/*
 * 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`

    `github.com/bytedance/sonic/internal/rt`
    `github.com/bytedance/sonic/option`
)

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

const (
    bitSortMapKeys = iota
)

const (
    // SortMapKeys indicate 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 << bitSortMapKeys
)

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

// Encode returns the JSON encoding of v.
func (self *Encoder) Encode(v interface{}) ([]byte, error) {
    return Encode(v, self.Opts)
}

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

// Quote returns the JSON-quoted version of s.
func Quote(s string) string {
    var n int
    var p []byte

    /* check for empty string */
    if s == "" {
        return `""`
    }

    /* allocate space for result */
    n = len(s) + 2
    p = make([]byte, 0, n)

    /* call the encoder */
    _ = encodeString(&p, s)
    return rt.Mem2Str(p)
}

// Encode returns the JSON encoding of val, encoded with opts.
func Encode(val interface{}, opts Options) ([]byte, error) {
    buf := newBytes()
    err := EncodeInto(&buf, val, opts)

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

    /* make a copy of the result */
    ret := make([]byte, len(buf))
    copy(ret, buf)

    /* return the buffer into pool */
    freeBytes(buf)
    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 {
    stk := newStack()
    efv := rt.UnpackEface(val)
    err := encodeTypedPointer(buf, efv.Type, &efv.Value, stk, uint64(opts))

    /* return the stack into pool */
    if err != nil {
        resetStack(stk)
    }
    freeStack(stk)

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

// 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 out []byte
    var buf *bytes.Buffer

    /* encode into the buffer */
    out = newBytes()
    err = EncodeInto(&out, val, opts)

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

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

    /* check for errors */
    if err != nil {
        freeBytes(out)
        freeBuffer(buf)
        return nil, err
    }

    /* copy to the result buffer */
    ret := make([]byte, buf.Len())
    copy(ret, buf.Bytes())

    /* return the buffers into pool */
    freeBytes(out)
    freeBuffer(buf)
    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)
        break
    }
    return pretouchRec(map[reflect.Type]bool{vt:true}, cfg)
}

func pretouchType(_vt reflect.Type, opts option.CompileOptions) (map[reflect.Type]bool, error) {
    /* compile function */
    compiler := newCompiler().apply(opts)
    encoder := func(vt *rt.GoType) (interface{}, error) {
        if pp, err := compiler.compile(_vt); err != nil {
            return nil, err
        } else {
            return newAssembler(pp).Load(), nil
        }
    }

    /* find or compile */
    vt := rt.UnpackType(_vt)
    if val := programCache.Get(vt); val != nil {
        return nil, nil
    } else if _, err := programCache.Compute(vt, encoder); err == nil {
        return compiler.rec, nil
    } else {
        return nil, err
    }
}

func pretouchRec(vtm map[reflect.Type]bool, opts option.CompileOptions) error {
    if opts.RecursiveDepth < 0 || len(vtm) == 0 {
        return nil
    }
    next := make(map[reflect.Type]bool)
    for vt, _ := range(vtm) {
        sub, err := pretouchType(vt, opts)
        if err != nil {
            return err
        }
        for svt, _ := range(sub) {
            next[svt] = true
        }
    }
    opts.RecursiveDepth -= 1
    return pretouchRec(next, opts)
}