// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package typesutil

import (
	"go/ast"
	"go/types"
)

// ImportedPkgName returns the PkgName object declared by an ImportSpec.
// TODO(adonovan): use go1.22's Info.PkgNameOf.
func ImportedPkgName(info *types.Info, imp *ast.ImportSpec) (*types.PkgName, bool) {
	var obj types.Object
	if imp.Name != nil {
		obj = info.Defs[imp.Name]
	} else {
		obj = info.Implicits[imp]
	}
	pkgname, ok := obj.(*types.PkgName)
	return pkgname, ok
}

// FileQualifier returns a [types.Qualifier] function that qualifies
// imported symbols appropriately based on the import environment of a
// given file.
func FileQualifier(f *ast.File, pkg *types.Package, info *types.Info) types.Qualifier {
	// Construct mapping of import paths to their defined or implicit names.
	imports := make(map[*types.Package]string)
	for _, imp := range f.Imports {
		if pkgname, ok := ImportedPkgName(info, imp); ok {
			imports[pkgname.Imported()] = pkgname.Name()
		}
	}
	// Define qualifier to replace full package paths with names of the imports.
	return func(p *types.Package) string {
		if p == pkg {
			return ""
		}
		if name, ok := imports[p]; ok {
			if name == "." {
				return ""
			}
			return name
		}
		return p.Name()
	}
}