# qs #
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Zero-dependencies package to encodes structs into url.Values.

## Installation
```bash
go get github.com/sonh/qs
```

## Usage
```go
import (
    "github.com/sonh/qs"
)
```
Package qs exports `NewEncoder()` function to create an encoder. 

Encoder caches struct info to speed up encoding process, use a single instance is highly recommended. 

Use `WithTagAlias()` func to register custom tag alias (default is `qs`)
```go
encoder = qs.NewEncoder(
    qs.WithTagAlias("myTag"),
)
```

Encoder has `Values()` and `Encode()` functions to encode structs into `url.Values`.

### Supported data types:
- all basic types (`bool`, `uint`, `string`, `float64`,...)
- `struct`
- `slice`, `array`
- `pointer`
- `time.Time`   
- custom type

### Example
```go
type Query struct {
    Tags   []string  `qs:"tags"`
    Limit  int       `qs:"limit"`
    From   time.Time `qs:"from"`
    Active bool      `qs:"active,omitempty"`  //omit empty value
    Ignore float64   `qs:"-"`                 //ignore
}

query := &Query{
    Tags:   []string{"docker", "golang", "reactjs"},
    Limit:  24,
    From:   time.Unix(1580601600, 0).UTC(),
    Ignore: 0,
}

encoder := qs.NewEncoder()
values, err := encoder.Values(query)
if err != nil {
    // Handle error
}
fmt.Println(values.Encode()) //(unescaped) output: "from=2020-02-02T00:00:00Z&limit=24&tags=docker&tags=golang&tags=reactjs"
```
### Bool format
Use `int` option to encode bool to integer
```go
type Query struct {
    DefaultFmt bool `qs:"default_fmt"`
    IntFmt     bool `qs:"int_fmt,int"`
}

query := &Query{
    DefaultFmt: true, 
    IntFmt:     true,
}
values, _ := encoder.Values(query)
fmt.Println(values.Encode()) // (unescaped) output: "default_fmt=true&int_fmt=1"
```
### Time format
By default, package encodes time.Time values as RFC3339 format. 

Including the `"second"` or `"millis"` option to signal that the field should be encoded as second or millisecond.
```go
type Query struct {
    Default time.Time   `qs:"default_fmt"`
    Second  time.Time   `qs:"second_fmt,second"` //use `second` option
    Millis  time.Time   `qs:"millis_fmt,millis"` //use `millis` option
}

t := time.Unix(1580601600, 0).UTC()
query := &Query{
    Default: t,
    Second:  t,
    Millis:  t,
}

encoder := qs.NewEncoder()
values, _ := encoder.Values(query)
fmt.Println(values.Encode()) // (unescaped) output: "default_fmt=2020-02-02T00:00:00Z&millis_fmt=1580601600000&second_fmt=1580601600"
```

### Slice/Array Format
Slice and Array default to encoding into multiple URL values of the same value name.
```go
type Query struct {
    Tags []string `qs:"tags"`
}

values, _ := encoder.Values(&Query{Tags: []string{"foo","bar"}})
fmt.Println(values.Encode()) //(unescaped) output: "tags=foo&tags=bar"
```

Including the `comma` option to signal that the field should be encoded as a single comma-delimited value.
```go
type Query struct {
    Tags []string `qs:"tags,comma"`
}

values, _ := encoder.Values(&Query{Tags: []string{"foo","bar"}})
fmt.Println(values.Encode()) //(unescaped) output: "tags=foo,bar"
```

Including the `bracket` option to signal that the multiple URL values should have "[]" appended to the value name.
```go
type Query struct {
    Tags []string `qs:"tags,bracket"`
}

values, _ := encoder.Values(&Query{Tags: []string{"foo","bar"}})
fmt.Println(values.Encode()) //(unescaped) output: "tags[]=foo&tags[]=bar"
```

The `index` option will append an index number with brackets to value name.
```go
type Query struct {
    Tags []string `qs:"tags,index"`
}

values, _ := encoder.Values(&Query{Tags: []string{"foo","bar"}})
fmt.Println(values.Encode()) //(unescaped) output: "tags[0]=foo&tags[1]=bar"
```

### Nested structs
All nested structs are encoded including the parent value name with brackets for scoping.
```go
type User struct {
    Verified bool      `qs:"verified"`
    From     time.Time `qs:"from,millis"`
}

type Query struct {
    User User `qs:"user"`
}

query := Query{
    User: User{
        Verified: true,
        From: time.Now(),
    },
}
values, _ := encoder.Values(query)
fmt.Println(values.Encode()) //(unescaped) output: "user[from]=1601623397728&user[verified]=true"
```

By default, it uses the brackets, add the `dot` option to
a nested struct field to scope its children with `.`:
```go
type Query struct {
    User User `qs:"user,dot"`
}

values, _ := encoder.Values(query)
fmt.Println(values.Encode()) //(unescaped) output: "user.from=1601623397728&user.verified=true"
```
The `dot` option applies only to the field it is declared on; nest it again on a
deeper struct field to keep using dots (otherwise that level falls back to brackets).

### Custom Type
Implement funcs:
* `EncodeParam` to encode itself into query param.
* `IsZero` to check whether an object is zero to determine whether it should be omitted when encoding.
```go
type NullableName struct {
	First string
	Last  string
}

func (n NullableName) EncodeParam() (string, error) {
	return n.First + n.Last, nil
}

func (n NullableName) IsZero() bool {
	return n.First == "" && n.Last == ""
}

type Struct struct {
    User  NullableName `qs:"user"`
    Admin NullableName `qs:"admin,omitempty"`
}

s := Struct{
    User: NullableName{
        First: "son",
        Last:  "huynh",
    },
}
encoder := qs.NewEncoder()

values, err := encoder.Values(&s)
if err != nil {
    // Handle error
    fmt.Println("failed")
    return
}
fmt.Println(values.Encode()) //(unescaped) output: "user=sonhuynh"
```

### Limitation
- if elements in `slice/array` are `struct` data type, multi-level nesting are limited
- no decoder yet

_Will improve in future versions_ 

## License
Distributed under MIT License, please see license file in code for more details.