// Copyright 2010 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package mockgen generates mock implementations of Go interfaces.
package mockgen

// TODO: This does not support recursive embedded interfaces.
// TODO: This does not support embedding package-local interfaces in a separate file.

import (
	"bytes"
	"fmt"
	"go/format"
	"go/token"
	"log"
	"path"
	"sort"
	"strconv"
	"strings"
	"unicode"

	"github.com/otokaze/mock/mockgen/model"
)

const (
	gomockImportPath = "github.com/otokaze/mock/gomock"
)

var (
	imports, auxFiles, buildFlags, execOnly string
	progOnly                                bool
)

// Generator a generator struct.
type Generator struct {
	buf                       bytes.Buffer
	indent                    string
	MockNames                 map[string]string //may be empty
	Filename                  string            // may be empty
	SrcPackage, SrcInterfaces string            // may be empty

	packageMap map[string]string // map from import path to package name
}

func (g *Generator) p(format string, args ...interface{}) {
	fmt.Fprintf(&g.buf, g.indent+format+"\n", args...)
}

func (g *Generator) in() {
	g.indent += "\t"
}

func (g *Generator) out() {
	if len(g.indent) > 0 {
		g.indent = g.indent[0 : len(g.indent)-1]
	}
}

func removeDot(s string) string {
	if len(s) > 0 && s[len(s)-1] == '.' {
		return s[0 : len(s)-1]
	}
	return s
}

// sanitize cleans up a string to make a suitable package name.
func sanitize(s string) string {
	t := ""
	for _, r := range s {
		if t == "" {
			if unicode.IsLetter(r) || r == '_' {
				t += string(r)
				continue
			}
		} else {
			if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' {
				t += string(r)
				continue
			}
		}
		t += "_"
	}
	if t == "_" {
		t = "x"
	}
	return t
}

// Generate gen mock by pkg.
func (g *Generator) Generate(pkg *model.Package, pkgName string, outputPackagePath string) error {
	g.p("// Code generated by MockGen. DO NOT EDIT.")
	if g.Filename != "" {
		g.p("// Source: %v", g.Filename)
	} else {
		g.p("// Source: %v (interfaces: %v)", g.SrcPackage, g.SrcInterfaces)
	}
	g.p("")

	// Get all required imports, and generate unique names for them all.
	im := pkg.Imports()
	im[gomockImportPath] = true

	// Only import reflect if it's used. We only use reflect in mocked methods
	// so only import if any of the mocked interfaces have methods.
	for _, intf := range pkg.Interfaces {
		if len(intf.Methods) > 0 {
			im["reflect"] = true
			break
		}
	}

	// Sort keys to make import alias generation predictable
	sortedPaths := make([]string, len(im))
	x := 0
	for pth := range im {
		sortedPaths[x] = pth
		x++
	}
	sort.Strings(sortedPaths)

	g.packageMap = make(map[string]string, len(im))
	localNames := make(map[string]bool, len(im))
	for _, pth := range sortedPaths {
		base := sanitize(path.Base(pth))

		// Local names for an imported package can usually be the basename of the import path.
		// A couple of situations don't permit that, such as duplicate local names
		// (e.g. importing "html/template" and "text/template"), or where the basename is
		// a keyword (e.g. "foo/case").
		// try base0, base1, ...
		pkgName := base
		i := 0
		for localNames[pkgName] || token.Lookup(pkgName).IsKeyword() {
			pkgName = base + strconv.Itoa(i)
			i++
		}

		g.packageMap[pth] = pkgName
		localNames[pkgName] = true
	}

	g.p("// Package %v is a generated GoMock package.", pkgName)
	g.p("package %v", pkgName)
	g.p("")
	g.p("import (")
	g.in()
	for path, pkg := range g.packageMap {
		if path == outputPackagePath {
			continue
		}
		g.p("%v %q", pkg, path)
	}
	for _, path := range pkg.DotImports {
		g.p(". %q", path)
	}
	g.out()
	g.p(")")

	for _, intf := range pkg.Interfaces {
		if err := g.GenerateMockInterface(intf, outputPackagePath); err != nil {
			return err
		}
	}

	return nil
}

// The name of the mock type to use for the given interface identifier.
func (g *Generator) mockName(typeName string) string {
	if mockName, ok := g.MockNames[typeName]; ok {
		return mockName
	}

