source: code/trunk/vendor/golang.org/x/net/idna/idna9.0.0.go@ 145

// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.

// Copyright 2016 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.

//go:build !go1.10
// +build !go1.10

// Package idna implements IDNA2008 using the compatibility processing
// defined by UTS (Unicode Technical Standard) #46, which defines a standard to
// deal with the transition from IDNA2003.
//
// IDNA2008 (Internationalized Domain Names for Applications), is defined in RFC
// 5890, RFC 5891, RFC 5892, RFC 5893 and RFC 5894.
// UTS #46 is defined in https://www.unicode.org/reports/tr46.
// See https://unicode.org/cldr/utility/idna.jsp for a visualization of the
// differences between these two standards.
package idna // import "golang.org/x/net/idna"

import (
        "fmt"
        "strings"
        "unicode/utf8"

        "golang.org/x/text/secure/bidirule"
        "golang.org/x/text/unicode/norm"
)

// NOTE: Unlike common practice in Go APIs, the functions will return a
// sanitized domain name in case of errors. Browsers sometimes use a partially
// evaluated string as lookup.
// TODO: the current error handling is, in my opinion, the least opinionated.
// Other strategies are also viable, though:
// Option 1) Return an empty string in case of error, but allow the user to
//    specify explicitly which errors to ignore.
// Option 2) Return the partially evaluated string if it is itself a valid
//    string, otherwise return the empty string in case of error.
// Option 3) Option 1 and 2.
// Option 4) Always return an empty string for now and implement Option 1 as
//    needed, and document that the return string may not be empty in case of
//    error in the future.
// I think Option 1 is best, but it is quite opinionated.

// ToASCII is a wrapper for Punycode.ToASCII.
func ToASCII(s string) (string, error) {
        return Punycode.process(s, true)
}

// ToUnicode is a wrapper for Punycode.ToUnicode.
func ToUnicode(s string) (string, error) {
        return Punycode.process(s, false)
}

// An Option configures a Profile at creation time.
type Option func(*options)

// Transitional sets a Profile to use the Transitional mapping as defined in UTS
// #46. This will cause, for example, "ß" to be mapped to "ss". Using the
// transitional mapping provides a compromise between IDNA2003 and IDNA2008
// compatibility. It is used by some browsers when resolving domain names. This
// option is only meaningful if combined with MapForLookup.
func Transitional(transitional bool) Option {
        return func(o *options) { o.transitional = transitional }
}

// VerifyDNSLength sets whether a Profile should fail if any of the IDN parts
// are longer than allowed by the RFC.
//
// This option corresponds to the VerifyDnsLength flag in UTS #46.
func VerifyDNSLength(verify bool) Option {
        return func(o *options) { o.verifyDNSLength = verify }
}

// RemoveLeadingDots removes leading label separators. Leading runes that map to
// dots, such as U+3002 IDEOGRAPHIC FULL STOP, are removed as well.
func RemoveLeadingDots(remove bool) Option {
        return func(o *options) { o.removeLeadingDots = remove }
}

// ValidateLabels sets whether to check the mandatory label validation criteria
// as defined in Section 5.4 of RFC 5891. This includes testing for correct use
// of hyphens ('-'), normalization, validity of runes, and the context rules.
// In particular, ValidateLabels also sets the CheckHyphens and CheckJoiners flags
// in UTS #46.
func ValidateLabels(enable bool) Option {
        return func(o *options) {
                // Don't override existing mappings, but set one that at least checks
                // normalization if it is not set.
                if o.mapping == nil && enable {
                        o.mapping = normalize
                }
                o.trie = trie
                o.checkJoiners = enable
                o.checkHyphens = enable
                if enable {
                        o.fromPuny = validateFromPunycode
                } else {
                        o.fromPuny = nil
                }
        }
}

// CheckHyphens sets whether to check for correct use of hyphens ('-') in
// labels. Most web browsers do not have this option set, since labels such as
// "r3---sn-apo3qvuoxuxbt-j5pe" are in common use.
//
// This option corresponds to the CheckHyphens flag in UTS #46.
func CheckHyphens(enable bool) Option {
        return func(o *options) { o.checkHyphens = enable }
}

// CheckJoiners sets whether to check the ContextJ rules as defined in Appendix
// A of RFC 5892, concerning the use of joiner runes.
//
// This option corresponds to the CheckJoiners flag in UTS #46.
func CheckJoiners(enable bool) Option {
        return func(o *options) {
                o.trie = trie
                o.checkJoiners = enable
        }
}

