package lagoon

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"reflect"
	"strconv"
	"strings"
	"time"

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

// Flags shared by the migration commands; each destructive command declares
// its own --force.
var (
	pretendFlag = bonfire.Flag{Name: "pretend", Description: "Show what would change without changing anything", Bare: true}
	jsonFlag    = bonfire.Flag{Name: "json", Description: "Print the result as JSON", Bare: true}
)

// forceDescription describes the --force flag of the destructive commands.
const forceDescription = "Skip the confirmation asked in production on a terminal"

// flagOn reports whether the bare flag name is set; a nil Input has none.
func flagOn(in bonfire.Input, name string) bool {
	if in == nil {
		return false
	}
	v, ok := in.Flag(name)
	if !ok {
		return false
	}
	on, _ := strconv.ParseBool(v)
	return on
}

// confirmProduction asks question before a destructive step when the
// environment is production and out is an interactive terminal, unless
// --force is set (D-28). Off a terminal, under -n or -q and in
// bonfire.Call it never asks, so deploys over SSH proceed as before. A
// "no" prints cancelled and returns a Reported error (exit 1).
func confirmProduction(app *backpack.App, in bonfire.Input, out bonfire.Output, question, cancelled string) error {
	if flagOn(in, "force") || app == nil || app.Config == nil || app.Config.Environment() != "production" {
		return nil
	}
	ok, err := bonfire.ConfirmProceed(out, question)
	if err != nil {
		return err
	}
	if !ok {
		out.Warning(cancelled)
		return bonfire.Reported(errors.New(cancelled))
	}
	return nil
}

// lastApplied is the last migration of pluginID, in declaration order, that
// its history table holds; "" when none is applied.
func lastApplied(gdb *gorm.DB, plugins []party.Plugin, pluginID string) (string, error) {
	var target party.Plugin
	for _, p := range plugins {
		if p.ID() == pluginID {
			target = p
			break
		}
	}
	if target == nil {
		return "", fmt.Errorf("%w: %q", ErrUnknownPlugin, pluginID)
	}
	hm, ok := target.(pact.HasMigrations)
	if !ok || len(hm.Migrations()) == 0 {
		return "", fmt.Errorf("%w: %q", ErrNoMigrations, pluginID)
	}
	table, err := HistoryTableName(pluginID)
	if err != nil {
		return "", err
	}
	if !gdb.Migrator().HasTable(table) {
		return "", nil
	}
	var ids []string
	if err := gdb.Table(table).Pluck("id", &ids).Error; err != nil {
		return "", fmt.Errorf("lagoon: status %s: %w", pluginID, err)
	}
	applied := map[string]bool{}
	for _, id := range ids {
		applied[id] = true
	}
	ms := hm.Migrations()
	for i := len(ms) - 1; i >= 0; i-- {
		if ms[i] != nil && applied[ms[i].ID] {
			return ms[i].ID, nil
		}
	}
	return "", nil
}

// statusJSON is one migration of migrate:status --json.
type statusJSON struct {
	Plugin  string `json:"plugin"`
	Table   string `json:"table"`
	ID      string `json:"id"`
	Applied bool   `json:"applied"`
}

// RuntimeCommands returns migrate, migrate:rollback, migrate:status,
// deferred:purge and key:generate. Serve is registered separately via
// surf.ServeCommand.
func RuntimeCommands(app *backpack.App, plugins []party.Plugin) []bonfire.Command {
	return []bonfire.Command{
		{
			Name:        "migrate",
			Description: "Run plugin migrations in dependency order",
			Long: `Applies the pending migrations: the framework's own sets (uploads, backend
admin, deferred bindings, job queue) first, then each plugin's in dependency
order. Each plugin keeps its history in its own summer_migrations_<plugin>
table, so a migration runs once.

