/*
 * Copyright 2021 ByteDance 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 encoder

import (
	"bytes"
	"encoding/json"
	"reflect"
	"runtime"
	"unsafe"

	"github.com/bytedance/sonic/utf8"
	"github.com/bytedance/sonic/internal/encoder/alg"
	"github.com/bytedance/sonic/internal/encoder/vars"
	"github.com/bytedance/sonic/internal/rt"
	"github.com/bytedance/sonic/option"
)

// Options is a set of encoding options.
type Options uint64

const (
    // SortMapKeys indicates that the keys of a map needs to be sorted 
    // before serializing into JSON.
    // WARNING: This hurts performance A LOT, USE WITH CARE.
    SortMapKeys          Options = 1 << alg.BitSortMapKeys

    // EscapeHTML indicates encoder to escape all HTML characters 
    // after serializing into JSON (see https://pkg.go.dev/encoding/json#HTMLEscape).
    // WARNING: This hurts performance A LOT, USE WITH CARE.
    EscapeHTML           Options = 1 << alg.BitEscapeHTML

    // CompactMarshaler indicates that the output JSON from json.Marshaler 
    // is always compact and needs no validation 
    CompactMarshaler     Options = 1 << alg.BitCompactMarshaler

    // NoQuoteTextMarshaler indicates that the output text from encoding.TextMarshaler 
    // is always escaped string and needs no quoting
    NoQuoteTextMarshaler Options = 1 << alg.BitNoQuoteTextMarshaler

    // NoNullSliceOrMap indicates all empty Array or Object are encoded as '[]' or '{}',
    // instead of 'null'. 
    // NOTE: The priority of this option is lower than json tag `omitempty`.
    NoNullSliceOrMap     Options = 1 << alg.BitNoNullSliceOrMap

    // ValidateString indicates that encoder should validate the input string
    // before encoding it into JSON.
    ValidateString       Options = 1 << alg.BitValidateString

    // NoValidateJSONMarshaler indicates that the encoder should not validate the output string
    // after encoding the JSONMarshaler to JSON.
    NoValidateJSONMarshaler Options = 1 << alg.BitNoValidateJSONMarshaler

    // NoEncoderNewline indicates that the encoder should not add a newline after every message
    NoEncoderNewline Options = 1 << alg.BitNoEncoderNewline
  
    // CompatibleWithStd is used to be compatible with std encoder.
    CompatibleWithStd Options = SortMapKeys | EscapeHTML | CompactMarshaler

    // Encode Infinity or Nan float into `null`, instead of returning an error.
    EncodeNullForInfOrNan Options = 1 << alg.BitEncodeNullForInfOrNan
)

// Encoder represents a specific set of encoder configurations.
type Encoder struct {
    Opts Options
    prefix string
    indent string
}

// Encode returns the JSON encoding of v.
func (self *Encoder) Encode(v interface{}) ([]byte, error) {
    if self.indent != "" || self.prefix != "" { 
        return EncodeIndented(v, self.prefix, self.indent, self.Opts)
    }
    return Encode(v, self.Opts)
}

// SortKeys enables the SortMapKeys option.
func (self *Encoder) SortKeys() *Encoder {
    self.Opts |= SortMapKeys
    return self
}

// SetEscapeHTML specifies if option EscapeHTML opens
func (self *Encoder) SetEscapeHTML(f bool) {
    if f {
        self.Opts |= EscapeHTML
    } else {
        self.Opts &= ^EscapeHTML
    }
}

// SetValidateString specifies if option ValidateString opens
func (self *Encoder) SetValidateString(f bool) {
    if f {
        self.Opts |= ValidateString
    } else {
        self.Opts &= ^ValidateString
    }
}

// SetNoValidateJSONMarshaler specifies if option NoValidateJSONMarshaler opens
func (self *Encoder) SetNoValidateJSONMarshaler(f bool) {
    if f {
        self.Opts |= NoValidateJSONMarshaler
    } else {
        self.Opts &= ^NoValidateJSONMarshaler
    }
}

// SetNoEncoderNewline specifies if option NoEncoderNewline opens
func (self *Encoder) SetNoEncoderNewline(f bool) {
    if f {
        self.Opts |= NoEncoderNewline
    } else {
        self.Opts &= ^NoEncoderNewline
    }
}


// SetCompactMarshaler specifies if option CompactMarshaler opens
func (self *Encoder) SetCompactMarshaler(f bool) {
    if f {
        self.Opts |= CompactMarshaler
    } else {
        self.Opts &= ^CompactMarshaler
    }
}

// SetNoQuoteTextMarshaler specifies if option NoQuoteTextMarshaler opens
func (self *Encoder) SetNoQuoteTextMarshaler(f bool) {
    if f {
        self.Opts |= NoQuoteTextMarshaler
    } else {
        self.Opts &= ^NoQuoteTextMarshaler
    }
}