// StrictDomainName limits the set of permissable ASCII characters to those
// allowed in domain names as defined in RFC 1034 (A-Z, a-z, 0-9 and the
// hyphen). This is set by default for MapForLookup and ValidateForRegistration,
// but is only useful if ValidateLabels is set.
//
// This option is useful, for instance, for browsers that allow characters
// outside this range, for example a '_' (U+005F LOW LINE). See
// http://www.rfc-editor.org/std/std3.txt for more details.
//
// This option corresponds to the UseSTD3ASCIIRules flag in UTS #46.
func StrictDomainName(use bool) Option {
        return func(o *options) { o.useSTD3Rules = use }
}

// NOTE: the following options pull in tables. The tables should not be linked
// in as long as the options are not used.

// BidiRule enables the Bidi rule as defined in RFC 5893. Any application
// that relies on proper validation of labels should include this rule.
//
// This option corresponds to the CheckBidi flag in UTS #46.
func BidiRule() Option {
        return func(o *options) { o.bidirule = bidirule.ValidString }
}

// ValidateForRegistration sets validation options to verify that a given IDN is
// properly formatted for registration as defined by Section 4 of RFC 5891.
func ValidateForRegistration() Option {
        return func(o *options) {
                o.mapping = validateRegistration
                StrictDomainName(true)(o)
                ValidateLabels(true)(o)
                VerifyDNSLength(true)(o)
                BidiRule()(o)
        }
}

// MapForLookup sets validation and mapping options such that a given IDN is
// transformed for domain name lookup according to the requirements set out in
// Section 5 of RFC 5891. The mappings follow the recommendations of RFC 5894,
// RFC 5895 and UTS 46. It does not add the Bidi Rule. Use the BidiRule option
// to add this check.
//
// The mappings include normalization and mapping case, width and other
// compatibility mappings.
func MapForLookup() Option {
        return func(o *options) {
                o.mapping = validateAndMap
                StrictDomainName(true)(o)
                ValidateLabels(true)(o)
                RemoveLeadingDots(true)(o)
        }
}

type options struct {
        transitional      bool
        useSTD3Rules      bool
        checkHyphens      bool
        checkJoiners      bool
        verifyDNSLength   bool
        removeLeadingDots bool

        trie *idnaTrie

        // fromPuny calls validation rules when converting A-labels to U-labels.
        fromPuny func(p *Profile, s string) error

        // mapping implements a validation and mapping step as defined in RFC 5895
        // or UTS 46, tailored to, for example, domain registration or lookup.
        mapping func(p *Profile, s string) (string, error)

        // bidirule, if specified, checks whether s conforms to the Bidi Rule
        // defined in RFC 5893.
        bidirule func(s string) bool
}

// A Profile defines the configuration of a IDNA mapper.
type Profile struct {
        options
}

func apply(o *options, opts []Option) {
        for _, f := range opts {
                f(o)
        }
}

// New creates a new Profile.
//
// With no options, the returned Profile is the most permissive and equals the
// Punycode Profile. Options can be passed to further restrict the Profile. The
// MapForLookup and ValidateForRegistration options set a collection of options,
// for lookup and registration purposes respectively, which can be tailored by
// adding more fine-grained options, where later options override earlier
// options.
func New(o ...Option) *Profile {
        p := &Profile{}
        apply(&p.options, o)
        return p
}

// ToASCII converts a domain or domain label to its ASCII form. For example,
// ToASCII("bücher.example.com") is "xn--bcher-kva.example.com", and
// ToASCII("golang") is "golang". If an error is encountered it will return
// an error and a (partially) processed result.
func (p *Profile) ToASCII(s string) (string, error) {
        return p.process(s, true)
}

// ToUnicode converts a domain or domain label to its Unicode form. For example,
// ToUnicode("xn--bcher-kva.example.com") is "bücher.example.com", and
// ToUnicode("golang") is "golang". If an error is encountered it will return
// an error and a (partially) processed result.
func (p *Profile) ToUnicode(s string) (string, error) {
        pp := *p
        pp.transitional = false
        return pp.process(s, false)
}

