package server

import (
	"errors"
	"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(status int, messages ...any) error
	Get(param string) string
	Reader(io.Reader) error
	Request() Request
	Response() Response
	String(string) error
}

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

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

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

// Error is used for sending error messages to the client.
func (ctx *ctx) Error(status int, messages ...any) error {
	var combined []error

	for _, msg := range messages {
		switch err := msg.(type) {
		case error:
			combined = append(combined, err)
		case string:
			combined = append(combined, errors.New(err))
		}
	}

	ctx.response.WriteHeader(status)
	return errors.Join(combined...)
}

// Get retrieves a parameter.
func (ctx *ctx) Get(param string) string {
	for i := 0; i < ctx.paramCount; i++ {
		if ctx.paramNames[i] == param {
			return ctx.paramValues[i]
		}
	}

	return ""
}

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

// Request returns the HTTP request.
func (ctx *ctx) Request() Request {
	return &ctx.request
}

// Response returns the HTTP response.
func (ctx *ctx) Response() Response {
	return &ctx.response
}

// String responds with the given string.
func (ctx *ctx) 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 *ctx) addParameter(name string, value string) {
	ctx.paramNames[ctx.paramCount] = name
	ctx.paramValues[ctx.paramCount] = value
	ctx.paramCount++
}