package conga

import (
	"context"
	"fmt"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/bonfire"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/party"
	"github.com/riverqueue/river"
	"github.com/riverqueue/river/rivertype"
	"gorm.io/gorm"
)

// clearBatch is the number of jobs one JobDeleteMany pass removes.
const clearBatch = 10000

// RuntimeCommands returns the queue:work, schedule:run and queue:clear
// commands for the application binary.
func RuntimeCommands(app *backpack.App, plugins []party.Plugin) []bonfire.Command {
	return []bonfire.Command{
		{
			Name:        "queue:work",
			Description: "Run background job workers in the foreground",
			Flags: []bonfire.Flag{{
				Name:        "queue",
				Description: "Queue to work (repeatable; default all known queues)",
				Repeatable:  true,
			}},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				return withDB(ctx, app, func() error {
					return work(ctx, app, plugins, in.Flags("queue"), out)
				})
			},
		},
		{
			Name:        "schedule:run",
			Description: "Run the scheduler in the foreground (or once for system cron)",
			Flags: []bonfire.Flag{{
				Name:        "once",
				Description: "Run the entries due this minute and exit (for system cron)",
				Bare:        true,
			}},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				if v, ok := in.Flag("once"); ok {
					if once, _ := strconv.ParseBool(v); once {
						return scheduleRunOnce(ctx, app, plugins, scheduleNow(), out)
					}
				}
				return withDB(ctx, app, func() error {
					return runScheduler(ctx, app, plugins, out)
				})
			},
		},
		{
			Name:        "queue:clear",
			Description: "Clear all queued jobs, by deleting all pending jobs.",
			Args: []bonfire.Arg{{
				Name:        "queue",
				Description: "The name of the queue to clear (default \"default\")",
			}},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				queue, _ := in.Argument("queue")
				queue = strings.TrimSpace(queue)
				if queue == "" {
					queue = defaultQueue
				}
				return withDB(ctx, app, func() error {
					return clearQueue(ctx, app, queue, out)
				})
			},
		},
	}
}

func work(ctx context.Context, app *backpack.App, plugins []party.Plugin, queues []string, out bonfire.Output) error {
	ctx, stop := signal.NotifyContext(ctx, os.Interrupt, syscall.SIGTERM)
	defer stop()
	w, err := StartWorker(ctx, app, plugins, WorkerOptions{Queues: queues})
	if err != nil {
		return err
	}
	out.Info("worker started on queues: " + strings.Join(w.Queues(), ", "))
	<-ctx.Done()
	stopCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	return w.Stop(stopCtx)
}

// runScheduler runs a scheduler-only worker (the scheduled queue plus every
// plugin's periodic jobs) until SIGINT or SIGTERM.
func runScheduler(ctx context.Context, app *backpack.App, plugins []party.Plugin, out bonfire.Output) error {
	ctx, stop := signal.NotifyContext(ctx, os.Interrupt, syscall.SIGTERM)
	defer stop()
	w, err := StartWorker(ctx, app, plugins, WorkerOptions{Queues: []string{QueueScheduled}})
	if err != nil {
		return err
	}
	out.Info("scheduler started")
	<-ctx.Done()
	stopCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	return w.Stop(stopCtx)
}

// scheduleRunOnce runs, without River, every schedule entry due in the
// minute of now in app.timezone (Laravel schedule:run for system cron). An
// unregistered command is warned about and skipped; the returned error is the
// first command error, after every due entry ran.
func scheduleRunOnce(ctx context.Context, app *backpack.App, plugins []party.Plugin, now time.Time, out bonfire.Output) error {
	entries, err := scheduleEntries(app, plugins)
	if err != nil {
		return err
	}
	loc, err := appLocation(app)
	if err != nil {
		return err
	}
	local := now.In(loc)
	var due []scheduleEntry
	for _, e := range entries {
		if dueAt(e.cmd.Cadence, local) {
			due = append(due, e)
		}
	}
	if len(due) == 0 {
		out.Println("No scheduled commands are ready to run.")
		return nil
	}
	return withAppDB(ctx, app, func() error {
		log := loggerFromApp(app)
		var first error
		for _, e := range due {
			if _, ok := scheduledCatalog(app, log, e.cmd.Command); !ok {
				out.Warning(fmt.Sprintf("Scheduled command %s is not registered; skipping", e.cmd.Command))
				continue
			}
			out.Printf("Running scheduled command: %s\n", strings.Join(append([]string{e.cmd.Command}, e.cmd.Args...), " "))
			if _, err := callScheduled(ctx, app, log, e.cmd.Command, e.cmd.Args, out); err != nil && first == nil {
				first = err
			}
		}
		return first
	})
}

// dueAt reports whether a cadence is due in the wall-clock minute of t: a
// daily cadence at its hour and minute, Every(d) of a minute or less on every
// run, and a longer Every(d) when the minutes since midnight are a multiple
// of d.
func dueAt(c pact.Cadence, t time.Time) bool {
	if h, m, ok := c.At(); ok {
		return t.Hour() == h && t.Minute() == m
	}
	d := c.Interval()
	if d <= 0 {
		return false
	}
	if d <= time.Minute {
		return true
	}
	sinceMidnight := time.Duration(t.Hour()*60+t.Minute()) * time.Minute
	return sinceMidnight%d == 0
}

// withAppDB runs fn with the app's database: the published one when there is
// one, otherwise one opened for the command the way withDB does.
func withAppDB(ctx context.Context, app *backpack.App, fn func() error) error {
	if gdb, ok := app.Lookup[*gorm.DB](); ok && gdb != nil {
		return fn()
	}
	return withDB(ctx, app, fn)
}

// clearQueue deletes the available, scheduled and retryable jobs of queue in
// batches until a pass deletes none. River never deletes running jobs.
func clearQueue(ctx context.Context, app *backpack.App, queue string, out bonfire.Output) error {
	m, err := From(app)
	if err != nil {
		return err
	}
	client, err := m.insertClient()
	if err != nil {
		return err
	}
	out.Info(fmt.Sprintf("Clearing queue %q", queue))
	total := 0
	for {
		res, err := client.JobDeleteMany(ctx, river.NewJobDeleteManyParams().
			Queues(queue).
			States(rivertype.JobStateAvailable, rivertype.JobStateScheduled, rivertype.JobStateRetryable).
			First(clearBatch))
		if err != nil {
			return fmt.Errorf("conga: clear queue %q: %w", queue, err)
		}
		if len(res.Jobs) == 0 {
			break
		}
		total += len(res.Jobs)
	}
	out.Info(fmt.Sprintf("Cleared %d jobs", total))
	return nil
}

// withDB opens and publishes the shared pool for a CLI command and closes it
// when fn returns, the way lagoon's own commands do.
func withDB(ctx context.Context, app *backpack.App, fn func() error) error {
	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
	}
	return fn()
}