// SPDX-License-Identifier: EUPL-1.2

// Package core is a dependency injection and service lifecycle framework for Go.
// This file defines the Core struct, accessors, and IPC/error wrappers.

package core

import (
	"context"
	"os"
	"sync"
	"sync/atomic"
)

// --- Core Struct ---

// Core is the central application object that manages services, assets, and communication.
type Core struct {
	options *Options    // c.Options()        — Input configuration used to create this Core
	app     *App        // c.App()            — Application identity + optional GUI runtime
	data    *Data       // c.Data()           — Embedded/stored content from packages
	drive   *Drive      // c.Drive()          — Resource handle registry (transports)
	fs      *Fs         // c.Fs()             — Local filesystem I/O (sandboxable)
	config  *Config     // c.Config()         — Configuration, settings, feature flags
	error   *ErrorPanic // c.Error()          — Panic recovery and crash reporting
	log     *ErrorLog   // c.Log()            — Structured logging + error wrapping
	// cli accessed via ServiceFor[*Cli](c, "cli")
	commands *CommandRegistry // c.Command("path")  — Command tree
	services *ServiceRegistry // c.Service("name")  — Service registry
	lock     *Lock            // c.Lock("name")     — Named mutexes
	ipc      *Ipc             // c.IPC()            — Message bus for IPC
	api      *API             // c.API()            — Remote streams
	info     *SysInfo         // c.Env("key")        — Read-only system/environment information
	i18n     *I18n            // c.I18n()           — Internationalisation and locale collection

	entitlementChecker EntitlementChecker // default: everything permitted
	usageRecorder      UsageRecorder      // default: nil (no-op)

	context       context.Context
	cancel        context.CancelFunc
	taskIDCounter atomic.Uint64
	waitGroup     sync.WaitGroup
	shutdown      atomic.Bool
}

// --- Accessors ---

// Options returns the input configuration passed to core.New().
//
//	opts := c.Options()
//	name := opts.String("name")
func (c *Core) Options() *Options { return c.options }

// App returns application identity metadata.
//
//	c.App().Name     // "my-app"
//	c.App().Version  // "1.0.0"
func (c *Core) App() *App { return c.app }

// Data returns the embedded asset registry (Registry[*Embed]).
//
//	r := c.Data().ReadString("prompts/coding.md")
func (c *Core) Data() *Data { return c.data }

// Drive returns the transport handle registry (Registry[*DriveHandle]).
//
//	r := c.Drive().Get("forge")
func (c *Core) Drive() *Drive { return c.drive }

// Fs returns the sandboxed filesystem.
//
//	r := c.Fs().Read("/path/to/file")
//	c.Fs().WriteAtomic("/status.json", data)
func (c *Core) Fs() *Fs { return c.fs }

// Config returns runtime settings and feature flags.
//
//	host := c.Config().String("database.host")
//	c.Config().Enable("dark-mode")
func (c *Core) Config() *Config { return c.config }

// Error returns the panic recovery subsystem.
//
//	c.Error().Recover()
func (c *Core) Error() *ErrorPanic { return c.error }

// Log returns the structured logging subsystem.
//
//	c.Log().Info("started", "port", 8080)
func (c *Core) Log() *ErrorLog { return c.log }

// Cli returns the CLI command framework (registered as service "cli").
//
//	c.Cli().Run("deploy", "to", "homelab")
func (c *Core) Cli() *Cli {
	cl, _ := ServiceFor[*Cli](c, "cli")
	return cl
}

// IPC returns the message bus internals.
//
//	c.IPC()
func (c *Core) IPC() *Ipc { return c.ipc }

// I18n returns the internationalisation subsystem.
//
//	tr := c.I18n().Translate("cmd.deploy.description")
func (c *Core) I18n() *I18n { return c.i18n }

// Env returns an environment variable by key (cached at init, falls back to os.Getenv).
//
//	home := c.Env("DIR_HOME")
//	token := c.Env("FORGE_TOKEN")
func (c *Core) Env(key string) string { return Env(key) }