// String reports a string with a description of the profile for debugging
// purposes. The string format may change with different versions.
func (p *Profile) String() string {
        s := ""
        if p.transitional {
                s = "Transitional"
        } else {
                s = "NonTransitional"
        }
        if p.useSTD3Rules {
                s += ":UseSTD3Rules"
        }
        if p.checkHyphens {
                s += ":CheckHyphens"
        }
        if p.checkJoiners {
                s += ":CheckJoiners"
        }
        if p.verifyDNSLength {
                s += ":VerifyDNSLength"
        }
        return s
}

var (
        // Punycode is a Profile that does raw punycode processing with a minimum
        // of validation.
        Punycode *Profile = punycode

        // Lookup is the recommended profile for looking up domain names, according
        // to Section 5 of RFC 5891. The exact configuration of this profile may
        // change over time.
        Lookup *Profile = lookup

        // Display is the recommended profile for displaying domain names.
        // The configuration of this profile may change over time.
        Display *Profile = display

        // Registration is the recommended profile for checking whether a given
        // IDN is valid for registration, according to Section 4 of RFC 5891.
        Registration *Profile = registration

        punycode = &Profile{}
        lookup   = &Profile{options{
                transitional:      true,
                removeLeadingDots: true,
                useSTD3Rules:      true,
                checkHyphens:      true,
                checkJoiners:      true,
                trie:              trie,
                fromPuny:          validateFromPunycode,
                mapping:           validateAndMap,
                bidirule:          bidirule.ValidString,
        }}
        display = &Profile{options{
                useSTD3Rules:      true,
                removeLeadingDots: true,
                checkHyphens:      true,
                checkJoiners:      true,
                trie:              trie,
                fromPuny:          validateFromPunycode,
                mapping:           validateAndMap,
                bidirule:          bidirule.ValidString,
        }}
        registration = &Profile{options{
                useSTD3Rules:    true,
                verifyDNSLength: true,
                checkHyphens:    true,
                checkJoiners:    true,
                trie:            trie,
                fromPuny:        validateFromPunycode,
                mapping:         validateRegistration,
                bidirule:        bidirule.ValidString,
        }}

        // TODO: profiles
        // Register: recommended for approving domain names: don't do any mappings
        // but rather reject on invalid input. Bundle or block deviation characters.
)

type labelError struct{ label, code_ string }

func (e labelError) code() string { return e.code_ }
func (e labelError) Error() string {
        return fmt.Sprintf("idna: invalid label %q", e.label)
}

type runeError rune

func (e runeError) code() string { return "P1" }
func (e runeError) Error() string {
        return fmt.Sprintf("idna: disallowed rune %U", e)
}

// process implements the algorithm described in section 4 of UTS #46,
// see https://www.unicode.org/reports/tr46.
func (p *Profile) process(s string, toASCII bool) (string, error) {
        var err error
        if p.mapping != nil {
                s, err = p.mapping(p, s)
        }
        // Remove leading empty labels.
        if p.removeLeadingDots {
                for ; len(s) > 0 && s[0] == '.'; s = s[1:] {
                }
        }
        // It seems like we should only create this error on ToASCII, but the
        // UTS 46 conformance tests suggests we should always check this.
        if err == nil && p.verifyDNSLength && s == "" {
                err = &labelError{s, "A4"}
        }
        labels := labelIter{orig: s}
        for ; !labels.done(); labels.next() {
                label := labels.label()
                if label == "" {
                        // Empty labels are not okay. The label iterator skips the last
                        // label if it is empty.
                        if err == nil && p.verifyDNSLength {
                                err = &labelError{s, "A4"}
                        }
                        continue
                }
                if strings.HasPrefix(label, acePrefix) {
                        u, err2 := decode(label[len(acePrefix):])
                        if err2 != nil {
                                if err == nil {
                                        err = err2
                                }
                                // Spec says keep the old label.
                                continue
                        }
                        labels.set(u)
                        if err == nil && p.fromPuny != nil {
                                err = p.fromPuny(p, u)
                        }
                        if err == nil {
                                // This should be called on NonTransitional, according to the
                                // spec, but that currently does not have any effect. Use the
                                // original profile to preserve options.
                                err = p.validateLabel(u)
                        }
                } else if err == nil {
                        err = p.validateLabel(label)
                }
        }
        if toASCII {
                for labels.reset(); !labels.done(); labels.next() {
                        label := labels.label()
                        if !ascii(label) {
                                a, err2 := encode(acePrefix, label)
                                if err == nil {
                                        err = err2
                                }
                                label = a
                                labels.set(a)
                        }
                        n := len(label)
                        if p.verifyDNSLength && err == nil && (n == 0 || n > 63) {
                                err = &labelError{label, "A4"}
                        }
                }
        }
        s = labels.result()
        if toASCII && p.verifyDNSLength && err == nil {
                // Compute the length of the domain name minus the root label and its dot.
                n := len(s)
                if n > 0 && s[n-1] == '.' {
                        n--
                }
                if len(s) < 1 || n > 253 {
                        err = &labelError{s, "A4"}
                }
        }
        return s, err
}

