package migrate

import (
	"fmt"
	"io"
	"sort"
	"strings"
	"time"

	adminmodels "go-admin/app/admin/models"
	"go-admin/cmd/migrate/migration"
)

const applyTimeLayout = "2006-01-02 15:04:05"

// printStatus lists every migration this binary knows about together with every
// row already in sys_migration, grouped by app.
//
// apps is what sys_app says about each of them, keyed by app code, and it
// answers a different question from the migration rows: an install that
// stopped partway leaves migrations that all read "applied" and a row that
// says the install never finished. A nil map is a database from before
// sys_app existed, and the listing is then exactly what it was.
//
// The app list is the union of the two. Reading it from sys_app alone would
// drop an application whose migrations ran under plain `migrate` and which
// therefore has no row; reading it from the migration rows alone drops one
// whose code has been taken out of the binary, which is when somebody most
// wants to see it named.
//
// filter is an app code as typed on the command line; empty means every app.
func printStatus(w io.Writer, entries []migration.StatusEntry, apps map[string]adminmodels.SysApp, filter string) error {
	entries = filterByApp(entries, filter)
	apps = filterAppsByApp(apps, filter)

	groups, order := groupByApp(entries, apps)
	if len(order) == 0 {
		_, err := fmt.Fprintln(w, "no migrations registered and none recorded")
		return err
	}

	// One width for the whole listing rather than one per group: the versions
	// of two apps line up, so a long list can be read down the column.
	width := versionWidth(entries)

	var applied, pending, orphaned int
	for i, app := range order {
		if i > 0 {
			fmt.Fprintln(w)
		}
		fmt.Fprintf(w, "[%s]%s\n", app, appSummary(apps, app))
		if len(groups[app]) == 0 {
			// A row in sys_app and not one migration, recorded or
			// registered. Its code is out of this binary and its migration
			// records have been removed, and the row is all that is left to
			// say it was ever here.
			fmt.Fprintln(w, "  no migrations registered in this binary and none recorded")
		}
		for _, e := range groups[app] {
			state := "pending"
			switch {
			case e.Applied && !e.Registered:
				state = "orphaned"
				orphaned++
			case e.Applied:
				state = "applied"
				applied++
			default:
				pending++
			}
			fmt.Fprintln(w, strings.TrimRight(
				fmt.Sprintf("  %-*s%-*s%s", stateWidth, state, width, e.Version, formatApplyTime(e.ApplyTime)), " "))
		}
	}

	fmt.Fprintf(w, "\n%d applied, %d pending across %d app(s)\n", applied, pending, len(order))
	if orphaned > 0 {
		fmt.Fprintf(w, "%d orphaned: recorded in sys_migration, but nothing in this binary registers them.\n"+
			"Expected after a migration file is removed or an app is uninstalled; they will not run again.\n", orphaned)
	}
	return nil
}

// printPending is --dry-run: the same data as status, narrowed to what an
// actual run would do and printed in the order it would do it.
//
// It reads and prints. Every write path - AutoMigrate on sys_migration
// included - is on the other branch in initDB, so a dry run leaves the database
// byte for byte as it found it.
func printPending(w io.Writer, entries []migration.StatusEntry, filter string) error {
	entries = filterByApp(entries, filter)

	fmt.Fprintln(w, "dry-run: nothing will be written")

	pending := make([]migration.StatusEntry, 0, len(entries))
	for _, e := range entries {
		// An orphaned row is recorded and unregistered; a real run cannot
		// apply it, so a dry run must not offer to.
		if !e.Applied && e.Registered {
			pending = append(pending, e)
		}
	}
	if len(pending) == 0 {
		_, err := fmt.Fprintln(w, "nothing to apply")
		return err
	}

	appWidth := 0
	for _, e := range pending {
		if n := len(migration.DisplayAppCode(e.AppCode)) + 2; n > appWidth {
			appWidth = n
		}
	}

	fmt.Fprintln(w, "would apply, in this order:")
	for _, e := range pending {
		fmt.Fprintf(w, "  %-*s%s\n", appWidth+2, "["+migration.DisplayAppCode(e.AppCode)+"]", e.Version)
	}
	fmt.Fprintf(w, "\n%d migration(s) pending\n", len(pending))
	return nil
}

