package helper

import (
	"crypto/sha512"
	"fmt"
	"path/filepath"
	"reflect"
	"regexp"
	"strings"
	"time"

	multierror "github.com/hashicorp/go-multierror"
	"github.com/hashicorp/hcl/hcl/ast"
)

// validUUID is used to check if a given string looks like a UUID
var validUUID = regexp.MustCompile(`(?i)^[\da-f]{8}-[\da-f]{4}-[\da-f]{4}-[\da-f]{4}-[\da-f]{12}$`)

// validInterpVarKey matches valid dotted variable names for interpolation. The
// string must begin with one or more non-dot characters which may be followed
// by sequences containing a dot followed by a one or more non-dot characters.
var validInterpVarKey = regexp.MustCompile(`^[^.]+(\.[^.]+)*$`)

// invalidFilename is the minimum set of characters which must be removed or
// replaced to produce a valid filename
var invalidFilename = regexp.MustCompile(`[/\\<>:"|?*]`)

// invalidFilenameNonASCII = invalidFilename plus all non-ASCII characters
var invalidFilenameNonASCII = regexp.MustCompile(`[[:^ascii:]/\\<>:"|?*]`)

// invalidFilenameStrict = invalidFilename plus additional punctuation
var invalidFilenameStrict = regexp.MustCompile(`[/\\<>:"|?*$()+=[\];#@~,&']`)

// IsUUID returns true if the given string is a valid UUID.
func IsUUID(str string) bool {
	const uuidLen = 36
	if len(str) != uuidLen {
		return false
	}

	return validUUID.MatchString(str)
}

// IsValidInterpVariable returns true if a valid dotted variable names for
// interpolation. The string must begin with one or more non-dot characters
// which may be followed by sequences containing a dot followed by a one or more
// non-dot characters.
func IsValidInterpVariable(str string) bool {
	return validInterpVarKey.MatchString(str)
}

// HashUUID takes an input UUID and returns a hashed version of the UUID to
// ensure it is well distributed.
func HashUUID(input string) (output string, hashed bool) {
	if !IsUUID(input) {
		return "", false
	}

	// Hash the input
	buf := sha512.Sum512([]byte(input))
	output = fmt.Sprintf("%08x-%04x-%04x-%04x-%12x",
		buf[0:4],
		buf[4:6],
		buf[6:8],
		buf[8:10],
		buf[10:16])

	return output, true
}

// BoolToPtr returns the pointer to a boolean.
func BoolToPtr(b bool) *bool {
	return &b
}

// IntToPtr returns the pointer to an int
func IntToPtr(i int) *int {
	return &i
}

// Int8ToPtr returns the pointer to an int8
func Int8ToPtr(i int8) *int8 {
	return &i
}

// Int32ToPtr returns the pointer to an int32
func Int32ToPtr(i int32) *int32 {
	return &i
}

// Int64ToPtr returns the pointer to an int64
func Int64ToPtr(i int64) *int64 {
	return &i
}

// Uint64ToPtr returns the pointer to an uint64
func Uint64ToPtr(u uint64) *uint64 {
	return &u
}

// UintToPtr returns the pointer to an uint
func UintToPtr(u uint) *uint {
	return &u
}

// StringToPtr returns the pointer to a string
func StringToPtr(str string) *string {
	return &str
}

// TimeToPtr returns the pointer to a time.Duration.
func TimeToPtr(t time.Duration) *time.Duration {
	return &t
}

// CompareTimePtrs return true if a is the same as b.
func CompareTimePtrs(a, b *time.Duration) bool {
	if a == nil || b == nil {
		return a == b
	}
	return *a == *b
}

// Float64ToPtr returns the pointer to an float64
func Float64ToPtr(f float64) *float64 {
	return &f
}

func IntMin(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func IntMax(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func Uint64Max(a, b uint64) uint64 {
	if a > b {
		return a
	}
	return b
}

// MapStringStringSliceValueSet returns the set of values in a map[string][]string
func MapStringStringSliceValueSet(m map[string][]string) []string {
	set := make(map[string]struct{})
	for _, slice := range m {
		for _, v := range slice {
			set[v] = struct{}{}
		}
	}

	flat := make([]string, 0, len(set))
	for k := range set {
		flat = append(flat, k)
	}
	return flat
}

func SliceStringToSet(s []string) map[string]struct{} {
	m := make(map[string]struct{}, (len(s)+1)/2)
	for _, k := range s {
		m[k] = struct{}{}
	}
	return m
}

// SliceStringIsSubset returns whether the smaller set of strings is a subset of
// the larger. If the smaller slice is not a subset, the offending elements are
// returned.
func SliceStringIsSubset(larger, smaller []string) (bool, []string) {
	largerSet := make(map[string]struct{}, len(larger))
	for _, l := range larger {
		largerSet[l] = struct{}{}
	}

	subset := true
	var offending []string
	for _, s := range smaller {
		if _, ok := largerSet[s]; !ok {
			subset = false
			offending = append(offending, s)
		}
	}

	return subset, offending
}

// SliceStringContains returns whether item exists at least once in list.
func SliceStringContains(list []string, item string) bool {
	for _, s := range list {
		if s == item {
			return true
		}
	}
	return false
}

