package server

import (
	"io"
	"net/http"
	"unsafe"
)

// maxParams defines the maximum number of parameters per route.
const maxParams = 16

// Context represents the interface for a request & response context.
type Context interface {
	Bytes([]byte) error
	Error(int, error) error
	Reader(io.Reader) error
	String(string) error
}

// context represents a request & response context.
type context struct {
	request     *http.Request
	response    http.ResponseWriter
	paramNames  [maxParams]string
	paramValues [maxParams]string
	paramCount  int
}

// newContext returns a new context from the pool.
func newContext(request *http.Request, response http.ResponseWriter) *context {
	ctx := contextPool.Get().(*context)
	ctx.request = request
	ctx.response = response
	ctx.paramCount = 0
	return ctx
}

// Bytes responds with a raw byte slice.
func (ctx *context) Bytes(body []byte) error {
	_, err := ctx.response.Write(body)
	return err
}

// Error is used for sending error messages to the client.
func (ctx *context) Error(status int, err error) error {
	ctx.response.WriteHeader(status)
	return err
}

// Reader sends the contents of the io.Reader without creating an in-memory copy.
func (ctx *context) Reader(reader io.Reader) error {
	_, err := io.Copy(ctx.response, reader)
	return err
}

// String responds with the given string.
func (ctx *context) String(body string) error {
	slice := unsafe.Slice(unsafe.StringData(body), len(body))
	return ctx.Bytes(slice)
}

// addParameter adds a new parameter to the context.
func (ctx *context) addParameter(name string, value string) {
	ctx.paramNames[ctx.paramCount] = name
	ctx.paramValues[ctx.paramCount] = value
	ctx.paramCount++
}