// SetIndent instructs the encoder to format each subsequent encoded
// value as if indented by the package-level function EncodeIndent().
// Calling SetIndent("", "") disables indentation.
func (enc *Encoder) SetIndent(prefix, indent string) {
    enc.prefix = prefix
    enc.indent = indent
}

// Quote returns the JSON-quoted version of s.
func Quote(s string) string {
    buf := make([]byte, 0, len(s)+2)
    buf = alg.Quote(buf, s, false)
    return rt.Mem2Str(buf)
}

// Encode returns the JSON encoding of val, encoded with opts.
func Encode(val interface{}, opts Options) ([]byte, error) {
    var ret []byte

    buf := vars.NewBytes()
    err := encodeIntoCheckRace(buf, val, opts)

    /* check for errors */
    if err != nil {
        vars.FreeBytes(buf)
        return nil, err
    }

    /* htmlescape or correct UTF-8 if opts enable */
    old := buf
    *buf = encodeFinish(*old, opts)
    pbuf := ((*rt.GoSlice)(unsafe.Pointer(buf))).Ptr
    pold := ((*rt.GoSlice)(unsafe.Pointer(old))).Ptr

    /* return when allocated a new buffer */
    if pbuf != pold {
        vars.FreeBytes(old)
        return *buf, nil
    }

    /* make a copy of the result */
    if rt.CanSizeResue(cap(*buf)) {
        ret = make([]byte, len(*buf))
        copy(ret, *buf)
        vars.FreeBytes(buf)
    } else {
        ret = *buf
    }
    
    /* return the buffer into pool */
    return ret, nil
}

// EncodeInto is like Encode but uses a user-supplied buffer instead of allocating
// a new one.
func EncodeInto(buf *[]byte, val interface{}, opts Options) error {
    err := encodeIntoCheckRace(buf, val, opts)
    if err != nil {
        return err
    }
    *buf = encodeFinish(*buf, opts)
    return err
}

func encodeInto(buf *[]byte, val interface{}, opts Options) error {
    stk := vars.NewStack()
    efv := rt.UnpackEface(val)
    err := encodeTypedPointer(buf, efv.Type, &efv.Value, stk, uint64(opts))

    /* return the stack into pool */
    if err != nil {
        vars.ResetStack(stk)
    }
    vars.FreeStack(stk)

    /* avoid GC ahead */
    runtime.KeepAlive(buf)
    runtime.KeepAlive(efv)
    return err
}

func encodeFinish(buf []byte, opts Options) []byte {
    if opts & EscapeHTML != 0 {
        buf = HTMLEscape(nil, buf)
    }
    if (opts & ValidateString != 0) && !utf8.Validate(buf) {
        buf = utf8.CorrectWith(nil, buf, `\ufffd`)
    }
    return buf
}


// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
// so that the JSON will be safe to embed inside HTML <script> tags.
// For historical reasons, web browsers don't honor standard HTML
// escaping within <script> tags, so an alternative JSON encoding must
// be used.
func HTMLEscape(dst []byte, src []byte) []byte {
    return alg.HtmlEscape(dst, src)
}

// EncodeIndented is like Encode but applies Indent to format the output.
// Each JSON element in the output will begin on a new line beginning with prefix
// followed by one or more copies of indent according to the indentation nesting.
func EncodeIndented(val interface{}, prefix string, indent string, opts Options) ([]byte, error) {
    var err error
    var buf *bytes.Buffer

    /* encode into the buffer */
    out := vars.NewBytes()
    err = EncodeInto(out, val, opts)

    /* check for errors */
    if err != nil {
        vars.FreeBytes(out)
        return nil, err
    }

    /* indent the JSON */
    buf = vars.NewBuffer()
    err = json.Indent(buf, *out, prefix, indent)
    vars.FreeBytes(out)

    /* check for errors */
    if err != nil {
        vars.FreeBuffer(buf)
        return nil, err
    }

    /* copy to the result buffer */
    var ret []byte
    if rt.CanSizeResue(cap(buf.Bytes())) {
        ret = make([]byte, buf.Len())
        copy(ret, buf.Bytes())
        /* return the buffers into pool */
        vars.FreeBuffer(buf)
    } else {
        ret = buf.Bytes()
    }
    
    return ret, nil
}

// Pretouch compiles vt ahead-of-time to avoid JIT compilation on-the-fly, in
// order to reduce the first-hit latency.
//
// Opts are the compile options, for example, "option.WithCompileRecursiveDepth" is
// a compile option to set the depth of recursive compile for the nested struct type.
func Pretouch(vt reflect.Type, opts ...option.CompileOption) error {
    cfg := option.DefaultCompileOptions()
    for _, opt := range opts {
        opt(&cfg)
    }
    return pretouchRec(map[reflect.Type]uint8{vt: 0}, cfg)
}

// Valid validates json and returns first non-blank character position,
// if it is only one valid json value.
// Otherwise returns invalid character position using start.
//
// Note: it does not check for the invalid UTF-8 characters.
func Valid(data []byte) (ok bool, start int) {
    return alg.Valid(data)
}
