package incus

// Nightly exports: every instance as a tarball in virt/exports/<name>/, kept to a count, as a
// cron line like the ZFS schedules — `hamlab virt-export` in /etc/cron.d/hamlab-virt — so the
// backup runs whether or not the console is up. The settings and the last run's record are
// files beside the data, not state.json, because the cron job is a separate process.

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

const CronFile = "/etc/cron.d/hamlab-virt"

type ExportConfig struct {
	Enabled      bool      `json:"enabled"`
	Hour         int       `json:"hour"`
	Minute       int       `json:"minute"`
	Keep         int       `json:"keep"`                // newest exports kept per instance
	InstanceOnly bool      `json:"instance_only"`       // leave the snapshots out of the tarball
	Instances    []string  `json:"instances,omitempty"` // empty: every instance
	Updated      time.Time `json:"updated,omitempty"`
}

func DefaultExportConfig() ExportConfig {
	return ExportConfig{Hour: 2, Minute: 15, Keep: 3, InstanceOnly: true}
}

func (c ExportConfig) Validate() error {
	if c.Hour < 0 || c.Hour > 23 || c.Minute < 0 || c.Minute > 59 {
		return errors.New("time: hour 0–23, minute 0–59")
	}
	if c.Keep < 1 || c.Keep > 100 {
		return errors.New("keep: between 1 and 100")
	}
	for _, n := range c.Instances {
		if !ValidName(n) {
			return errors.New("instance: " + n)
		}
	}
	return nil
}

func (c ExportConfig) CronExpr() string { return fmt.Sprintf("%d %d * * *", c.Minute, c.Hour) }

// NextRun is the next time the line fires, for the page.
func (c ExportConfig) NextRun(now time.Time) time.Time {
	n := time.Date(now.Year(), now.Month(), now.Day(), c.Hour, c.Minute, 0, 0, now.Location())
	if !n.After(now) {
		n = n.Add(24 * time.Hour)
	}
	return n
}

// CronText is the whole file; rewritten on every change, never edited.
func (c ExportConfig) CronText(user, exe, config string) string {
	var b strings.Builder
	b.WriteString("# Ham Lab instance exports — written by the Virtualization tab, rewritten whole on every change.\n")
	b.WriteString("# Edit it there, not here.\n")
	b.WriteString("SHELL=/bin/sh\nPATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\n\n")
	fmt.Fprintf(&b, "# every instance to virt/exports, keep %d each\n", c.Keep)
	fmt.Fprintf(&b, "%s %s %s -config %s virt-export\n", c.CronExpr(), user, exe, config)
	return b.String()
}

func (m *Manager) exportConfigPath() string { return filepath.Join(m.dir, "exports.json") }
func (m *Manager) exportRunPath() string    { return filepath.Join(m.dir, "export-runs.json") }

func (m *Manager) ExportConfig() ExportConfig {
	c := DefaultExportConfig()
	if b, err := os.ReadFile(m.exportConfigPath()); err == nil {
		_ = json.Unmarshal(b, &c)
	}
	return c
}

func (m *Manager) SaveExportConfig(c ExportConfig) error {
	if err := c.Validate(); err != nil {
		return err
	}
	if err := m.EnsureDirs(); err != nil {
		return err
	}
	c.Updated = time.Now()
	b, _ := json.MarshalIndent(c, "", "  ")
	return os.WriteFile(m.exportConfigPath(), b, 0o644)
}

type ExportRun struct {
	At       time.Time `json:"at"`
	Exported []string  `json:"exported"`
	Pruned   []string  `json:"pruned"`
	Errors   []string  `json:"errors,omitempty"`
	Seconds  float64   `json:"seconds"`
}

func (m *Manager) LastExportRun() *ExportRun {
	b, err := os.ReadFile(m.exportRunPath())
	if err != nil {
		return nil
	}
	var r ExportRun
	if json.Unmarshal(b, &r) != nil {
		return nil
	}
	return &r
}

