// Package guards turns rules that used to live only as prose in
// AGENTS.md into tests. CARLOS's own rule for this: "A guard a shell
// step can satisfy is a guard a shell step can be wrong about — put
// guards inside the test binary." So these run as part of `go test
// ./...`, not as separate shell greps that a CI step could get subtly
// wrong (or that a shell rewrite could quietly stop running).
//
// This file holds the shared plumbing (repo-root discovery, file
// walking, import parsing) that every rule's test file uses. It carries
// no Test functions of its own.
package guards

import (
	"go/parser"
	"go/token"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"testing"
)

// module is the module path declared in this repo's go.mod. Used to
// confirm repoRoot found the right go.mod, not some unrelated one on a
// parent path (e.g. if the worktree lives under another Go module).
const module = "amadan.net/oficina/sheets"

// repoRoot locates the module root by walking up from this source
// file's own location (via runtime.Caller), not from the working
// directory. `go test ./...` runs every package's tests with that
// package's own directory as cwd, so cwd is not a reliable anchor —
// runtime.Caller(0) always points back to this file, wherever it was
// invoked from.
func repoRoot(t *testing.T) string {
	t.Helper()
	_, thisFile, _, ok := runtime.Caller(0)
	if !ok {
		t.Fatal("guards: runtime.Caller(0) failed")
	}
	dir := filepath.Dir(thisFile)
	for {
		if b, err := os.ReadFile(filepath.Join(dir, "go.mod")); err == nil {
			if strings.Contains(string(b), "module "+module+"\n") {
				return dir
			}
		}
		parent := filepath.Dir(dir)
		if parent == dir {
			t.Fatalf("guards: no go.mod for module %q found above %s", module, filepath.Dir(thisFile))
		}
		dir = parent
	}
}

// skipDirs names directories goFiles never descends into: version
// control, dependency/vendor trees, and dotfiles-style tooling
// directories that hold no Go source of ours.
func skipDir(name string) bool {
	if strings.HasPrefix(name, ".") {
		return true
	}
	switch name {
	case "vendor", "node_modules", "testdata":
		return true
	}
	return false
}

// goFiles returns the repo-relative path of every *.go file under root.
func goFiles(t *testing.T, root string) []string {
	t.Helper()
	var files []string
	err := filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			if path != root && skipDir(d.Name()) {
				return filepath.SkipDir
			}
			return nil
		}
		if strings.HasSuffix(path, ".go") {
			files = append(files, path)
		}
		return nil
	})
	if err != nil {
		t.Fatalf("guards: walk %s: %v", root, err)
	}
	return files
}

// relPath is filepath.Rel with the guards-package error-handling
// boilerplate folded in, since every rule needs a repo-relative path
// for its failure messages.
func relPath(t *testing.T, root, path string) string {
	t.Helper()
	rel, err := filepath.Rel(root, path)
	if err != nil {
		t.Fatalf("guards: rel %s: %v", path, err)
	}
	return filepath.ToSlash(rel)
}

// fileImports returns the import paths a Go source file declares. It
// parses in ImportsOnly mode — the cheapest mode that still sees the
// import block — so walking every file in the tree on every test run
// stays fast.
func fileImports(t *testing.T, path string) []string {
	t.Helper()
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, path, nil, parser.ImportsOnly)
	if err != nil {
		t.Fatalf("guards: parse %s: %v", path, err)
	}
	imports := make([]string, 0, len(f.Imports))
	for _, imp := range f.Imports {
		p, err := strconv.Unquote(imp.Path.Value)
		if err != nil {
			t.Fatalf("guards: unquote import in %s: %v", path, err)
		}
		imports = append(imports, p)
	}
	return imports
}

// inTree reports whether rel — a repo-relative file path — lives inside
// the directory tree rooted at dir (dir itself, or any subdirectory of
// it, at any depth). Used instead of comparing filepath.Dir(rel) == dir
// so a rule means "this whole package tree" and not just "files whose
// immediate parent happens to match" — a future subpackage (e.g.
// calc/functions) must inherit the rule, not silently fall outside it.
func inTree(rel, dir string) bool {
	return strings.HasPrefix(rel, dir+"/")
}

// importUnder reports whether imp is base itself, or an import path
// nested under base (base plus "/something"). Used instead of plain
// equality so a forbidden import stays forbidden if it grows
// subpackages later (e.g. a future .../store/schema), rather than the
// check silently narrowing to just the package's root import path.
func importUnder(imp, base string) bool {
	return imp == base || strings.HasPrefix(imp, base+"/")
}