package surf

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"net/netip"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bonfire"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"git.golem15.com/golem15/summercms/modules/conga"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"git.golem15.com/golem15/summercms/modules/party"
	"gocloud.dev/blob"
	"gorm.io/gorm"
)

// ServeCommand starts a signal-aware HTTP server on the assembled router.
func ServeCommand(app *backpack.App, plugins []party.Plugin) bonfire.Command {
	return bonfire.Command{
		Name:        "serve",
		Description: "Serve the application HTTP API",
		Flags: []bonfire.Flag{{
			Name:        "addr",
			Description: "Listen address",
			Default:     ":8080",
		}},
		Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
			addr, _ := in.Flag("addr")
			if strings.TrimSpace(addr) == "" {
				addr = ":8080"
			}
			ctx, stop := signal.NotifyContext(ctx, os.Interrupt, syscall.SIGTERM)
			defer stop()
			sqlDB, gdb, err := lagoon.OpenFromApp(ctx, app)
			if err != nil {
				return err
			}
			defer sqlDB.Close()
			if err := lagoon.Publish(app, sqlDB, gdb); err != nil {
				return err
			}
			bucket, err := publishUploads(ctx, app)
			if err != nil {
				return err
			}
			defer bucket.Close()
			r, err := BuildRouter(app, plugins)
			if err != nil {
				return err
			}
			h, err := r.compile()
			if err != nil {
				return err
			}
			ln, err := net.Listen("tcp", addr)
			if err != nil {
				return err
			}
			worker, err := conga.StartServeWorker(ctx, app, plugins)
			if err != nil {
				_ = ln.Close()
				return err
			}
			if worker != nil {
				out.Info(fmt.Sprintf("job worker started on queues: %s", strings.Join(worker.Queues(), ", ")))
			}
			prefix, mounted := r.AdminPrefix()
			admins := adminsUnknown
			if mounted {
				admins = countAdmins(ctx, gdb)
			}
			printBanner(out, serveBanner(addr, prefix, mounted, admins))
			srv := &http.Server{Addr: addr, Handler: h, BaseContext: func(net.Listener) context.Context { return ctx }}
			errCh := make(chan error, 1)
			go func() {
				errCh <- srv.Serve(ln)
			}()
			shutdownCtx := func() (context.Context, context.CancelFunc) {
				return context.WithTimeout(context.Background(), 10*time.Second)
			}
			select {
			case <-ctx.Done():
				sctx, cancel := shutdownCtx()
				defer cancel()
				shutdownErr := srv.Shutdown(sctx)
				workerErr := stopWorker(sctx, worker)
				if shutdownErr != nil {
					return shutdownErr
				}
				err := <-errCh
				if err != nil && err != http.ErrServerClosed {
					return err
				}
				return workerErr
			case err := <-errCh:
				sctx, cancel := shutdownCtx()
				defer cancel()
				workerErr := stopWorker(sctx, worker)
				if err != nil && err != http.ErrServerClosed {
					return err
				}
				return workerErr
			}
		},
	}
}

// stopWorker stops the in-process job worker, if serve started one.
func stopWorker(ctx context.Context, w *conga.Worker) error {
	if w == nil {
		return nil
	}
	return w.Stop(ctx)
}

// publishUploads opens storage.uploads.bucket_url and publishes *blob.Bucket.
// An empty URL fails boot the same way an empty JWT secret does.
func publishUploads(ctx context.Context, app *backpack.App) (*blob.Bucket, error) {
	if app == nil {
		return nil, fmt.Errorf("surf: app is nil")
	}
	bucket, err := attach.OpenBucket(ctx, app.Config)
	if err != nil {
		return nil, err
	}
	if err := attach.Publish(app, bucket); err != nil {
		_ = bucket.Close()
		return nil, err
	}
	return bucket, nil
}

// adminCreateCommand is the command the startup hints name for creating the
// first backend administrator.
const adminCreateCommand = "summer admin:create --email you@example.com --superuser"

