package eghttp

import (
	"context"
	"errors"
	"net"
	"net/http"
	"strconv"
	"time"

	"git.blauwelle.com/go/crate/log"
)

const (
	DefaultAddr              = ":8080"
	DefaultReadHeaderTimeout = time.Second
)

type Option interface {
	apply(cfg *config)
}

func WithPort(port int) Option {
	return optionFunc(func(cfg *config) {
		cfg.server.Addr = net.JoinHostPort("", strconv.Itoa(port))
	})
}

func WithHandler(handler http.Handler) Option {
	return optionFunc(func(cfg *config) {
		cfg.server.Handler = handler
	})
}

// WithServer 指定要启动的服务器. 注意会替换原有的服务器, 导致早前配置服务器相关的 [Option] 失效.
func WithServer(server *http.Server) Option {
	return optionFunc(func(cfg *config) {
		cfg.server = server
	})
}

func WithStartFn(fn func(server *http.Server) error) Option {
	return optionFunc(func(cfg *config) {
		cfg.startFn = fn
	})
}

// WithServerOption 使用 fn 配置 [http.Server];
func WithServerOption(fn func(server *http.Server)) Option {
	return optionFunc(func(cfg *config) {
		fn(cfg.server)
	})
}

// WithShutdownTimeout 设置关闭服务的超时时间. <0 没有最长等待时间.
func WithShutdownTimeout(timeout time.Duration) Option {
	return optionFunc(func(cfg *config) {
		cfg.shutdownTimeout = timeout
	})
}

type config struct {
	server          *http.Server
	startFn         func(server *http.Server) error
	shutdownTimeout time.Duration
}

func newDefaultConfig() *config {
	return &config{
		server: &http.Server{
			Addr:              DefaultAddr,
			ReadHeaderTimeout: DefaultReadHeaderTimeout,
		},
		startFn: func(server *http.Server) error {
			return server.ListenAndServe()
		},
		shutdownTimeout: -1,
	}
}

type optionFunc func(cfg *config)

func (fn optionFunc) apply(cfg *config) {
	fn(cfg)
}

// ListenAndServe 构造1个函数, 启动 [http.Server] 并受 ctx 控制终止.
func ListenAndServe(opts ...Option) func(ctx context.Context) error {
	cfg := newDefaultConfig()
	for _, opt := range opts {
		opt.apply(cfg)
	}
	errChan := make(chan error, 2) //nolint:gomnd
	return func(ctx context.Context) error {
		go func() {
			err := cfg.startFn(cfg.server)
			log.Tracef(ctx, "server return with %s", err)
			if !errors.Is(err, http.ErrServerClosed) {
				errChan <- err
			}
		}()
		go func() {
			<-ctx.Done()
			shutdownCtx := context.Background()
			if cfg.shutdownTimeout >= 0 {
				var cancel func()
				shutdownCtx, cancel = context.WithTimeout(shutdownCtx, cfg.shutdownTimeout)
				defer cancel()
			}
			errChan <- cfg.server.Shutdown(shutdownCtx)
		}()
		return <-errChan
	}
}