// Copyright (c) 2020-{{.ToYear}} Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package atomic

{{ with .Imports }}
import (
	{{ range . -}}
		{{ printf "%q" . }}
	{{ end }}
)
{{ end }}

// {{ .Name }} is an atomic type-safe wrapper for {{ .Type }} values.
type {{ .Name }} struct{
	_ nocmp // disallow non-atomic comparison

	v {{ .Wrapped }}
}

var _zero{{ .Name }} {{ .Type }}


// New{{ .Name }} creates a new {{ .Name }}.
func New{{ .Name }}(val {{ .Type }}) *{{ .Name }} {
	x := &{{ .Name }}{}
	if val != _zero{{ .Name }} {
		x.Store(val)
	}
	return x
}

// Load atomically loads the wrapped {{ .Type }}.
func (x *{{ .Name }}) Load() {{ .Type }} {
	{{ if .Unpack -}}
		return {{ .Unpack }}(x.v.Load())
	{{- else -}}
		if v := x.v.Load(); v != nil {
			return v.({{ .Type }})
		}
		return _zero{{ .Name }}
	{{- end }}
}

// Store atomically stores the passed {{ .Type }}.
func (x *{{ .Name }}) Store(val {{ .Type }}) {
	x.v.Store({{ .Pack }}(val))
}

{{ if .CAS -}}
	// CAS is an atomic compare-and-swap for {{ .Type }} values.
	//
	// Deprecated: Use CompareAndSwap.
	func (x *{{ .Name }}) CAS(old, new {{ .Type }}) (swapped bool) {
		return x.CompareAndSwap(old, new)
	}
{{- end }}

{{ if .CompareAndSwap -}}
	// CompareAndSwap is an atomic compare-and-swap for {{ .Type }} values.
	func (x *{{ .Name }}) CompareAndSwap(old, new {{ .Type }}) (swapped bool) {
	 	{{ if eq .Wrapped "Value" -}}
			if x.v.CompareAndSwap({{ .Pack }}(old), {{ .Pack }}(new)) {
				return true
			}

			if old == _zero{{ .Name }} {
				// If the old value is the empty value, then it's possible the 
				// underlying Value hasn't been set and is nil, so retry with nil.
				return x.v.CompareAndSwap(nil, {{ .Pack }}(new))
			}

			return false
		{{- else -}}
			return x.v.CompareAndSwap({{ .Pack }}(old), {{ .Pack }}(new))
		{{- end }}
	}
{{- end }}

{{ if .Swap -}}
	// Swap atomically stores the given {{ .Type }} and returns the old
	// value.
	func (x *{{ .Name }}) Swap(val {{ .Type }}) (old {{ .Type }}) {
		return {{ .Unpack }}(x.v.Swap({{ .Pack }}(val)))
	}
{{- end }}

{{ if .JSON -}}
	// MarshalJSON encodes the wrapped {{ .Type }} into JSON.
	func (x *{{ .Name }}) MarshalJSON() ([]byte, error) {
		return json.Marshal(x.Load())
	}

	// UnmarshalJSON decodes a {{ .Type }} from JSON.
	func (x *{{ .Name }}) UnmarshalJSON(b []byte) error {
		var v {{ .Type }}
		if err := json.Unmarshal(b, &v); err != nil {
			return err
		}
		x.Store(v)
		return nil
	}
{{- end }}