// ExportFile is one tarball in the exports tree.
type ExportFile struct {
	Instance string    `json:"instance"`
	Name     string    `json:"name"`
	Size     int64     `json:"size"`
	Modified time.Time `json:"modified"`
}

func (m *Manager) ExportFiles() []ExportFile {
	out := []ExportFile{}
	dirs, _ := os.ReadDir(m.ExportsDir())
	for _, d := range dirs {
		if !d.IsDir() {
			continue
		}
		files, _ := os.ReadDir(filepath.Join(m.ExportsDir(), d.Name()))
		for _, f := range files {
			if f.IsDir() || strings.HasSuffix(f.Name(), ".part") {
				continue
			}
			if info, err := f.Info(); err == nil {
				out = append(out, ExportFile{Instance: d.Name(), Name: f.Name(), Size: info.Size(), Modified: info.ModTime()})
			}
		}
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Instance != out[j].Instance {
			return out[i].Instance < out[j].Instance
		}
		return out[i].Modified.After(out[j].Modified)
	})
	return out
}

// RunExports exports the named instances (or every one when names is empty) and prunes each
// instance's folder to the configured count. Output goes to w line by line for a task to show.
func (m *Manager) RunExports(ctx context.Context, names []string, w func(string)) ExportRun {
	start := time.Now()
	c := m.ExportConfig()
	run := ExportRun{At: start, Exported: []string{}, Pruned: []string{}}
	if err := m.EnsureDirs(); err != nil {
		run.Errors = append(run.Errors, err.Error())
		return run
	}
	all, err := m.Instances(ctx)
	if err != nil {
		run.Errors = append(run.Errors, "listing instances: "+err.Error())
		return run
	}
	want := map[string]bool{}
	for _, n := range names {
		want[n] = true
	}
	if len(names) == 0 && len(c.Instances) > 0 {
		for _, n := range c.Instances {
			want[n] = true
		}
	}
	for _, in := range all {
		if len(want) > 0 && !want[in.Name] {
			continue
		}
		dir := filepath.Join(m.ExportsDir(), in.Name)
		if err := os.MkdirAll(dir, 0o755); err != nil {
			run.Errors = append(run.Errors, in.Name+": "+err.Error())
			continue
		}
		stamp := start.Format("2006-01-02_15.04")
		final := filepath.Join(dir, fmt.Sprintf("%s-%s.tar.gz", in.Name, stamp))
		part := final + ".part"
		args := []string{"export", in.Name, part}
		if c.InstanceOnly {
			args = append(args, "--instance-only")
		}
		w(fmt.Sprintf("exporting %s …", in.Name))
		cctx, cancel := context.WithTimeout(ctx, 2*time.Hour)
		out, err := exec.CommandContext(cctx, "incus", args...).CombinedOutput()
		cancel()
		if err != nil {
			_ = os.Remove(part)
			msg := strings.TrimSpace(string(out))
			if msg == "" {
				msg = err.Error()
			}
			run.Errors = append(run.Errors, in.Name+": "+msg)
			w("  failed: " + msg)
			continue
		}
		if err := os.Rename(part, final); err != nil {
			run.Errors = append(run.Errors, in.Name+": "+err.Error())
			continue
		}
		if st, err := os.Stat(final); err == nil {
			w(fmt.Sprintf("  %s (%.1f MiB)", filepath.Base(final), float64(st.Size())/(1<<20)))
		}
		run.Exported = append(run.Exported, filepath.Base(final))
		// prune: newest first, keep c.Keep
		var files []ExportFile
		for _, f := range m.ExportFiles() {
			if f.Instance == in.Name {
				files = append(files, f)
			}
		}
		for i := c.Keep; i < len(files); i++ {
			if err := os.Remove(filepath.Join(dir, files[i].Name)); err == nil {
				run.Pruned = append(run.Pruned, files[i].Name)
				w("  pruned " + files[i].Name)
			}
		}
	}
	run.Seconds = time.Since(start).Seconds()
	b, _ := json.MarshalIndent(run, "", "  ")
	_ = os.WriteFile(m.exportRunPath(), b, 0o644)
	return run
}