func normalize(p *Profile, s string) (string, error) {
        return norm.NFC.String(s), nil
}

func validateRegistration(p *Profile, s string) (string, error) {
        if !norm.NFC.IsNormalString(s) {
                return s, &labelError{s, "V1"}
        }
        for i := 0; i < len(s); {
                v, sz := trie.lookupString(s[i:])
                // Copy bytes not copied so far.
                switch p.simplify(info(v).category()) {
                // TODO: handle the NV8 defined in the Unicode idna data set to allow
                // for strict conformance to IDNA2008.
                case valid, deviation:
                case disallowed, mapped, unknown, ignored:
                        r, _ := utf8.DecodeRuneInString(s[i:])
                        return s, runeError(r)
                }
                i += sz
        }
        return s, nil
}

func validateAndMap(p *Profile, s string) (string, error) {
        var (
                err error
                b   []byte
                k   int
        )
        for i := 0; i < len(s); {
                v, sz := trie.lookupString(s[i:])
                start := i
                i += sz
                // Copy bytes not copied so far.
                switch p.simplify(info(v).category()) {
                case valid:
                        continue
                case disallowed:
                        if err == nil {
                                r, _ := utf8.DecodeRuneInString(s[start:])
                                err = runeError(r)
                        }
                        continue
                case mapped, deviation:
                        b = append(b, s[k:start]...)
                        b = info(v).appendMapping(b, s[start:i])
                case ignored:
                        b = append(b, s[k:start]...)
                        // drop the rune
                case unknown:
                        b = append(b, s[k:start]...)
                        b = append(b, "\ufffd"...)
                }
                k = i
        }
        if k == 0 {
                // No changes so far.
                s = norm.NFC.String(s)
        } else {
                b = append(b, s[k:]...)
                if norm.NFC.QuickSpan(b) != len(b) {
                        b = norm.NFC.Bytes(b)
                }
                // TODO: the punycode converters require strings as input.
                s = string(b)
        }
        return s, err
}

// A labelIter allows iterating over domain name labels.
type labelIter struct {
        orig     string
        slice    []string
        curStart int
        curEnd   int
        i        int
}

func (l *labelIter) reset() {
        l.curStart = 0
        l.curEnd = 0
        l.i = 0
}

func (l *labelIter) done() bool {
        return l.curStart >= len(l.orig)
}

func (l *labelIter) result() string {
        if l.slice != nil {
                return strings.Join(l.slice, ".")
        }
        return l.orig
}

func (l *labelIter) label() string {
        if l.slice != nil {
                return l.slice[l.i]
        }
        p := strings.IndexByte(l.orig[l.curStart:], '.')
        l.curEnd = l.curStart + p
        if p == -1 {
                l.curEnd = len(l.orig)
        }
        return l.orig[l.curStart:l.curEnd]
}

// next sets the value to the next label. It skips the last label if it is empty.
func (l *labelIter) next() {
        l.i++
        if l.slice != nil {
                if l.i >= len(l.slice) || l.i == len(l.slice)-1 && l.slice[l.i] == "" {
                        l.curStart = len(l.orig)
                }
        } else {
                l.curStart = l.curEnd + 1
                if l.curStart == len(l.orig)-1 && l.orig[l.curStart] == '.' {
                        l.curStart = len(l.orig)
                }
        }
}

func (l *labelIter) set(s string) {
        if l.slice == nil {
                l.slice = strings.Split(l.orig, ".")
        }
        l.slice[l.i] = s
}