--pretend lists the pending migrations and applies nothing. In production, on
an interactive terminal, migrate asks before applying; --force skips the
question. Off a terminal (a deploy over SSH, a container entrypoint) it never
asks.`,
			Flags: []bonfire.Flag{pretendFlag, {Name: "force", Description: forceDescription, Bare: true}},
			Examples: []bonfire.Example{
				{Command: "migrate", Description: "Apply every pending migration"},
				{Command: "migrate --pretend", Description: "List the pending migrations without applying them"},
				{Command: "migrate --force", Description: "In production, apply without the confirmation question"},
			},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				return withDB(ctx, app, func(gdb *gorm.DB) error {
					pending, err := PendingMigrations(gdb, plugins)
					if err != nil {
						return err
					}
					if flagOn(in, "pretend") {
						for _, ref := range pending {
							out.Println(ref.Plugin + ": " + ref.ID)
						}
						out.Info(fmt.Sprintf("%d migrations would run", len(pending)))
						return nil
					}
					if len(pending) == 0 {
						out.Success("Nothing to migrate")
						return nil
					}
					if err := confirmProduction(app, in, out, fmt.Sprintf("Apply %d migrations to the production database?", len(pending)), "Migration cancelled."); err != nil {
						return err
					}
					if err := Migrate(gdb, plugins); err != nil {
						return err
					}
					counts := map[string]int{}
					var order []string
					for _, ref := range pending {
						if counts[ref.Plugin] == 0 {
							order = append(order, ref.Plugin)
						}
						counts[ref.Plugin]++
					}
					for _, plugin := range order {
						out.Info(fmt.Sprintf("%s: %d applied", plugin, counts[plugin]))
					}
					out.Success(fmt.Sprintf("Applied %d migrations", len(pending)))
					return nil
				})
			},
		},
		{
			Name:        "migrate:rollback",
			Description: "Roll back the last migration of a plugin",
			Long: `Rolls back the last applied migration of one plugin (--plugin), or of the
last plugin in activation order that has migrations. Run it again to roll
back further. --pretend names the migration that would roll back. In
production, on an interactive terminal, it asks first; --force skips the
question.`,
			Flags: []bonfire.Flag{{
				Name:        "plugin",
				Description: "Plugin ID whose last migration to roll back",
			}, pretendFlag, {Name: "force", Description: forceDescription, Bare: true}},
			Examples: []bonfire.Example{
				{Command: "migrate:rollback --plugin acme.blog", Description: "Roll back the last migration of acme.blog"},
				{Command: "migrate:rollback --plugin acme.blog --pretend", Description: "Name the migration that would roll back"},
			},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				plugin := ""
				if in != nil {
					plugin, _ = in.Flag("plugin")
				}
				plugin = strings.TrimSpace(plugin)
				if plugin == "" {
					plugin = lastMigrationPlugin(plugins)
				}
				if plugin == "" {
					return ErrNoMigrations
				}
				return withDB(ctx, app, func(gdb *gorm.DB) error {
					id, err := lastApplied(gdb, plugins, plugin)
					if err != nil {
						return err
					}
					if flagOn(in, "pretend") {
						if id == "" {
							out.Info(fmt.Sprintf("%s has no applied migration to roll back", plugin))
							return nil
						}
						out.Info(fmt.Sprintf("Would roll back %s of %s", id, plugin))
						return nil
					}
					if err := confirmProduction(app, in, out, fmt.Sprintf("Roll back %s of %s on the production database?", id, plugin), "Rollback cancelled."); err != nil {
						return err
					}
					if err := RollbackLast(gdb, plugins, plugin); err != nil {
						return err
					}
					if id == "" {
						out.Success(fmt.Sprintf("Rolled back the last migration of %s", plugin))
						return nil
					}
					out.Success(fmt.Sprintf("Rolled back %s of %s", id, plugin))
					return nil
				})
			},
		},
		{
			Name:        "migrate:status",
			Description: "Show per-plugin migration history",
			Long: `Lists each plugin with migrations, its history table and the migration IDs
