// Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package fxreflect

import (
	"fmt"
	"net/url"
	"reflect"
	"regexp"
	"runtime"
	"strings"

	"go.uber.org/dig"
)

// Match from beginning of the line until the first `vendor/` (non-greedy)
var vendorRe = regexp.MustCompile("^.*?/vendor/")

// ReturnTypes takes a func and returns a slice of string'd types.
func ReturnTypes(t interface{}) []string {
	if reflect.TypeOf(t).Kind() != reflect.Func {
		// Invalid provide, will be logged as an error.
		return []string{}
	}

	rtypes := []string{}
	ft := reflect.ValueOf(t).Type()

	for i := 0; i < ft.NumOut(); i++ {
		t := ft.Out(i)

		traverseOuts(key{t: t}, func(s string) {
			rtypes = append(rtypes, s)
		})
	}

	return rtypes
}

type key struct {
	t    reflect.Type
	name string
}

func (k *key) String() string {
	if k.name != "" {
		return fmt.Sprintf("%v:%s", k.t, k.name)
	}
	return k.t.String()
}

func traverseOuts(k key, f func(s string)) {
	// skip errors
	if isErr(k.t) {
		return
	}

	// call function on non-Out types
	if dig.IsOut(k.t) {
		// keep recursing down on field members in case they are ins
		for i := 0; i < k.t.NumField(); i++ {
			field := k.t.Field(i)
			ft := field.Type

			if field.PkgPath != "" {
				continue // skip private fields
			}

			// keep recursing to traverse all the embedded objects
			k := key{
				t:    ft,
				name: field.Tag.Get("name"),
			}
			traverseOuts(k, f)
		}

		return
	}

	f(k.String())
}

// sanitize makes the function name suitable for logging display. It removes
// url-encoded elements from the `dot.git` package names and shortens the
// vendored paths.
func sanitize(function string) string {
	// Use the stdlib to un-escape any package import paths which can happen
	// in the case of the "dot-git" postfix. Seems like a bug in stdlib =/
	if unescaped, err := url.QueryUnescape(function); err == nil {
		function = unescaped
	}

	// strip everything prior to the vendor
	return vendorRe.ReplaceAllString(function, "vendor/")
}

// Caller returns the formatted calling func name
func Caller() string {
	return CallerStack(1, 0).CallerName()
}

// FuncName returns a funcs formatted name
func FuncName(fn interface{}) string {
	fnV := reflect.ValueOf(fn)
	if fnV.Kind() != reflect.Func {
		return fmt.Sprint(fn)
	}

	function := runtime.FuncForPC(fnV.Pointer()).Name()
	return fmt.Sprintf("%s()", sanitize(function))
}

func isErr(t reflect.Type) bool {
	errInterface := reflect.TypeOf((*error)(nil)).Elem()
	return t.Implements(errInterface)
}

// Ascend the call stack until we leave the Fx production code. This allows us
// to avoid hard-coding a frame skip, which makes this code work well even
// when it's wrapped.
func shouldIgnoreFrame(f Frame) bool {
	// Treat test files as leafs.
	if strings.Contains(f.File, "_test.go") {
		return false
	}

	// The unique, fully-qualified name for all functions begins with
	// "{{importPath}}.". We'll ignore Fx and its subpackages.
	s := strings.TrimPrefix(f.Function, "go.uber.org/fx")
	if len(s) > 0 && s[0] == '.' || s[0] == '/' {
		// We want to match,
		//   go.uber.org/fx.Foo
		//   go.uber.org/fx/something.Foo
		// But not, go.uber.org/fxfoo
		return true
	}

	return false
}