// stateWidth is the width of the applied/pending/orphaned column, sized to the
// longest of the three plus a gap.
const stateWidth = len("orphaned") + 2

func versionWidth(entries []migration.StatusEntry) int {
	width := 0
	for _, e := range entries {
		if n := len(e.Version) + 2; n > width {
			width = n
		}
	}
	return width
}

// filterByApp keeps the entries of one app. The filter is matched after the
// same normalisation ForApp applies, so --app CRM finds crm.
func filterByApp(entries []migration.StatusEntry, filter string) []migration.StatusEntry {
	if filter == "" {
		return entries
	}
	want := migration.AppFilter(filter)
	out := make([]migration.StatusEntry, 0, len(entries))
	for _, e := range entries {
		if e.AppCode == want {
			out = append(out, e)
		}
	}
	return out
}

// groupByApp buckets entries by display name and returns the buckets plus the
// order to print them in: the framework first, then apps alphabetically. That
// is also the order a full run executes them in, because version strings sort
// as ASCII and the framework's are bare digits.
func groupByApp(entries []migration.StatusEntry, apps map[string]adminmodels.SysApp) (map[string][]migration.StatusEntry, []string) {
	groups := make(map[string][]migration.StatusEntry)
	for _, e := range entries {
		app := migration.DisplayAppCode(e.AppCode)
		groups[app] = append(groups[app], e)
	}
	// An application sys_app knows about and no migration mentions still gets
	// a group, empty. That is the one case the migration rows cannot report
	// at all.
	for code := range apps {
		app := migration.DisplayAppCode(code)
		if _, ok := groups[app]; !ok {
			groups[app] = nil
		}
	}
	order := make([]string, 0, len(groups))
	for app := range groups {
		order = append(order, app)
	}
	sort.Slice(order, func(i, j int) bool {
		if (order[i] == migration.FrameworkAppCode) != (order[j] == migration.FrameworkAppCode) {
			return order[i] == migration.FrameworkAppCode
		}
		return order[i] < order[j]
	})
	return groups, order
}

// appSummary is what sys_app says about one application, as a suffix for its
// group header. Empty when there is no row: an application whose migrations
// ran under plain `migrate` has none, and neither does any application on a
// database from before sys_app existed.
func appSummary(apps map[string]adminmodels.SysApp, display string) string {
	// AppFilter, not NormalizeAppCode: this takes a display code back to the
	// stored one, and only AppFilter is that inverse. It maps the framework
	// to the empty string, which loadApps never files a row under, so the
	// framework needs no branch of its own here.
	row, ok := apps[migration.AppFilter(display)]
	if !ok {
		return ""
	}
	switch row.Status {
	case adminmodels.AppInstalled:
		return fmt.Sprintf("  %s installed", row.Version)
	case adminmodels.AppFailed:
		if row.FailedVersion != "" {
			return fmt.Sprintf("  %s failed at %s", row.Version, row.FailedVersion)
		}
		return fmt.Sprintf("  %s failed", row.Version)
	case adminmodels.AppInstalling:
		// Not "installing" as in "right now": nothing holds this state while
		// it works. It is what is left when an attempt did not reach either
		// end, and running the install again is what clears it.
		return fmt.Sprintf("  %s did not finish installing", row.Version)
	default:
		return fmt.Sprintf("  %s status %d", row.Version, row.Status)
	}
}

// filterAppsByApp narrows the sys_app rows the same way filterByApp narrows
// the migrations, so --app names one application in both halves of the report.
func filterAppsByApp(apps map[string]adminmodels.SysApp, filter string) map[string]adminmodels.SysApp {
	if filter == "" {
		return apps
	}
	want := migration.AppFilter(filter)
	out := make(map[string]adminmodels.SysApp, 1)
	if row, ok := apps[want]; ok {
		out[want] = row
	}
	return out
}

func formatApplyTime(t *time.Time) string {
	if t == nil {
		return ""
	}
	return t.Format(applyTimeLayout)
}