// Copyright 2015 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 irutil

// This file defines utility functions for constructing programs in IR form.

import (
	"go/ast"
	"go/token"
	"go/types"

	"golang.org/x/tools/go/loader"
	"golang.org/x/tools/go/packages"
	"honnef.co/go/tools/ir"
)

type Options struct {
	// Which function, if any, to print in HTML form
	PrintFunc string
}

// Packages creates an IR program for a set of packages.
//
// The packages must have been loaded from source syntax using the
// golang.org/x/tools/go/packages.Load function in LoadSyntax or
// LoadAllSyntax mode.
//
// Packages creates an IR package for each well-typed package in the
// initial list, plus all their dependencies. The resulting list of
// packages corresponds to the list of initial packages, and may contain
// a nil if IR code could not be constructed for the corresponding initial
// package due to type errors.
//
// Code for bodies of functions is not built until Build is called on
// the resulting Program. IR code is constructed only for the initial
// packages with well-typed syntax trees.
//
// The mode parameter controls diagnostics and checking during IR construction.
//
func Packages(initial []*packages.Package, mode ir.BuilderMode, opts *Options) (*ir.Program, []*ir.Package) {
	return doPackages(initial, mode, false, opts)
}

// AllPackages creates an IR program for a set of packages plus all
// their dependencies.
//
// The packages must have been loaded from source syntax using the
// golang.org/x/tools/go/packages.Load function in LoadAllSyntax mode.
//
// AllPackages creates an IR package for each well-typed package in the
// initial list, plus all their dependencies. The resulting list of
// packages corresponds to the list of initial packages, and may contain
// a nil if IR code could not be constructed for the corresponding
// initial package due to type errors.
//
// Code for bodies of functions is not built until Build is called on
// the resulting Program. IR code is constructed for all packages with
// well-typed syntax trees.
//
// The mode parameter controls diagnostics and checking during IR construction.
//
func AllPackages(initial []*packages.Package, mode ir.BuilderMode, opts *Options) (*ir.Program, []*ir.Package) {
	return doPackages(initial, mode, true, opts)
}

func doPackages(initial []*packages.Package, mode ir.BuilderMode, deps bool, opts *Options) (*ir.Program, []*ir.Package) {

	var fset *token.FileSet
	if len(initial) > 0 {
		fset = initial[0].Fset
	}

	prog := ir.NewProgram(fset, mode)
	if opts != nil {
		prog.PrintFunc = opts.PrintFunc
	}

	isInitial := make(map[*packages.Package]bool, len(initial))
	for _, p := range initial {
		isInitial[p] = true
	}

	irmap := make(map[*packages.Package]*ir.Package)
	packages.Visit(initial, nil, func(p *packages.Package) {
		if p.Types != nil && !p.IllTyped {
			var files []*ast.File
			if deps || isInitial[p] {
				files = p.Syntax
			}
			irmap[p] = prog.CreatePackage(p.Types, files, p.TypesInfo, true)
		}
	})

	var irpkgs []*ir.Package
	for _, p := range initial {
		irpkgs = append(irpkgs, irmap[p]) // may be nil
	}
	return prog, irpkgs
}

// CreateProgram returns a new program in IR form, given a program
// loaded from source.  An IR package is created for each transitively
// error-free package of lprog.
//
// Code for bodies of functions is not built until Build is called
// on the result.
//
// The mode parameter controls diagnostics and checking during IR construction.
//
// Deprecated: use golang.org/x/tools/go/packages and the Packages
// function instead; see ir.ExampleLoadPackages.
//
func CreateProgram(lprog *loader.Program, mode ir.BuilderMode) *ir.Program {
	prog := ir.NewProgram(lprog.Fset, mode)

	for _, info := range lprog.AllPackages {
		if info.TransitivelyErrorFree {
			prog.CreatePackage(info.Pkg, info.Files, &info.Info, info.Importable)
		}
	}

	return prog
}

// BuildPackage builds an IR program with IR for a single package.
//
// It populates pkg by type-checking the specified file ASTs.  All
// dependencies are loaded using the importer specified by tc, which
// typically loads compiler export data; IR code cannot be built for
// those packages.  BuildPackage then constructs an ir.Program with all
// dependency packages created, and builds and returns the IR package
// corresponding to pkg.
//
// The caller must have set pkg.Path() to the import path.
//
// The operation fails if there were any type-checking or import errors.
//
// See ../ir/example_test.go for an example.
//
func BuildPackage(tc *types.Config, fset *token.FileSet, pkg *types.Package, files []*ast.File, mode ir.BuilderMode) (*ir.Package, *types.Info, error) {
	if fset == nil {
		panic("no token.FileSet")
	}
	if pkg.Path() == "" {
		panic("package has no import path")
	}

	info := &types.Info{
		Types:      make(map[ast.Expr]types.TypeAndValue),
		Defs:       make(map[*ast.Ident]types.Object),
		Uses:       make(map[*ast.Ident]types.Object),
		Implicits:  make(map[ast.Node]types.Object),
		Scopes:     make(map[ast.Node]*types.Scope),
		Selections: make(map[*ast.SelectorExpr]*types.Selection),
	}
	if err := types.NewChecker(tc, fset, pkg, info).Files(files); err != nil {
		return nil, nil, err
	}

	prog := ir.NewProgram(fset, mode)

	// Create IR packages for all imports.
	// Order is not significant.
	created := make(map[*types.Package]bool)
	var createAll func(pkgs []*types.Package)
	createAll = func(pkgs []*types.Package) {
		for _, p := range pkgs {
			if !created[p] {
				created[p] = true
				prog.CreatePackage(p, nil, nil, true)
				createAll(p.Imports())
			}
		}
	}
	createAll(pkg.Imports())

	// Create and build the primary package.
	irpkg := prog.CreatePackage(pkg, files, info, false)
	irpkg.Build()
	return irpkg, info, nil
}