	return "Mock" + typeName
}

// GenerateMockInterface gen mock intf.
func (g *Generator) GenerateMockInterface(intf *model.Interface, outputPackagePath string) error {
	mockType := g.mockName(intf.Name)

	g.p("")
	g.p("// %v is a mock of %v interface", mockType, intf.Name)
	g.p("type %v struct {", mockType)
	g.in()
	g.p("ctrl     *gomock.Controller")
	g.p("recorder *%vMockRecorder", mockType)
	g.out()
	g.p("}")
	g.p("")

	g.p("// %vMockRecorder is the mock recorder for %v", mockType, mockType)
	g.p("type %vMockRecorder struct {", mockType)
	g.in()
	g.p("mock *%v", mockType)
	g.out()
	g.p("}")
	g.p("")

	// TODO: Re-enable this if we can import the interface reliably.
	//g.p("// Verify that the mock satisfies the interface at compile time.")
	//g.p("var _ %v = (*%v)(nil)", typeName, mockType)
	//g.p("")

	g.p("// New%v creates a new mock instance", mockType)
	g.p("func New%v(ctrl *gomock.Controller) *%v {", mockType, mockType)
	g.in()
	g.p("mock := &%v{ctrl: ctrl}", mockType)
	g.p("mock.recorder = &%vMockRecorder{mock}", mockType)
	g.p("return mock")
	g.out()
	g.p("}")
	g.p("")

	// XXX: possible name collision here if someone has EXPECT in their interface.
	g.p("// EXPECT returns an object that allows the caller to indicate expected use")
	g.p("func (m *%v) EXPECT() *%vMockRecorder {", mockType, mockType)
	g.in()
	g.p("return m.recorder")
	g.out()
	g.p("}")

	g.GenerateMockMethods(mockType, intf, outputPackagePath)

	return nil
}

// GenerateMockMethods gen mock methods.
func (g *Generator) GenerateMockMethods(mockType string, intf *model.Interface, pkgOverride string) {
	for _, m := range intf.Methods {
		g.p("")
		g.GenerateMockMethod(mockType, m, pkgOverride)
		g.p("")
		g.GenerateMockRecorderMethod(mockType, m)
	}
}

func makeArgString(argNames, argTypes []string) string {
	args := make([]string, len(argNames))
	for i, name := range argNames {
		// specify the type only once for consecutive args of the same type
		if i+1 < len(argTypes) && argTypes[i] == argTypes[i+1] {
			args[i] = name
		} else {
			args[i] = name + " " + argTypes[i]
		}
	}
	return strings.Join(args, ", ")
}

// GenerateMockMethod generates a mock method implementation.
// If non-empty, pkgOverride is the package in which unqualified types reside.
func (g *Generator) GenerateMockMethod(mockType string, m *model.Method, pkgOverride string) error {
	argNames := g.getArgNames(m)
	argTypes := g.getArgTypes(m, pkgOverride)
	argString := makeArgString(argNames, argTypes)

	rets := make([]string, len(m.Out))
	for i, p := range m.Out {
		rets[i] = p.Type.String(g.packageMap, pkgOverride)
	}
	retString := strings.Join(rets, ", ")
	if len(rets) > 1 {
		retString = "(" + retString + ")"
	}
	if retString != "" {
		retString = " " + retString
	}

	ia := newIdentifierAllocator(argNames)
	idRecv := ia.allocateIdentifier("m")

	g.p("// %v mocks base method", m.Name)
	g.p("func (%v *%v) %v(%v)%v {", idRecv, mockType, m.Name, argString, retString)
	g.in()

	var callArgs string
	if m.Variadic == nil {
		if len(argNames) > 0 {
			callArgs = ", " + strings.Join(argNames, ", ")
		}
	} else {
		// Non-trivial. The generated code must build a []interface{},
		// but the variadic argument may be any type.
		idVarArgs := ia.allocateIdentifier("varargs")
		idVArg := ia.allocateIdentifier("a")
		g.p("%s := []interface{}{%s}", idVarArgs, strings.Join(argNames[:len(argNames)-1], ", "))
		g.p("for _, %s := range %s {", idVArg, argNames[len(argNames)-1])
		g.in()
		g.p("%s = append(%s, %s)", idVarArgs, idVarArgs, idVArg)
		g.out()
		g.p("}")
		callArgs = ", " + idVarArgs + "..."
	}
	if len(m.Out) == 0 {
		g.p(`%v.ctrl.Call(%v, %q%v)`, idRecv, idRecv, m.Name, callArgs)
	} else {
		idRet := ia.allocateIdentifier("ret")
		g.p(`%v := %v.ctrl.Call(%v, %q%v)`, idRet, idRecv, idRecv, m.Name, callArgs)