// Context returns Core's lifecycle context (cancelled on shutdown).
//
//	ctx := c.Context()
func (c *Core) Context() context.Context { return c.context }

// Core returns self — satisfies the ServiceRuntime interface.
//
//	c := s.Core()
func (c *Core) Core() *Core { return c }

// --- Lifecycle ---

// RunE starts all services, runs the CLI, then shuts down.
// Returns an error instead of calling os.Exit — let main() handle the exit.
// ServiceShutdown is always called via defer, even on startup failure or panic.
//
//	if err := c.RunE(); err != nil {
//	    os.Exit(1)
//	}
func (c *Core) RunE() error {
	defer c.ServiceShutdown(context.Background())

	r := c.ServiceStartup(c.context, nil)
	if !r.OK {
		if err, ok := r.Value.(error); ok {
			return err
		}
		return E("core.Run", "startup failed", nil)
	}

	if cli := c.Cli(); cli != nil {
		r = cli.Run()
	}

	if !r.OK {
		if err, ok := r.Value.(error); ok {
			return err
		}
	}
	return nil
}

// Run starts all services, runs the CLI, then shuts down.
// Calls os.Exit(1) on failure. For error handling use RunE().
//
//	c := core.New(core.WithService(myService.Register))
//	c.Run()
func (c *Core) Run() {
	if err := c.RunE(); err != nil {
		Error(err.Error())
		os.Exit(1)
	}
}

// --- IPC (uppercase aliases) ---

// ACTION broadcasts a message to all registered handlers (fire-and-forget).
// Each handler is wrapped in panic recovery. All handlers fire regardless.
//
//	c.ACTION(messages.AgentCompleted{Agent: "codex", Status: "completed"})
func (c *Core) ACTION(msg Message) Result { return c.broadcast(msg) }

// QUERY sends a request — first handler to return OK wins.
//
//	r := c.QUERY(MyQuery{Name: "brain"})
func (c *Core) QUERY(q Query) Result { return c.Query(q) }

// QUERYALL sends a request — collects all OK responses.
//
//	r := c.QUERYALL(countQuery{})
//	results := r.Value.([]any)
func (c *Core) QUERYALL(q Query) Result { return c.QueryAll(q) }

// --- Error+Log ---

// LogError logs an error and returns the Result from ErrorLog.
func (c *Core) LogError(err error, op, msg string) Result {
	return c.log.Error(err, op, msg)
}

// LogWarn logs a warning and returns the Result from ErrorLog.
func (c *Core) LogWarn(err error, op, msg string) Result {
	return c.log.Warn(err, op, msg)
}

// Must logs and panics if err is not nil.
func (c *Core) Must(err error, op, msg string) {
	c.log.Must(err, op, msg)
}

// --- Registry Accessor ---

// RegistryOf returns a named registry for cross-cutting queries.
// Known registries: "services", "commands", "actions".
//
//	c.RegistryOf("services").Names()           // all service names
//	c.RegistryOf("actions").List("process.*")  // process capabilities
//	c.RegistryOf("commands").Len()             // command count
func (c *Core) RegistryOf(name string) *Registry[any] {
	// Bridge typed registries to untyped access for cross-cutting queries.
	// Each registry is wrapped in a read-only proxy.
	switch name {
	case "services":
		return registryProxy(c.services.Registry)
	case "commands":
		return registryProxy(c.commands.Registry)
	case "actions":
		return registryProxy(c.ipc.actions)
	default:
		return NewRegistry[any]() // empty registry for unknown names
	}
}

// registryProxy creates a read-only any-typed view of a typed registry.
// Copies current state — not a live view (avoids type parameter leaking).
func registryProxy[T any](src *Registry[T]) *Registry[any] {
	proxy := NewRegistry[any]()
	src.Each(func(name string, item T) {
		proxy.Set(name, item)
	})
	return proxy
}

// --- Global Instance ---