package routing

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

// forbiddenImportPrefixes are the packages the pure routing model must never
// pull into its build OR test graph (SPEC-002 §5, the purity assertion).
var forbiddenImportPrefixes = []string{
	"net/http",
	"database/sql",
}

// TestPurityNoHTTPOrDB makes the purity assertion real: it parses every .go
// file in this package — implementation and tests — and fails if any of them
// imports an HTTP or DB package.
func TestPurityNoHTTPOrDB(t *testing.T) {
	_, thisFile, _, ok := runtime.Caller(0)
	if !ok {
		t.Fatal("runtime.Caller failed")
	}
	dir := filepath.Dir(thisFile)

	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatalf("ReadDir(%s): %v", dir, err)
	}

	fset := token.NewFileSet()
	checked := 0
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".go") {
			continue
		}
		file, err := parser.ParseFile(fset, filepath.Join(dir, e.Name()), nil, parser.ImportsOnly)
		if err != nil {
			t.Fatalf("parse %s: %v", e.Name(), err)
		}
		checked++
		for _, imp := range file.Imports {
			pkg := strings.Trim(imp.Path.Value, `"`)
			for _, bad := range forbiddenImportPrefixes {
				if pkg == bad || strings.HasPrefix(pkg, bad+"/") {
					t.Errorf("%s imports forbidden package %q (the routing model must be pure)", e.Name(), pkg)
				}
			}
		}
	}

	if checked == 0 {
		t.Fatal("purity check found no .go files to inspect")
	}
}