		// Go does not allow "naked" type assertions on nil values, so we use the two-value form here.
		// The value of that is either (x.(T), true) or (Z, false), where Z is the zero value for T.
		// Happily, this coincides with the semantics we want here.
		retNames := make([]string, len(rets))
		for i, t := range rets {
			retNames[i] = ia.allocateIdentifier(fmt.Sprintf("ret%d", i))
			g.p("%s, _ := %s[%d].(%s)", retNames[i], idRet, i, t)
		}
		g.p("return " + strings.Join(retNames, ", "))
	}

	g.out()
	g.p("}")
	return nil
}

// GenerateMockRecorderMethod gen mock recorder method.
func (g *Generator) GenerateMockRecorderMethod(mockType string, m *model.Method) error {
	argNames := g.getArgNames(m)

	var argString string
	if m.Variadic == nil {
		argString = strings.Join(argNames, ", ")
	} else {
		argString = strings.Join(argNames[:len(argNames)-1], ", ")
	}
	if argString != "" {
		argString += " interface{}"
	}

	if m.Variadic != nil {
		if argString != "" {
			argString += ", "
		}
		argString += fmt.Sprintf("%s ...interface{}", argNames[len(argNames)-1])
	}

	ia := newIdentifierAllocator(argNames)
	idRecv := ia.allocateIdentifier("mr")

	g.p("// %v indicates an expected call of %v", m.Name, m.Name)
	g.p("func (%s *%vMockRecorder) %v(%v) *gomock.Call {", idRecv, mockType, m.Name, argString)
	g.in()

	var callArgs string
	if m.Variadic == nil {
		if len(argNames) > 0 {
			callArgs = ", " + strings.Join(argNames, ", ")
		}
	} else {
		if len(argNames) == 1 {
			// Easy: just use ... to push the arguments through.
			callArgs = ", " + argNames[0] + "..."
		} else {
			// Hard: create a temporary slice.
			idVarArgs := ia.allocateIdentifier("varargs")
			g.p("%s := append([]interface{}{%s}, %s...)",
				idVarArgs,
				strings.Join(argNames[:len(argNames)-1], ", "),
				argNames[len(argNames)-1])
			callArgs = ", " + idVarArgs + "..."
		}
	}
	g.p(`return %s.mock.ctrl.RecordCallWithMethodType(%s.mock, "%s", reflect.TypeOf((*%s)(nil).%s)%s)`, idRecv, idRecv, m.Name, mockType, m.Name, callArgs)

	g.out()
	g.p("}")
	return nil
}

func (g *Generator) getArgNames(m *model.Method) []string {
	argNames := make([]string, len(m.In))
	for i, p := range m.In {
		name := p.Name
		if name == "" {
			name = fmt.Sprintf("arg%d", i)
		}
		argNames[i] = name
	}
	if m.Variadic != nil {
		name := m.Variadic.Name
		if name == "" {
			name = fmt.Sprintf("arg%d", len(m.In))
		}
		argNames = append(argNames, name)
	}
	return argNames
}

func (g *Generator) getArgTypes(m *model.Method, pkgOverride string) []string {
	argTypes := make([]string, len(m.In))
	for i, p := range m.In {
		argTypes[i] = p.Type.String(g.packageMap, pkgOverride)
	}
	if m.Variadic != nil {
		argTypes = append(argTypes, "..."+m.Variadic.Type.String(g.packageMap, pkgOverride))
	}
	return argTypes
}

type identifierAllocator map[string]struct{}

func newIdentifierAllocator(taken []string) identifierAllocator {
	a := make(identifierAllocator, len(taken))
	for _, s := range taken {
		a[s] = struct{}{}
	}
	return a
}

func (o identifierAllocator) allocateIdentifier(want string) string {
	id := want
	for i := 2; ; i++ {
		if _, ok := o[id]; !ok {
			o[id] = struct{}{}
			return id
		}
		id = want + "_" + strconv.Itoa(i)
	}
}

// Output returns the generator's output, formatted in the standard Go style.
func (g *Generator) Output() []byte {
	src, err := format.Source(g.buf.Bytes())
	if err != nil {
		log.Fatalf("Failed to format generated source code: %s\n%s", err, g.buf.String())
	}
	return src
}