// acePrefix is the ASCII Compatible Encoding prefix.
const acePrefix = "xn--"

func (p *Profile) simplify(cat category) category {
        switch cat {
        case disallowedSTD3Mapped:
                if p.useSTD3Rules {
                        cat = disallowed
                } else {
                        cat = mapped
                }
        case disallowedSTD3Valid:
                if p.useSTD3Rules {
                        cat = disallowed
                } else {
                        cat = valid
                }
        case deviation:
                if !p.transitional {
                        cat = valid
                }
        case validNV8, validXV8:
                // TODO: handle V2008
                cat = valid
        }
        return cat
}

func validateFromPunycode(p *Profile, s string) error {
        if !norm.NFC.IsNormalString(s) {
                return &labelError{s, "V1"}
        }
        for i := 0; i < len(s); {
                v, sz := trie.lookupString(s[i:])
                if c := p.simplify(info(v).category()); c != valid && c != deviation {
                        return &labelError{s, "V6"}
                }
                i += sz
        }
        return nil
}

const (
        zwnj = "\u200c"
        zwj  = "\u200d"
)

type joinState int8

const (
        stateStart joinState = iota
        stateVirama
        stateBefore
        stateBeforeVirama
        stateAfter
        stateFAIL
)

var joinStates = [][numJoinTypes]joinState{
        stateStart: {
                joiningL:   stateBefore,
                joiningD:   stateBefore,
                joinZWNJ:   stateFAIL,
                joinZWJ:    stateFAIL,
                joinVirama: stateVirama,
        },
        stateVirama: {
                joiningL: stateBefore,
                joiningD: stateBefore,
        },
        stateBefore: {
                joiningL:   stateBefore,
                joiningD:   stateBefore,
                joiningT:   stateBefore,
                joinZWNJ:   stateAfter,
                joinZWJ:    stateFAIL,
                joinVirama: stateBeforeVirama,
        },
        stateBeforeVirama: {
                joiningL: stateBefore,
                joiningD: stateBefore,
                joiningT: stateBefore,
        },
        stateAfter: {
                joiningL:   stateFAIL,
                joiningD:   stateBefore,
                joiningT:   stateAfter,
                joiningR:   stateStart,
                joinZWNJ:   stateFAIL,
                joinZWJ:    stateFAIL,
                joinVirama: stateAfter, // no-op as we can't accept joiners here
        },
        stateFAIL: {
                0:          stateFAIL,
                joiningL:   stateFAIL,
                joiningD:   stateFAIL,
                joiningT:   stateFAIL,
                joiningR:   stateFAIL,
                joinZWNJ:   stateFAIL,
                joinZWJ:    stateFAIL,
                joinVirama: stateFAIL,
        },
}

// validateLabel validates the criteria from Section 4.1. Item 1, 4, and 6 are
// already implicitly satisfied by the overall implementation.
func (p *Profile) validateLabel(s string) error {
        if s == "" {
                if p.verifyDNSLength {
                        return &labelError{s, "A4"}
                }
                return nil
        }
        if p.bidirule != nil && !p.bidirule(s) {
                return &labelError{s, "B"}
        }
        if p.checkHyphens {
                if len(s) > 4 && s[2] == '-' && s[3] == '-' {
                        return &labelError{s, "V2"}
                }
                if s[0] == '-' || s[len(s)-1] == '-' {
                        return &labelError{s, "V3"}
                }
        }
        if !p.checkJoiners {
                return nil
        }
        trie := p.trie // p.checkJoiners is only set if trie is set.
        // TODO: merge the use of this in the trie.
        v, sz := trie.lookupString(s)
        x := info(v)
        if x.isModifier() {
                return &labelError{s, "V5"}
        }
        // Quickly return in the absence of zero-width (non) joiners.
        if strings.Index(s, zwj) == -1 && strings.Index(s, zwnj) == -1 {
                return nil
        }
        st := stateStart
        for i := 0; ; {
                jt := x.joinType()
                if s[i:i+sz] == zwj {
                        jt = joinZWJ
                } else if s[i:i+sz] == zwnj {
                        jt = joinZWNJ
                }
                st = joinStates[st][jt]
                if x.isViramaModifier() {
                        st = joinStates[st][joinVirama]
                }
                if i += sz; i == len(s) {
                        break
                }
                v, sz = trie.lookupString(s[i:])
                x = info(v)
        }
        if st == stateFAIL || st == stateAfter {
                return &labelError{s, "C"}
        }
        return nil
}

func ascii(s string) bool {
        for i := 0; i < len(s); i++ {
                if s[i] >= utf8.RuneSelf {
                        return false
                }
        }
        return true
}