package subsystems

import (
	"context"
	"flag"
	"fmt"
	"strings"

	"github.com/safing/portbase/database"
	_ "github.com/safing/portbase/database/dbmodule" // database module is required
	"github.com/safing/portbase/modules"
)

const (
	configChangeEvent      = "config change"
	subsystemsStatusChange = "status change"
)

var (
	module         *modules.Module
	printGraphFlag bool

	databaseKeySpace string
	db               = database.NewInterface(nil)
)

func init() {
	// enable partial starting
	modules.EnableModuleManagement(handleModuleChanges)

	// register module and enable it for starting
	module = modules.Register("subsystems", prep, start, nil, "config", "database")
	module.Enable()

	// register event for changes in the subsystem
	module.RegisterEvent(subsystemsStatusChange)

	flag.BoolVar(&printGraphFlag, "print-subsystem-graph", false, "print the subsystem module dependency graph")
}

func prep() error {
	if printGraphFlag {
		printGraph()
		return modules.ErrCleanExit
	}

	return module.RegisterEventHook("config", configChangeEvent, "control subsystems", handleConfigChanges)
}

func start() error {
	// lock registration
	subsystemsLocked.Set()

	// lock slice and map
	subsystemsLock.Lock()
	// go through all dependencies
	seen := make(map[string]struct{})
	for _, sub := range subsystems {
		// add main module
		sub.Dependencies = append(sub.Dependencies, statusFromModule(sub.module))
		// add dependencies
		sub.addDependencies(sub.module, seen)
	}
	// unlock
	subsystemsLock.Unlock()

	// apply config
	module.StartWorker("initial subsystem configuration", func(ctx context.Context) error {
		return handleConfigChanges(module.Ctx, nil)
	})
	return nil
}

func (sub *Subsystem) addDependencies(module *modules.Module, seen map[string]struct{}) {
	for _, module := range module.Dependencies() {
		_, ok := seen[module.Name]
		if !ok {
			// add dependency to modules
			sub.Dependencies = append(sub.Dependencies, statusFromModule(module))
			// mark as seen
			seen[module.Name] = struct{}{}
			// add further dependencies
			sub.addDependencies(module, seen)
		}
	}
}

// SetDatabaseKeySpace sets a key space where subsystem status
func SetDatabaseKeySpace(keySpace string) {
	if databaseKeySpace == "" {
		databaseKeySpace = keySpace

		if !strings.HasSuffix(databaseKeySpace, "/") {
			databaseKeySpace += "/"
		}
	}
}

func printGraph() {
	// mark roots
	for _, sub := range subsystems {
		sub.module.Enable() // mark as tree root
	}
	// print
	for _, sub := range subsystems {
		printModuleGraph("", sub.module, true)
	}
}

func printModuleGraph(prefix string, module *modules.Module, root bool) {
	fmt.Printf("%s├── %s\n", prefix, module.Name)
	if root || !module.Enabled() {
		for _, dep := range module.Dependencies() {
			printModuleGraph(fmt.Sprintf("│   %s", prefix), dep, false)
		}
	}
}