package cmd

import (
	"fmt"
	"io"
	"os"
	"strings"

	"github.com/spf13/cobra"
	"github.com/warkanum/unitdore/config"
	"github.com/warkanum/unitdore/runtime"
	"github.com/warkanum/unitdore/systemd"
	"github.com/warkanum/unitdore/sysuser"
)

var syncupCmd = &cobra.Command{
	Use:   "syncup",
	Short: "Discover running containers and sync them into the config",
	Long: `Syncup queries all available runtimes for running containers and adds
any new ones to the config file. Existing entries are never removed.

Podman is queried first. Docker is only a fallback: a container name found
in podman is never registered as docker.

Containers created by podman-compose are grouped into one stack unit per
project. Existing per-container units of stack members are disabled.

Scopes: as root, root's containers plus rootless containers of each user in
'users:' (podman only). As a normal user, the user's own podman containers.

It also reconciles: if a configured unit's container or stack no longer
exists, it is marked disabled with a reason.`,
	RunE: runSyncup,
}

func init() {
	rootCmd.AddCommand(syncupCmd)
}

const (
	reasonNotFound      = "container not found"
	reasonStackNotFound = "stack not found"
	reasonMemberPrefix  = "part of stack "
)

type syncStats struct {
	added, unchanged, disabled, reenabled int
}

func runSyncup(cmd *cobra.Command, args []string) error {
	cfg, err := config.LoadOrEmpty(configPath)
	if err != nil {
		return err
	}

	containers := discover(syncScopes(cfg))

	var st syncStats
	running := mergeDiscovered(cfg, containers, composeBinFor, os.Stdout, &st)
	reconcile(cfg, running, unitExists, os.Stdout, &st)

	if err := cfg.Save(configPath); err != nil {
		return err
	}

	fmt.Printf("\nDone. Added: %d  Unchanged: %d  Disabled: %d  Re-enabled: %d\n", st.added, st.unchanged, st.disabled, st.reenabled)
	return nil
}

// syncScopes returns the user scopes to scan ("" = root/system).
func syncScopes(cfg *config.Config) []string {
	if sysuser.IsRoot() {
		return append([]string{""}, cfg.Users...)
	}
	return []string{sysuser.Current()}
}

// discover lists running containers in every scope, podman first.
func discover(scopes []string) []runtime.Container {
	var all []runtime.Container
	for _, user := range scopes {
		for _, rt := range runtime.Available() {
			// Docker is a system daemon; user scopes only see rootless podman
			if user != "" && rt.Name() == "docker" {
				continue
			}
			containers, err := rt.ListRunning(user)
			if err != nil {
				fmt.Fprintf(os.Stderr, "warning: %s discovery failed (%s): %v\n", rt.Name(), scopeName(user), err)
				continue
			}
			all = append(all, containers...)
		}
	}
	return all
}

func composeBinFor(user string) string {
	return sysuser.LookPath(user, "podman-compose")
}

func scopeName(user string) string {
	if user == "" {
		return "root"
	}
	return user
}

func scopeKey(user, name string) string { return user + "/" + name }

// mergeDiscovered adds discovered containers and stacks to cfg. Returns the
// set of running scopeKey(user, name) for containers and stack projects.
func mergeDiscovered(cfg *config.Config, containers []runtime.Container, composeBin func(user string) string, w io.Writer, st *syncStats) map[string]bool {
	running := map[string]bool{}
	podmanNames := map[string]bool{}
	members := map[string]string{} // scopeKey(user, container) -> project

	for _, c := range containers {
		if c.Runtime == "podman" {
			podmanNames[scopeKey(c.User, c.Name)] = true
		}
	}

	// Group podman-compose containers into one stack unit per (user, project)
	for _, c := range containers {
		project := c.Project()
		if c.Runtime != "podman" || project == "" {
			continue
		}
		members[scopeKey(c.User, c.Name)] = project
		key := scopeKey(c.User, project)
		if running[key] {
			continue
		}
		running[key] = true

