package infra

import (
	"os"
	"path/filepath"
)

// AppLocationViolation describes an artefact found in a language-specific
// directory where it does not belong (e.g. cpp/apps/, python/analysis/).
type AppLocationViolation struct {
	Path string // relative from repoRoot (e.g. "cpp/apps/foo")
	Kind string // "app" | "analysis"
	Lang string // "cpp" | "python" | "bash" | "frontend"
}

// AuditAppLocation scans language-specific directories that must NOT contain
// artefacts (apps or analyses) and returns every subdirectory that holds an
// app.md or analysis.md manifest.
//
// Prohibited directories checked:
//   - cpp/apps/, cpp/analysis/
//   - python/apps/, python/analysis/
//   - bash/apps/, bash/analysis/
//   - frontend/apps/, frontend/analysis/
//
// If a prohibited directory does not exist it is silently skipped.
// Artefacts under the canonical apps/ and analysis/ roots are not flagged.
func AuditAppLocation(repoRoot string) ([]AppLocationViolation, error) {
	type candidate struct {
		lang string
		kind string
		dir  string // relative dir inside repoRoot
	}

	candidates := []candidate{
		{lang: "cpp", kind: "app", dir: "cpp/apps"},
		{lang: "cpp", kind: "analysis", dir: "cpp/analysis"},
		{lang: "python", kind: "app", dir: "python/apps"},
		{lang: "python", kind: "analysis", dir: "python/analysis"},
		{lang: "bash", kind: "app", dir: "bash/apps"},
		{lang: "bash", kind: "analysis", dir: "bash/analysis"},
		{lang: "frontend", kind: "app", dir: "frontend/apps"},
		{lang: "frontend", kind: "analysis", dir: "frontend/analysis"},
	}

	manifest := map[string]string{
		"app":      "app.md",
		"analysis": "analysis.md",
	}

	var out []AppLocationViolation

	for _, c := range candidates {
		absDir := filepath.Join(repoRoot, c.dir)
		entries, err := os.ReadDir(absDir)
		if err != nil {
			if os.IsNotExist(err) {
				continue
			}
			return nil, err
		}

		mf := manifest[c.kind]
		for _, e := range entries {
			if !e.IsDir() {
				continue
			}
			mdPath := filepath.Join(absDir, e.Name(), mf)
			if _, err := os.Stat(mdPath); err == nil {
				out = append(out, AppLocationViolation{
					Path: filepath.Join(c.dir, e.Name()),
					Kind: c.kind,
					Lang: c.lang,
				})
			}
		}
	}

	return out, nil
}