// SliceStringHasPrefix returns true if any string in list starts with prefix
func SliceStringHasPrefix(list []string, prefix string) bool {
	for _, s := range list {
		if strings.HasPrefix(s, prefix) {
			return true
		}
	}
	return false
}

// StringHasPrefixInSlice returns true if string starts with any prefix in list
func StringHasPrefixInSlice(s string, prefixes []string) bool {
	for _, prefix := range prefixes {
		if strings.HasPrefix(s, prefix) {
			return true
		}
	}
	return false
}

func SliceSetDisjoint(first, second []string) (bool, []string) {
	contained := make(map[string]struct{}, len(first))
	for _, k := range first {
		contained[k] = struct{}{}
	}

	offending := make(map[string]struct{})
	for _, k := range second {
		if _, ok := contained[k]; ok {
			offending[k] = struct{}{}
		}
	}

	if len(offending) == 0 {
		return true, nil
	}

	flattened := make([]string, 0, len(offending))
	for k := range offending {
		flattened = append(flattened, k)
	}
	return false, flattened
}

// CompareSliceSetString returns true if the slices contain the same strings.
// Order is ignored. The slice may be copied but is never altered. The slice is
// assumed to be a set. Multiple instances of an entry are treated the same as
// a single instance.
func CompareSliceSetString(a, b []string) bool {
	n := len(a)
	if n != len(b) {
		return false
	}

	// Copy a into a map and compare b against it
	amap := make(map[string]struct{}, n)
	for i := range a {
		amap[a[i]] = struct{}{}
	}

	for i := range b {
		if _, ok := amap[b[i]]; !ok {
			return false
		}
	}

	return true
}

// CompareMapStringString returns true if the maps are equivalent. A nil and
// empty map are considered not equal.
func CompareMapStringString(a, b map[string]string) bool {
	if a == nil || b == nil {
		return a == nil && b == nil
	}

	if len(a) != len(b) {
		return false
	}

	for k, v := range a {
		v2, ok := b[k]
		if !ok {
			return false
		}
		if v != v2 {
			return false
		}
	}

	// Already compared all known values in a so only test that keys from b
	// exist in a
	for k := range b {
		if _, ok := a[k]; !ok {
			return false
		}
	}

	return true
}

// Below is helpers for copying generic structures.

func CopyMapStringString(m map[string]string) map[string]string {
	l := len(m)
	if l == 0 {
		return nil
	}

	c := make(map[string]string, l)
	for k, v := range m {
		c[k] = v
	}
	return c
}

func CopyMapStringStruct(m map[string]struct{}) map[string]struct{} {
	l := len(m)
	if l == 0 {
		return nil
	}

	c := make(map[string]struct{}, l)
	for k := range m {
		c[k] = struct{}{}
	}
	return c
}

func CopyMapStringInterface(m map[string]interface{}) map[string]interface{} {
	l := len(m)
	if l == 0 {
		return nil
	}

	c := make(map[string]interface{}, l)
	for k, v := range m {
		c[k] = v
	}
	return c
}

func CopyMapStringInt(m map[string]int) map[string]int {
	l := len(m)
	if l == 0 {
		return nil
	}

	c := make(map[string]int, l)
	for k, v := range m {
		c[k] = v
	}
	return c
}

func CopyMapStringFloat64(m map[string]float64) map[string]float64 {
	l := len(m)
	if l == 0 {
		return nil
	}

	c := make(map[string]float64, l)
	for k, v := range m {
		c[k] = v
	}
	return c
}

// CopyMapStringSliceString copies a map of strings to string slices such as
// http.Header
func CopyMapStringSliceString(m map[string][]string) map[string][]string {
	l := len(m)
	if l == 0 {
		return nil
	}

	c := make(map[string][]string, l)
	for k, v := range m {
		c[k] = CopySliceString(v)
	}
	return c
}

func CopySliceString(s []string) []string {
	l := len(s)
	if l == 0 {
		return nil
	}

	c := make([]string, l)
	copy(c, s)
	return c
}

func CopySliceInt(s []int) []int {
	l := len(s)
	if l == 0 {
		return nil
	}

	c := make([]int, l)
	copy(c, s)
	return c
}

// CleanEnvVar replaces all occurrences of illegal characters in an environment
// variable with the specified byte.
func CleanEnvVar(s string, r byte) string {
	b := []byte(s)
	for i, c := range b {
		switch {
		case c == '_':
		case c == '.':
		case c >= 'a' && c <= 'z':
		case c >= 'A' && c <= 'Z':
		case i > 0 && c >= '0' && c <= '9':
		default:
			// Replace!
			b[i] = r
		}
	}
	return string(b)
}

// CleanFilename replaces invalid characters in filename
func CleanFilename(filename string, replace string) string {
	clean := invalidFilename.ReplaceAllLiteralString(filename, replace)
	return clean
}

