package plugin_compiler

import (
	"go/ast"
	"go/token"
	"strconv"
)

// mergeImports merges all the import declarations into the first one.
// Taken from golang.org/x/tools/ast/astutil.
func mergeImports(f *ast.File) {
	if len(f.Decls) <= 1 {
		return
	}

	// Merge all the import declarations into the first one.
	var first *ast.GenDecl
	for i := 0; i < len(f.Decls); i++ {
		decl := f.Decls[i]
		gen, ok := decl.(*ast.GenDecl)
		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
			continue
		}
		if first == nil {
			first = gen
			continue // Don't touch the first one.
		}
		// We now know there is more than one package in this import
		// declaration. Ensure that it ends up parenthesized.
		first.Lparen = first.Pos()
		// Move the imports of the other import declaration to the first one.
		for _, spec := range gen.Specs {
			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
			first.Specs = append(first.Specs, spec)
		}
		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
		i--
	}
}

// declImports reports whether gen contains an import of path.
// Taken from golang.org/x/tools/ast/astutil.
func declImports(gen *ast.GenDecl, path string) bool {
	if gen.Tok != token.IMPORT {
		return false
	}
	for _, spec := range gen.Specs {
		impspec := spec.(*ast.ImportSpec)
		if importPath(impspec) == path {
			return true
		}
	}
	return false
}

func importPath(s ast.Spec) string {
	t, err := strconv.Unquote(s.(*ast.ImportSpec).Path.Value)
	if err == nil {
		return t
	}
	return ""
}
