package surf

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"net/netip"
	"os"
	"os/signal"
	"path/filepath"
	"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/cooler"
	"git.golem15.com/golem15/summercms/modules/diary"
	"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.
// Once it listens it prints a startup summary on a terminal and logs it as
// records (component serve); on SIGINT or SIGTERM it drains requests and the
// in-process worker for up to 10 seconds, reports what it did and returns
// nil, or the drain errors.
func ServeCommand(app *backpack.App, plugins []party.Plugin) bonfire.Command {
	return bonfire.Command{
		Name:        "serve",
		Description: "Serve the application HTTP API",
		Long: `Opens the database and the uploads bucket, installs the cache, assembles every
plugin's routes, binds the address and starts the in-process job worker
(queue.work_in_serve). Once it listens it prints a startup summary: version,
environment, URL and admin URL, database and pending migrations, plugins, and
the queue, scheduler, mail, cache, realtime and search drivers. -v adds one
line per plugin; -q prints only warnings and errors. Off a terminal the same
facts are logged as a "startup summary" record and a "listening on <addr>"
record, so journald and the log files keep them.

Each request is logged as an "http request" record of component http (route
pattern, never the path). On Ctrl+C or SIGTERM serve drains requests and the
worker for up to 10 seconds and prints a short report. It exits 0 after a
clean stop and 1 when draining fails.`,
		Flags: []bonfire.Flag{{
			Name:        "addr",
			Description: "Listen address",
			Default:     ":8080",
		}},
		Examples: []bonfire.Example{
			{Command: "serve", Description: "Listen on every interface, port 8080"},
			{Command: "serve --addr 127.0.0.1:8096", Description: "Listen on loopback only, during development"},
			{Command: "serve -v", Description: "Add one summary line per plugin and info logs of every component"},
			{Command: "serve -q", Description: "Print only warnings and errors"},
		},
		Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
			started := time.Now()
			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()
			coolerHandle, err := installCooler(ctx, app)
			if err != nil {
				return err
			}
			defer coolerHandle.Close()
			r, err := BuildRouter(app, plugins)
			if err != nil {
				return err
			}
			h, err := r.compile()
			if err != nil {
				return err
			}
			counter := newRequestCounter(h)
			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
			}
			prefix, mounted := r.AdminPrefix()
			admins := adminsUnknown
			if mounted {
				admins = countAdmins(ctx, gdb)
			}
			pending, pendingErr := lagoon.PendingMigrations(gdb, plugins)
			facts := buildFacts(app, factInputs{
				addr:        listenAddr(addr, ln),
				bin:         binName(),
				plugins:     plugins,
				queues:      worker.Queues(),
				worker:      worker != nil,
				adminPrefix: prefix,
				mounted:     mounted,
				admins:      admins,
				pending:     pending,
				pendingErr:  pendingErr,
				version:     bonfire.BuildVersion(),
			})
			styled := bonfire.IsTerminal(out) && !bonfire.IsQuiet(out)
			logCtx := ctx
			if styled {
				printSummary(out, facts)
				logCtx = diary.HideOnTTY(ctx)
			}
			logSummary(logCtx, serveLog, facts)
			srv := &http.Server{Addr: addr, Handler: counter, 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():
				report := shutdownReport{Draining: counter.inFlight.Load()}
				if styled {
					out.Info(fmt.Sprintf("Shutting down: draining %d requests", report.Draining))
				}
				sctx, cancel := shutdownCtx()
				defer cancel()
				if err := srv.Shutdown(sctx); err != nil {
					report.Aborted = counter.inFlight.Load()
					_ = srv.Close()
					report.Errors = append(report.Errors, fmt.Errorf("surf: drain requests: %w", err))
				}
				if err := stopWorker(sctx, worker); err != nil {
					report.Errors = append(report.Errors, err)
				}
				if err := <-errCh; err != nil && err != http.ErrServerClosed {
					report.Errors = append(report.Errors, err)
				}
				if worker != nil {
					stats := worker.Stats()
					report.Worker = &stats
				}
				report.Served = counter.served.Load()
				report.Uptime = time.Since(started)
				reportCtx := context.WithoutCancel(ctx)
				if styled {
					bonfire.Details(out, "Shutdown report", report.details())
					reportCtx = diary.HideOnTTY(reportCtx)
				}
				logReport(reportCtx, serveLog, report)
				return report.Err()
			case err := <-errCh:
				sctx, cancel := shutdownCtx()
				defer cancel()
				workerErr := stopWorker(sctx, worker)
				if err != nil && err != http.ErrServerClosed {
					return err
				}
				return workerErr
			}
		},
	}
}

// listenAddr is addr, or the bound address when addr asks for any port.
func listenAddr(addr string, ln net.Listener) string {
	if _, port, err := net.SplitHostPort(addr); err == nil && port == "0" && ln != nil {
		return ln.Addr().String()
	}
	return addr
}

// binName is how a person runs this binary from the application root:
// bin/<name of the running executable>.
func binName() string {
	return "bin/" + filepath.Base(os.Args[0])
}

// 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, bonfire.WithHint(err,
			"serve stores uploads in the bucket named by storage.uploads.bucket_url in config/storage.yaml (or SUMMER_STORAGE__UPLOADS__BUCKET_URL).",
			"SUMMER_STORAGE__UPLOADS__BUCKET_URL=file://./storage/app/uploads {bin} serve")
	}
	if err := attach.Publish(app, bucket); err != nil {
		_ = bucket.Close()
		return nil, err
	}
	return bucket, nil
}

// installCooler installs cooler and, when http.rate_limit.store is redis,
// publishes its Redis-backed Store (falling back to a per-instance
// MemoryStore while Redis does not answer) so BuildRouter's limiter shares
// counters across instances. Only serve calls it: route:list never dials Redis.
func installCooler(ctx context.Context, app *backpack.App) (*cooler.Handle, error) {
	h, err := cooler.Install(ctx, app)
	if err != nil {
		return nil, err
	}
	if h.RateLimitRedis() {
		// longest bucket decay is 1 minute; sweep at 2x (as BuildRouter)
		if err := app.Publish[Store](h.RateLimitStore(NewMemoryStore(2 * time.Minute))); err != nil {
			_ = h.Close()
			return nil, fmt.Errorf("surf: %w", err)
		}
	}
	return h, 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 note; warn notes print with the warning symbol.
type bannerLine struct {
	warn bool
	text string
}

// adminStatus is the summary's Admin value and the notes printed after the
// summary: the admin URL (url is serve's browser URL, "" when the address
// does not parse) with a warning naming summer admin:create when no
// administrator exists yet, or "off" with the steps to add an admin
// controller.
func adminStatus(url, adminPrefix string, mounted bool, admins adminPresence) (string, []bannerLine) {
	if !mounted {
		return strings.TrimPrefix(adminOffText, "admin: "), []bannerLine{
			{text: "to add an admin, 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"},
		}
	}
	value := "mounted at " + adminPrefix
	if url != "" {
		value = strings.TrimSuffix(url, "/") + adminPrefix
	}
	switch admins {
	case adminsNone:
		return value, []bannerLine{{warn: true, text: "no administrators yet; create one with " + adminCreateCommand}}
	case adminsMissingTable:
		return value, []bannerLine{{warn: true, text: "the admin tables do not exist yet; run summer migrate, then " + adminCreateCommand}}
	case adminsUnknown:
		return value, []bannerLine{{text: "sign in with an administrator; " + adminCreateCommand + " creates one"}}
	}
	return value, nil
}

// printBanner writes notes 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)
	}
}