		stack := config.Unit{
			Name:         project,
			Runtime:      "podman",
			User:         c.User,
			Kind:         config.KindStack,
			Project:      project,
			WorkingDir:   c.WorkingDir(),
			ComposeFiles: c.ComposeFiles(),
			ComposeBin:   composeBin(c.User),
			Order:        len(cfg.Units) + 1,
			Enabled:      true,
		}
		existing := cfg.FindUnit(project)
		switch {
		case existing == nil:
			cfg.AddUnit(stack)
			fmt.Fprintf(w, "  + added stack: %s (%s, %s)\n", project, scopeName(c.User), strings.Join(stack.ComposeFiles, ","))
			st.added++
		case existing.IsStack() && existing.Project == project && existing.User == c.User:
			// Labels are the source of truth for where the stack lives
			existing.WorkingDir = stack.WorkingDir
			existing.ComposeFiles = stack.ComposeFiles
			if stack.ComposeBin != "" {
				existing.ComposeBin = stack.ComposeBin
			}
			st.unchanged++
		default:
			fmt.Fprintf(os.Stderr, "warning: stack %s (%s) skipped: unit name already used\n", project, scopeName(c.User))
		}
	}

	for _, c := range containers {
		key := scopeKey(c.User, c.Name)
		// Podman is queried first and wins on name clash (e.g. podman-docker shim)
		if c.Runtime != "podman" && podmanNames[key] {
			continue
		}
		running[key] = true
		if _, ok := members[key]; ok {
			continue
		}
		unit := config.Unit{
			Name:    c.Name,
			Runtime: c.Runtime,
			User:    c.User,
			Order:   len(cfg.Units) + 1,
			Enabled: true,
		}
		if cfg.AddUnit(unit) {
			fmt.Fprintf(w, "  + added: %s (%s, %s)\n", c.Name, c.Runtime, scopeName(c.User))
			st.added++
			continue
		}
		if existing := cfg.FindUnit(c.Name); existing.User != c.User {
			fmt.Fprintf(os.Stderr, "warning: %s (%s) skipped: unit name already used by %s\n", c.Name, scopeName(c.User), scopeName(existing.User))
			continue
		}
		st.unchanged++
	}

	for i := range cfg.Units {
		u := &cfg.Units[i]
		if u.IsStack() {
			continue
		}
		key := scopeKey(u.User, u.Name)
		if u.Runtime == "docker" && podmanNames[key] {
			u.Runtime = "podman"
			fmt.Fprintf(w, "  ~ runtime: %s docker -> podman\n", u.Name)
		}
		if project, ok := members[key]; ok && u.DisabledReason != reasonMemberPrefix+project {
			wasEnabled := u.Enabled
			u.Enabled = false
			u.DisabledReason = reasonMemberPrefix + project
			if wasEnabled {
				fmt.Fprintf(w, "  ! disabled: %s (%s)\n", u.Name, u.DisabledReason)
				st.disabled++
			}
		}
	}

	return running
}

// unitExists checks whether a unit's container or stack still exists.
func unitExists(u config.Unit) (bool, error) {
	if u.IsStack() {
		if systemd.ComposeAvailable(u) {
			return true, nil
		}
		return (&runtime.Podman{}).PodExists(u.User, runtime.PodName(u.Project))
	}
	rt := runtime.Get(u.Runtime)
	if rt == nil {
		return true, nil // unknown runtime — leave alone
	}
	return rt.Exists(u.User, u.Name)
}

// reconcile disables units whose container/stack is gone and re-enables
// units that were auto-disabled once it is back.
func reconcile(cfg *config.Config, running map[string]bool, exists func(config.Unit) (bool, error), w io.Writer, st *syncStats) {
	for i := range cfg.Units {
		u := &cfg.Units[i]
		if strings.HasPrefix(u.DisabledReason, reasonMemberPrefix) {
			continue
		}
		reason := reasonNotFound
		if u.IsStack() {
			reason = reasonStackNotFound
		}

		found := running[scopeKey(u.User, u.Name)]
		if !found {
			var err error
			found, err = exists(*u)
			if err != nil {
				fmt.Fprintf(os.Stderr, "warning: checking %s: %v\n", u.Name, err)
				continue
			}
		}

		if !found && u.Enabled {
			u.Enabled = false
			u.DisabledReason = reason
			fmt.Fprintf(w, "  ! disabled: %s (%s)\n", u.Name, reason)
			st.disabled++
		} else if found && !u.Enabled && u.DisabledReason == reason {
			u.Enabled = true
			u.DisabledReason = ""
			fmt.Fprintf(w, "  ✓ re-enabled: %s (found)\n", u.Name)
			st.reenabled++
		}
	}
}