applied. --json prints every declared migration of those plugins with its
table and whether it is applied, for scripts.`,
			Flags: []bonfire.Flag{jsonFlag},
			Examples: []bonfire.Example{
				{Command: "migrate:status", Description: "Show the applied migrations per plugin"},
				{Command: "migrate:status --json", Description: "Machine-readable status, pending migrations included"},
			},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				return withDB(ctx, app, func(gdb *gorm.DB) error {
					rows, err := Status(gdb, plugins)
					if err != nil {
						return err
					}
					if flagOn(in, "json") {
						pending, err := PendingMigrations(gdb, plugins)
						if err != nil {
							return err
						}
						list := []statusJSON{}
						for _, row := range rows {
							for _, id := range row.IDs {
								list = append(list, statusJSON{Plugin: row.Plugin, Table: row.Table, ID: id, Applied: true})
							}
							for _, ref := range pending {
								if ref.Plugin == row.Plugin {
									list = append(list, statusJSON{Plugin: row.Plugin, Table: row.Table, ID: ref.ID})
								}
							}
						}
						return printJSON(out, list)
					}
					tableRows := make([][]string, 0, len(rows))
					for _, row := range rows {
						ids := "(none)"
						if len(row.IDs) > 0 {
							ids = strings.Join(row.IDs, ", ")
						}
						tableRows = append(tableRows, []string{row.Plugin, row.Table, ids})
					}
					out.Table([]string{"plugin", "table", "applied"}, tableRows)
					return nil
				})
			},
		},
		{
			Name:        "deferred:purge",
			Description: "Delete expired deferred bindings with their pending uploads and created records",
			Long: `Deletes deferred bindings older than --days (default
database.deferred_bindings.purge_days, else 5): uploads attached to a form that
was never saved, with their files, and records created under deferral. Run it
daily from the scheduler or cron. --pretend counts the bindings that would be
purged and deletes nothing. In production, on an interactive terminal, it
asks first; --force skips the question.`,
			Flags: []bonfire.Flag{{
				Name:        "days",
				Description: "Purge bindings older than this many days",
			}, pretendFlag, {Name: "force", Description: forceDescription, Bare: true}},
			Examples: []bonfire.Example{
				{Command: "deferred:purge", Description: "Purge bindings older than the configured number of days"},
				{Command: "deferred:purge --days 2 --pretend", Description: "Count the bindings older than two days"},
			},
			Run: func(ctx context.Context, in bonfire.Input, out bonfire.Output) error {
				days, err := purgeDays(app, in)
				if err != nil {
					return err
				}
				before := time.Now().Add(-time.Duration(days) * 24 * time.Hour)
				return withDB(ctx, app, func(gdb *gorm.DB) error {
					if flagOn(in, "pretend") {
						var n int64
						if err := gdb.WithContext(ctx).Model(&DeferredBinding{}).Where("created_at < ?", before).Count(&n).Error; err != nil {
							return fmt.Errorf("lagoon: count deferred bindings: %w", err)
						}
						out.Info(fmt.Sprintf("%d deferred bindings older than %d days would be purged", n, days))
						return nil
					}
					if err := confirmProduction(app, in, out, fmt.Sprintf("Purge deferred bindings older than %d days from the production database?", days), "Purge cancelled."); err != nil {
						return err
					}
					models, err := deferredModels(gdb, plugins)
					if err != nil {
						return err
					}
					bucket, closeBucket, err := purgeBucket(ctx, app)
					if err != nil {
						return err
					}
					defer closeBucket()
					res, err := PurgeDeferred(ctx, gdb, bucket, PurgeOptions{
						Before: before,
						Models: func(slaveType string) (any, bool) {
							m, ok := models[slaveType]
							return m, ok
						},
					})
					if err != nil {
						return err
					}
					out.Success(fmt.Sprintf("purged %d deferred bindings older than %d days (%d files, %d children, %d skipped)",
						res.Bindings, days, res.Files, res.Children, res.Skipped))
					return nil
				})
			},
		},
		KeyGenerateCommand(),
	}
}