// CleanFilenameASCIIOnly replaces invalid and non-ASCII characters in filename
func CleanFilenameASCIIOnly(filename string, replace string) string {
	clean := invalidFilenameNonASCII.ReplaceAllLiteralString(filename, replace)
	return clean
}

// CleanFilenameStrict replaces invalid and punctuation characters in filename
func CleanFilenameStrict(filename string, replace string) string {
	clean := invalidFilenameStrict.ReplaceAllLiteralString(filename, replace)
	return clean
}

func CheckHCLKeys(node ast.Node, valid []string) error {
	var list *ast.ObjectList
	switch n := node.(type) {
	case *ast.ObjectList:
		list = n
	case *ast.ObjectType:
		list = n.List
	default:
		return fmt.Errorf("cannot check HCL keys of type %T", n)
	}

	validMap := make(map[string]struct{}, len(valid))
	for _, v := range valid {
		validMap[v] = struct{}{}
	}

	var result error
	for _, item := range list.Items {
		key := item.Keys[0].Token.Value().(string)
		if _, ok := validMap[key]; !ok {
			result = multierror.Append(result, fmt.Errorf(
				"invalid key: %s", key))
		}
	}

	return result
}

// UnusedKeys returns a pretty-printed error if any `hcl:",unusedKeys"` is not empty
func UnusedKeys(obj interface{}) error {
	val := reflect.ValueOf(obj)
	if val.Kind() == reflect.Ptr {
		val = reflect.Indirect(val)
	}
	return unusedKeysImpl([]string{}, val)
}

func unusedKeysImpl(path []string, val reflect.Value) error {
	stype := val.Type()
	for i := 0; i < stype.NumField(); i++ {
		ftype := stype.Field(i)
		fval := val.Field(i)
		tags := strings.Split(ftype.Tag.Get("hcl"), ",")
		name := tags[0]
		tags = tags[1:]

		if fval.Kind() == reflect.Ptr {
			fval = reflect.Indirect(fval)
		}

		// struct? recurse. Add the struct's key to the path
		if fval.Kind() == reflect.Struct {
			err := unusedKeysImpl(append([]string{name}, path...), fval)
			if err != nil {
				return err
			}
			continue
		}

		// Search the hcl tags for "unusedKeys"
		unusedKeys := false
		for _, p := range tags {
			if p == "unusedKeys" {
				unusedKeys = true
				break
			}
		}

		if unusedKeys {
			ks, ok := fval.Interface().([]string)
			if ok && len(ks) != 0 {
				ps := ""
				if len(path) > 0 {
					ps = strings.Join(path, ".") + " "
				}
				return fmt.Errorf("%sunexpected keys %s",
					ps,
					strings.Join(ks, ", "))
			}
		}
	}
	return nil
}

// RemoveEqualFold removes the first string that EqualFold matches. It updates xs in place
func RemoveEqualFold(xs *[]string, search string) {
	sl := *xs
	for i, x := range sl {
		if strings.EqualFold(x, search) {
			sl = append(sl[:i], sl[i+1:]...)
			if len(sl) == 0 {
				*xs = nil
			} else {
				*xs = sl
			}
			return
		}
	}
}

// CheckNamespaceScope ensures that the provided namespace is equal to
// or a parent of the requested namespaces. Returns requested namespaces
// which are not equal to or a child of the provided namespace.
func CheckNamespaceScope(provided string, requested []string) []string {
	var offending []string
	for _, ns := range requested {
		rel, err := filepath.Rel(provided, ns)
		if err != nil {
			offending = append(offending, ns)
			// If relative path requires ".." it's not a child
		} else if strings.Contains(rel, "..") {
			offending = append(offending, ns)
		}
	}
	if len(offending) > 0 {
		return offending
	}
	return nil
}

// PathEscapesSandbox returns whether previously cleaned path inside the
// sandbox directory (typically this will be the allocation directory)
// escapes.
func PathEscapesSandbox(sandboxDir, path string) bool {
	rel, err := filepath.Rel(sandboxDir, path)
	if err != nil {
		return true
	}
	if strings.HasPrefix(rel, "..") {
		return true
	}
	return false
}

// StopFunc is used to stop a time.Timer created with NewSafeTimer
type StopFunc func()

// NewSafeTimer creates a time.Timer but does not panic if duration is <= 0.
//
// Using a time.Timer is recommended instead of time.After when it is necessary
// to avoid leaking goroutines (e.g. in a select inside a loop).
//
// Returns the time.Timer and also a StopFunc, forcing the caller to deal
// with stopping the time.Timer to avoid leaking a goroutine.
func NewSafeTimer(duration time.Duration) (*time.Timer, StopFunc) {
	if duration <= 0 {
		// Avoid panic by using the smallest positive value. This is close enough
		// to the behavior of time.After(0), which this helper is intended to
		// replace.
		// https://go.dev/play/p/EIkm9MsPbHY
		duration = 1
	}

	t := time.NewTimer(duration)
	cancel := func() {
		t.Stop()
	}

	return t, cancel
}