// adminOffText is the admin status line serve and route:list print when no
// plugin registers an admin controller.
const adminOffText = "admin: off — no plugin registers an admin controller"

// serveURL turns a listen address into a URL a browser can open. An empty or
// unspecified host (0.0.0.0, ::) becomes 127.0.0.1, port 80 is left out and
// an IPv6 host is bracketed. An address that does not parse gives "".
func serveURL(addr string) string {
	host, port, err := net.SplitHostPort(addr)
	if err != nil || port == "" {
		return ""
	}
	if host == "" {
		host = "127.0.0.1"
	} else if ip, err := netip.ParseAddr(host); err == nil && ip.IsUnspecified() {
		host = "127.0.0.1"
	}
	hostport := net.JoinHostPort(host, port)
	if port == "80" {
		hostport = host
		if strings.Contains(host, ":") {
			hostport = "[" + host + "]"
		}
	}
	return "http://" + hostport + "/"
}

// adminPresence is what serve could learn about backend administrators.
type adminPresence int

const (
	adminsUnknown adminPresence = iota
	adminsMissingTable
	adminsNone
	adminsPresent
)

// countAdmins checks whether backend_users exists and holds a row. It is
// bounded by a 2 second timeout and maps every failure to adminsUnknown, so
// it never fails or blocks boot. HasTable queries information_schema, so a
// missing table does not reach the GORM error log.
func countAdmins(ctx context.Context, gdb *gorm.DB) adminPresence {
	if gdb == nil {
		return adminsUnknown
	}
	c, cancel := context.WithTimeout(ctx, 2*time.Second)
	defer cancel()
	db := gdb.WithContext(c)
	if !db.Migrator().HasTable(&cabana.BackendUser{}) {
		if c.Err() != nil {
			return adminsUnknown
		}
		return adminsMissingTable
	}
	var n int64
	if err := db.Model(&cabana.BackendUser{}).Count(&n).Error; err != nil {
		return adminsUnknown
	}
	if n == 0 {
		return adminsNone
	}
	return adminsPresent
}

// bannerLine is one startup line; warn lines print with the warning symbol.
type bannerLine struct {
	warn bool
	text string
}

// serveBanner builds the lines serve prints once the port is bound: the
// listen address with a browser URL, then the admin status.
func serveBanner(addr, adminPrefix string, mounted bool, admins adminPresence) []bannerLine {
	url := serveURL(addr)
	listen := "listening on " + addr
	if url != "" {
		listen += ", open " + url
	}
	lines := []bannerLine{{text: listen}}
	if !mounted {
		return append(lines,
			bannerLine{text: adminOffText},
			bannerLine{text: "to add one, run summer make:admin-controller <vendor.plugin> <Name>, then summer build, summer migrate and " + adminCreateCommand + "; the admin needs SUMMER_ADMIN__JWT__SECRET, which summer new writes to .env"},
		)
	}
	if url != "" {
		lines = append(lines, bannerLine{text: "admin: " + strings.TrimSuffix(url, "/") + adminPrefix})
	} else {
		lines = append(lines, bannerLine{text: "admin: mounted at " + adminPrefix})
	}
	switch admins {
	case adminsNone:
		lines = append(lines, bannerLine{warn: true, text: "no administrators yet; create one with " + adminCreateCommand})
	case adminsMissingTable:
		lines = append(lines, bannerLine{warn: true, text: "the admin tables do not exist yet; run summer migrate, then " + adminCreateCommand})
	case adminsUnknown:
		lines = append(lines, bannerLine{text: "sign in with an administrator; " + adminCreateCommand + " creates one"})
	}
	return lines
}

// printBanner writes banner lines as info or warning output.
func printBanner(out bonfire.Output, lines []bannerLine) {
	for _, l := range lines {
		if l.warn {
			out.Warning(l.text)
			continue
		}
		out.Info(l.text)
	}
}