package surf

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"strconv"
	"strings"
	"sync/atomic"
	"time"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bonfire"
	"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/party"
)

// serveLog is the logger of serve's startup summary and shutdown report.
var serveLog = diary.For("serve")

// Messages of the records serve logs.
const (
	summaryMessage = "startup summary"
	reportMessage  = "shutdown report"
	listenPrefix   = "listening on "
)

// requestCounter wraps the compiled handler and counts requests in flight
// and served, whatever http.access_log says, for the shutdown report.
type requestCounter struct {
	next     http.Handler
	inFlight atomic.Int64
	served   atomic.Int64
}

func newRequestCounter(next http.Handler) *requestCounter {
	return &requestCounter{next: next}
}

func (c *requestCounter) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	c.inFlight.Add(1)
	defer func() {
		c.inFlight.Add(-1)
		c.served.Add(1)
	}()
	c.next.ServeHTTP(w, req)
}

// pluginFact is one plugin's line of the verbose summary.
type pluginFact struct {
	ID       string
	Requires []string
	Pending  int
}

// summaryFacts is what serve reports once it is listening. It holds no DSN,
// user, password, key or token: the database is its host, port and name.
type summaryFacts struct {
	Header      string
	Environment string
	Addr        string
	URL         string
	Admin       string
	AdminNotes  []bannerLine
	Database    string
	// Pending is the number of pending migrations; -1 when it could not
	// be read.
	Pending    int
	MigrateCmd string
	Plugins    []pluginFact
	Queue      string
	Scheduler  string
	Mail       string
	Cache      string
	Realtime   string
	Search     string
}

// factInputs are the values serve learned while booting.
type factInputs struct {
	addr        string
	bin         string
	plugins     []party.Plugin
	queues      []string
	worker      bool
	adminPrefix string
	mounted     bool
	admins      adminPresence
	pending     []lagoon.MigrationRef
	pendingErr  error
	version     bonfire.Version
}

// buildFacts collects the summary from the app's config and in.
func buildFacts(app *backpack.App, in factInputs) summaryFacts {
	name := strings.TrimSpace(configString(app, "app.name"))
	if name == "" {
		name = strings.TrimPrefix(in.bin, "bin/")
	}
	f := summaryFacts{
		Header:      in.version.Header(name),
		Environment: "unknown",
		Addr:        in.addr,
		URL:         serveURL(in.addr),
		Database:    lagoon.DatabaseLabel(configString(app, "database.dsn")),
		Pending:     len(in.pending),
		MigrateCmd:  in.bin + " migrate",
		Mail:        driverFact(app, "mail.driver", "memory"),
		Cache:       driverFact(app, cooler.CacheDriverKey, "memory"),
		Realtime:    driverFact(app, "realtime.driver", "null"),
		Search:      driverFact(app, "search.driver", "null"),
	}
	if app != nil && app.Config != nil && app.Config.Environment() != "" {
		f.Environment = app.Config.Environment()
	}
	if in.pendingErr != nil {
		f.Pending = -1
	}
	f.Admin, f.AdminNotes = adminStatus(f.URL, in.adminPrefix, in.mounted, in.admins)
	perPlugin := map[string]int{}
	for _, ref := range in.pending {
		perPlugin[ref.Plugin]++
	}
	for _, p := range in.plugins {
		f.Plugins = append(f.Plugins, pluginFact{ID: p.ID(), Requires: p.Requires(), Pending: perPlugin[p.ID()]})
	}
	if in.worker {
		f.Queue = strings.Join(in.queues, ", ") + " (worker in serve)"
		f.Scheduler = "in serve"
	} else {
		f.Queue = "off in serve (queue.work_in_serve is false; run queue:work)"
		f.Scheduler = "off in serve (run schedule:run)"
	}
	return f
}

func configString(app *backpack.App, key string) string {
	if app == nil || app.Config == nil {
		return ""
	}
	return app.Config.String(key)
}

// driverFact is the lower-cased driver named by key, or def when empty.
func driverFact(app *backpack.App, key, def string) string {
	if v := strings.ToLower(strings.TrimSpace(configString(app, key))); v != "" {
		return v
	}
	return def
}

// migrations is the migration line: "up to date", "N pending — run ..." or
// "unknown".
func (f summaryFacts) migrations() (string, bool) {
	switch {
	case f.Pending < 0:
		return "unknown (the migration history could not be read)", true
	case f.Pending == 0:
		return "up to date", false
	default:
		return fmt.Sprintf("%d pending — run %s", f.Pending, f.MigrateCmd), true
	}
}

func (f summaryFacts) pluginIDs() []string {
	ids := make([]string, 0, len(f.Plugins))
	for _, p := range f.Plugins {
		ids = append(ids, p.ID)
	}
	return ids
}

// details is the block printed on a terminal; verbosity 1 or more adds one
// line per plugin with its required plugins and pending migrations.
func (f summaryFacts) details(verbosity int) []bonfire.Detail {
	url := f.URL
	if url == "" {
		url = f.Addr
	}
	migrations, warn := f.migrations()
	plugins := strconv.Itoa(len(f.Plugins))
	if len(f.Plugins) > 0 {
		plugins += " (" + strings.Join(f.pluginIDs(), ", ") + ")"
	}
	rows := []bonfire.Detail{
		{Label: "Environment", Value: f.Environment},
		{Label: "URL", Value: url},
		{Label: "Admin", Value: f.Admin},
		{Label: "Database", Value: f.Database},
		{Label: "Migrations", Value: migrations, Warn: warn},
		{Label: "Plugins", Value: plugins},
	}
	if verbosity >= 1 {
		for _, p := range f.Plugins {
			requires := "requires nothing"
			if len(p.Requires) > 0 {
				requires = "requires " + strings.Join(p.Requires, ", ")
			}
			rows = append(rows, bonfire.Detail{
				Label: "  " + p.ID,
				Value: fmt.Sprintf("%s; %d pending migrations", requires, p.Pending),
				Warn:  p.Pending > 0,
			})
		}
	}
	return append(rows,
		bonfire.Detail{Label: "Queue", Value: f.Queue},
		bonfire.Detail{Label: "Scheduler", Value: f.Scheduler},
		bonfire.Detail{Label: "Mail", Value: f.Mail},
		bonfire.Detail{Label: "Cache", Value: f.Cache},
		bonfire.Detail{Label: "Realtime", Value: f.Realtime},
		bonfire.Detail{Label: "Search", Value: f.Search},
	)
}

