zero lipgloss.Style values — lipgloss passes text through verbatim, guaranteeing no ANSI escapes on non-TTY writers."
  - "PrintFindings(findings, unmask) kept as backward-compat wrapper so cmd/scan.go still compiles unchanged until Plan 06 (scan flag wiring)."
  - "ColorsEnabled honours NO_COLOR (https://no-color.org/) before the TTY check."
metrics:
  duration: ~8m
  completed: 2026-04-05
  tasks: 2
  commits: 3
---

# Phase 06 Plan 01: Formatter Interface + TableFormatter Refactor Summary

Established the `output.Formatter` interface, a name-keyed registry, and TTY-aware color detection, then refactored the existing colored-table output to implement `Formatter` and register itself as `"table"`. This is the foundation every other Phase 6 formatter (JSON, SARIF, CSV) will plug into.

## What Was Built

### 1. Formatter interface + registry (`pkg/output/formatter.go`)

- `Formatter` interface: `Format(findings []engine.Finding, w io.Writer, opts Options) error`
- `Options` struct: `{ Unmask, ToolName, ToolVersion }`
- `Register(name, f)` — called from `init()` functions
- `Get(name)` — returns `ErrUnknownFormat` wrapped via `fmt.Errorf("%w: %q", ...)`
- `Names()` — sorted list for `--output` help text
- `ErrUnknownFormat` sentinel, discoverable via `errors.Is`

### 2. TTY detection (`pkg/output/colors.go`)

- `IsTTY(*os.File) bool` — wraps `isatty.IsTerminal` + `isatty.IsCygwinTerminal`, nil-safe
- `ColorsEnabled(io.Writer) bool` — returns false when `NO_COLOR` is set, when writer is not an `*os.File`, or when the file is not a TTY
- Promoted `github.com/mattn/go-isatty v0.0.20` from indirect (via lipgloss) to a direct dependency in `go.mod`

### 3. TableFormatter refactor (`pkg/output/table.go`)

- `TableFormatter struct{}` implements `Formatter`, registered under `"table"` in `init()`
- Writes to the caller-supplied `io.Writer` (no more hardcoded `os.Stdout`)
- New `tableStyles` bundle + `newTableStyles(colored bool)` factory — when `colored==false` every style is a zero `lipgloss.Style`, which renders text verbatim with zero ANSI escapes
- Preserves the exact layout from Phase 5: PROVIDER/KEY/CONFIDENCE/SOURCE/LINE columns plus optional VERIFY column, indented sorted metadata line, footer `"N key(s) found."`
- Respects `Options.Unmask` to toggle between `KeyMasked` and `KeyValue`
- `PrintFindings(findings, unmask)` retained as a deprecated thin wrapper that delegates to `TableFormatter{}.Format(..., os.Stdout, Options{Unmask: unmask})` — keeps `cmd/scan.go` compiling untouched until Plan 06.

## Tests

All green on `go test ./pkg/output/... -count=1`:

- **formatter_test.go**: `Register/Get` round-trip, `Get` unknown → `ErrUnknownFormat` via `errors.Is`, `Names()` sort ordering, `Options` zero-value defaults.
- **colors_test.go**: `ColorsEnabled(&bytes.Buffer{})==false`, `NO_COLOR=1` forces false, typed-nil writer does not panic, `IsTTY(nil)==false`.
- **table_test.go (new)**:
  - Empty slice → exact `"No API keys found.\n"`
  - Two findings (one verified) written to `bytes.Buffer` → output contains no `\x1b[` escapes, includes `VERIFY` column and `"2 key(s) found."` footer
  - Unverified-only header does NOT contain `VERIFY`
  - Verified row shows `live`
  - Unmask=false renders `KeyMasked`; Unmask=true renders `KeyValue`
  - VerifyMetadata `{z:1, a:2}` renders `a: 2` before `z: 1`
  - `Get("table")` returns a `TableFormatter`
- **table_test.go (legacy)**: `PrintFindings` stdout-capture tests still pass (backward compat preserved).

Full project suite (`go test ./...`) green: cmd, engine, engine/sources, legal, output, providers, storage, verify.

## Key Decisions

1. **Registry is unguarded.** All `Register` calls happen from package `init()` before `main`, which Go runs sequentially. Adding a mutex would be dead weight.

2. **Plain styles via zero lipgloss.Style.** Instead of conditionally calling different render functions, `newTableStyles(false)` returns `lipgloss.NewStyle()` for every field. A zero `lipgloss.Style` passes text through verbatim, so the same `fmt.Fprintf(... style.header.Render("PROVIDER") ...)` code path produces colored output on a TTY and plain output to a `bytes.Buffer`.

3. **Backward-compat wrapper.** `PrintFindings` stays so `cmd/scan.go` compiles without edits. Plan 06 will replace it with a registry lookup when wiring the `--output` flag. Deprecated comment in place.

4. **NO_COLOR precedence.** `ColorsEnabled` checks `NO_COLOR` before the TTY check, matching the https://no-color.org/ spec ("should check for a NO_COLOR environment variable that, when present (regardless of its value), prevents the addition of ANSI color").

## Deviations from Plan

None — plan executed exactly as written.

## Commits

| Commit  | Type | Message                                                    |
| ------- | ---- | ---------------------------------------------------------- |
| 291c97e | feat | add Formatter interface, Registry, and TTY color detection |
| 8c37252 | test | add failing tests for TableFormatter refactor              |
| 8e4db5d | feat | refactor table output into TableFormatter                  |

## Foundation for Next Plans

- **Plan 02** (JSON + SARIF): create `pkg/output/json.go` and `pkg/output/sarif.go`, each with an `init()` calling `Register`. Implement `Format` against `[]engine.Finding`. Use `Options.ToolName`/`Options.ToolVersion` for SARIF `tool.driver` metadata.
- **Plan 03** (CSV): identical pattern with `encoding/csv`.
- **Plan 06** (scan wiring): replace `output.PrintFindings(findings, unmask)` in `cmd/scan.go` with `output.Get(flag)` + `f.Format(findings, os.Stdout, Options{Unmask: unmask, ToolName: "keyhunter", ToolVersion: version})`.

## Self-Check: PASSED

- pkg/output/formatter.go — FOUND
- pkg/output/formatter_test.go — FOUND
- pkg/output/colors.go — FOUND
- pkg/output/colors_test.go — FOUND
- pkg/output/table.go — modified (TableFormatter present, `Register("table", ...)` in init)
- pkg/output/table_test.go — modified (TableFormatter test block present)
- go.mod — `github.com/mattn/go-isatty v0.0.20` in direct require block
- Commits 291c97e, 8c37252, 8e4db5d — FOUND in `git log`
- `go build ./...` — succeeds
- `go test ./pkg/output/... -count=1` — PASS
- `go test ./...` — PASS