// printJSON writes v as indented JSON and a newline on out (data: printed
// under -q too).
func printJSON(out bonfire.Output, v any) error {
	b, err := json.MarshalIndent(v, "", "  ")
	if err != nil {
		return err
	}
	out.Println(string(b))
	return nil
}

// purgeDays is the --days flag, else database.deferred_bindings.purge_days,
// else WinterCMS's five days. A negative or non-integer value is an error.
func purgeDays(app *backpack.App, in bonfire.Input) (int, error) {
	if in != nil {
		if raw, ok := in.Flag("days"); ok {
			n, err := strconv.Atoi(strings.TrimSpace(raw))
			if err != nil || n < 0 {
				return 0, fmt.Errorf("lagoon: deferred:purge --days %q must be a whole number of days, 0 or more", raw)
			}
			return n, nil
		}
	}
	if app == nil || app.Config == nil {
		return defaultPurgeDays, nil
	}
	raw, ok := app.Config.Lookup(purgeDaysKey)
	if !ok || raw == nil {
		return defaultPurgeDays, nil
	}
	var n int
	switch v := raw.(type) {
	case int:
		n = v
	case int64:
		n = int(v)
	case uint64:
		n = int(v)
	case float64:
		if v != float64(int(v)) {
			return 0, fmt.Errorf("lagoon: %s %v must be a whole number of days", purgeDaysKey, raw)
		}
		n = int(v)
	case string:
		parsed, err := strconv.Atoi(strings.TrimSpace(v))
		if err != nil {
			return 0, fmt.Errorf("lagoon: %s %q must be a whole number of days", purgeDaysKey, v)
		}
		n = parsed
	default:
		return 0, fmt.Errorf("lagoon: %s %v must be a whole number of days", purgeDaysKey, raw)
	}
	if n < 0 {
		return 0, fmt.Errorf("lagoon: %s %d must not be negative", purgeDaysKey, n)
	}
	return n, nil
}

// deferredModels maps the MorphType of every plugin model to the model, so
// the purge can delete records created under deferral. Two different model
// types with the same morph type are an error.
func deferredModels(gdb *gorm.DB, plugins []party.Plugin) (map[string]any, error) {
	out := map[string]any{}
	for _, p := range plugins {
		hm, ok := p.(pact.HasModels)
		if !ok {
			continue
		}
		for _, m := range hm.Models() {
			if m == nil {
				continue
			}
			key, err := MorphType(gdb, m)
			if err != nil {
				return nil, fmt.Errorf("lagoon: deferred:purge: plugin %s: %w", p.ID(), err)
			}
			if prev, dup := out[key]; dup {
				if modelType(prev) != modelType(m) {
					return nil, fmt.Errorf("lagoon: deferred:purge: models %s and %s share the morph type %q", modelType(prev), modelType(m), key)
				}
				continue
			}
			out[key] = m
		}
	}
	return out, nil
}

func modelType(m any) reflect.Type {
	t := reflect.TypeOf(m)
	for t != nil && t.Kind() == reflect.Pointer {
		t = t.Elem()
	}
	return t
}

// purgeBucket is the published uploads bucket, else one opened from
// storage.uploads.bucket_url and closed by the returned func. Without a
// configured bucket it returns nil; PurgeDeferred then refuses only when an
// expired binding points at a file.
func purgeBucket(ctx context.Context, app *backpack.App) (*blob.Bucket, func(), error) {
	noop := func() {}
	if app == nil {
		return nil, noop, nil
	}
	if b, ok := app.Lookup[*blob.Bucket](); ok && b != nil {
		return b, noop, nil
	}
	if app.Config == nil || strings.TrimSpace(app.Config.String("storage.uploads.bucket_url")) == "" {
		return nil, noop, nil
	}
	b, err := attach.OpenBucket(ctx, app.Config)
	if err != nil {
		return nil, noop, err
	}
	return b, func() { _ = b.Close() }, nil
}

func withDB(ctx context.Context, app *backpack.App, fn func(*gorm.DB) error) error {
	sqlDB, gdb, err := OpenFromApp(ctx, app)
	if err != nil {
		return err
	}
	defer sqlDB.Close()
	if err := Publish(app, sqlDB, gdb); err != nil {
		return err
	}
	return fn(gdb)
}