// attrs are the attributes of the "startup summary" record.
func (f summaryFacts) attrs() []slog.Attr {
	return []slog.Attr{
		slog.String("app", f.Header),
		slog.String("environment", f.Environment),
		slog.String("url", f.URL),
		slog.String("admin", f.Admin),
		slog.String("database", f.Database),
		slog.Int("migrations_pending", f.Pending),
		slog.Int("plugins", len(f.Plugins)),
		slog.String("plugin_ids", strings.Join(f.pluginIDs(), ",")),
		slog.String("queue", f.Queue),
		slog.String("scheduler", f.Scheduler),
		slog.String("mail", f.Mail),
		slog.String("cache", f.Cache),
		slog.String("realtime", f.Realtime),
		slog.String("search", f.Search),
	}
}

// printSummary prints the block and the admin notes through out.
func printSummary(out bonfire.Output, f summaryFacts) {
	bonfire.Details(out, f.Header, f.details(bonfire.VerbosityOf(out)))
	printBanner(out, f.AdminNotes)
}

// logSummary logs one INFO record "startup summary" with every fact, one
// whose message is exactly "listening on <addr>" (application smoke scripts
// wait for it) and the admin notes (warnings at WARN).
func logSummary(ctx context.Context, log *slog.Logger, f summaryFacts) {
	log.LogAttrs(ctx, slog.LevelInfo, summaryMessage, f.attrs()...)
	log.LogAttrs(ctx, slog.LevelInfo, listenPrefix+f.Addr, slog.String("url", f.URL))
	for _, n := range f.AdminNotes {
		level := slog.LevelInfo
		if n.warn {
			level = slog.LevelWarn
		}
		log.LogAttrs(ctx, level, n.text)
	}
}

// shutdownReport is what serve did, printed and logged after a signal.
type shutdownReport struct {
	// Draining is the number of requests in flight when the signal came.
	Draining int64
	// Aborted is the number still running at the drain deadline.
	Aborted int64
	Served  int64
	Worker  *conga.WorkerStats
	Uptime  time.Duration
	Errors  []error
}

// Drained is the number of in-flight requests that finished in time.
func (r shutdownReport) Drained() int64 {
	return max(0, r.Draining-r.Aborted)
}

// Err joins the drain errors; nil means a clean stop (exit 0).
func (r shutdownReport) Err() error {
	return errors.Join(r.Errors...)
}

func (r shutdownReport) requestsLine() string {
	return fmt.Sprintf("%d served, %d drained, %d aborted", r.Served, r.Drained(), r.Aborted)
}

func workerLine(s *conga.WorkerStats) string {
	if s == nil {
		return "not running in serve"
	}
	return fmt.Sprintf("%d done, %d failed, %d handed back to the queue", s.Done, s.Failed, s.HandedBack+s.InFlight)
}

func errorsLine(errs []error) string {
	if len(errs) == 0 {
		return "none"
	}
	parts := make([]string, 0, len(errs))
	for _, e := range errs {
		parts = append(parts, e.Error())
	}
	return strings.Join(parts, "; ")
}

// uptime rounds d for the report.
func uptime(d time.Duration) string {
	switch {
	case d >= time.Minute:
		return d.Round(time.Second).String()
	case d >= time.Second:
		return d.Round(100 * time.Millisecond).String()
	default:
		return d.Round(time.Millisecond).String()
	}
}

// details is the report as label/value lines.
func (r shutdownReport) details() []bonfire.Detail {
	return []bonfire.Detail{
		{Label: "Requests", Value: r.requestsLine(), Warn: r.Aborted > 0},
		{Label: "Worker", Value: workerLine(r.Worker)},
		{Label: "Uptime", Value: uptime(r.Uptime)},
		{Label: "Errors", Value: errorsLine(r.Errors), Warn: len(r.Errors) > 0},
	}
}

// attrs are the attributes of the "shutdown report" record.
func (r shutdownReport) attrs() []slog.Attr {
	attrs := []slog.Attr{
		slog.Int64("served", r.Served),
		slog.Int64("drained", r.Drained()),
		slog.Int64("aborted", r.Aborted),
		slog.Int64("uptime_ms", r.Uptime.Milliseconds()),
	}
	if r.Worker != nil {
		attrs = append(attrs,
			slog.Int64("jobs_done", r.Worker.Done),
			slog.Int64("jobs_failed", r.Worker.Failed),
			slog.Int64("jobs_handed_back", r.Worker.HandedBack+r.Worker.InFlight),
		)
	}
	if len(r.Errors) > 0 {
		attrs = append(attrs, slog.String("errors", errorsLine(r.Errors)))
	}
	return attrs
}

// logReport logs the report as one record: INFO, or ERROR with drain errors.
func logReport(ctx context.Context, log *slog.Logger, r shutdownReport) {
	level := slog.LevelInfo
	if len(r.Errors) > 0 {
		level = slog.LevelError
	}
	log.LogAttrs(ctx, level, reportMessage, r.attrs()...)
}