package controller

import (
	"errors"
	"fmt"
	"time"

	e "galaxy/error"
	"galaxy/game/internal/model/game"

	"github.com/google/uuid"

	"galaxy/model/order"
	"galaxy/model/report"

	"galaxy/game/internal/repo"
)

// Service is the engine's application service: it owns persistence and exposes
// the operations the HTTP handlers invoke. It is safe for concurrent use —
// reads are lock-free and the writers that mutate the canonical state file
// (init/turn/banish) are serialised at the router by a shared LimitMiddleware.
type Service struct {
	repo *repo.Repo
}

// NewService opens the file-backed storage at storagePath and returns a ready
// Service. The directory must already exist and be writable.
func NewService(storagePath string) (*Service, error) {
	r, err := repo.NewFileRepo(storagePath)
	if err != nil {
		return nil, err
	}
	return &Service{repo: r}, nil
}

// GenerateGame initialises a fresh game in storage under the supplied
// canonical gameID. The orchestrator must allocate gameID before the engine
// container is started and pass it here as the request body of
// POST /api/v1/admin/init. A zero UUID is rejected with ErrGameInitNilUUID; an
// attempt to init on top of an existing state.json is rejected with
// ErrGameAlreadyInit.
func (s *Service) GenerateGame(gameID uuid.UUID, races []string) (game.State, error) {
	if gameID == uuid.Nil {
		return game.State{}, ErrGameInitNilUUID
	}

	if existing, loadErr := s.repo.LoadState(); loadErr == nil {
		return game.State{}, fmt.Errorf("%w: stored gameId=%s, requested=%s", ErrGameAlreadyInit, existing.ID, gameID)
	} else if !isGameNotInitialized(loadErr) {
		return game.State{}, fmt.Errorf("check existing state: %w", loadErr)
	}

	if _, err := NewGame(s.repo, gameID, races); err != nil {
		return game.State{}, err
	}

	return s.GameState()
}

// GenerateTurn advances the game by one turn (applying every stored order) and
// returns the resulting game state.
func (s *Service) GenerateTurn() (game.State, error) {
	if err := s.execute(func(_ uint, c *Controller) error { return c.MakeTurn() }); err != nil {
		return game.State{}, err
	}
	return s.GameState()
}

// isGameNotInitialized reports whether err is the engine's canonical
// "no state.json on disk" signal returned by Repo.LoadState on a fresh
// storage directory.
func isGameNotInitialized(err error) bool {
	var ge *e.GenericError
	return errors.As(err, &ge) && ge.Code == e.ErrGameNotInitialized
}

// LoadReport returns the stored turn report for actor at the given turn.
func (s *Service) LoadReport(actor string, turn uint) (r *report.Report, err error) {
	execErr := s.execute(func(_ uint, c *Controller) (exErr error) {
		id, exErr := c.RaceID(actor)
		if exErr == nil {
			r, exErr = s.repo.LoadReport(turn, id)
		}
		return
	})
	err = errors.Join(err, execErr)
	return
}

// ValidateOrder validates cmd against a transient view of the current state,
// records the per-command outcome on each command's meta, and stores the
// resulting order for the current turn. Game-state rejections are reported per
// command, not as a returned error.
func (s *Service) ValidateOrder(actor string, cmd ...order.DecodableCommand) (o *order.UserGamesOrder, err error) {
	err = s.execute(func(t uint, c *Controller) error {
		id, err := c.RaceID(actor)
		if err != nil {
			return err
		}
		if err := c.ValidateOrder(actor, cmd...); err != nil {
			return err
		}
		o = &order.UserGamesOrder{
			GameID:    c.Cache.g.ID,
			UpdatedAt: time.Now().UTC().UnixMilli(),
			Commands:  make([]order.DecodableCommand, len(cmd)),
		}
		copy(o.Commands, cmd)
		return s.repo.SaveOrder(t, id, o)
	})
	if err != nil {
		return nil, err
	}
	return
}

// FetchOrder returns the order actor stored for the given turn. ok is false
// when no order was ever stored.
func (s *Service) FetchOrder(actor string, turn uint) (o *order.UserGamesOrder, ok bool, err error) {
	err = s.execute(func(_ uint, c *Controller) error {
		id, err := c.RaceID(actor)
		if err != nil {
			return err
		}
		o, ok, err = s.repo.LoadOrder(turn, id)
		return err
	})
	if err != nil {
		return
	}
	return
}

// FetchBattle returns the battle report stored at turn under ID. exists is
// false when no such battle was recorded.
func (s *Service) FetchBattle(turn uint, ID uuid.UUID) (b *report.BattleReport, exists bool, err error) {
	err = s.execute(func(_ uint, c *Controller) error {
		b, exists, err = s.repo.LoadBattle(turn, ID)
		return err
	})
	return
}

// BanishRace deactivates actor's race after a permanent platform removal and
// persists the updated state.
func (s *Service) BanishRace(actor string) error {
	return s.execute(func(_ uint, c *Controller) error {
		if err := c.RaceBanish(actor); err != nil {
			return err
		}
		return c.saveState()
	})
}

// GameState loads the current state and projects it into the transport-facing
// game.State summary (player roster with planet counts and population).
func (s *Service) GameState() (game.State, error) {
	g, err := s.repo.LoadState()
	if err != nil {
		return game.State{}, err
	}

	result := &game.State{
		ID:       g.ID,
		Turn:     g.Turn,
		Stage:    g.Stage,
		Finished: g.Finished(),
		Players:  make([]game.PlayerState, len(g.Race)),
	}

	planetCount := make(map[uuid.UUID]uint)
	population := make(map[uuid.UUID]game.Float)

	for i := range g.Map.Planet {
		p := &g.Map.Planet[i]
		if p.Owner == nil {
			continue
		}
		owner := *p.Owner
		planetCount[owner] += 1
		population[owner] += p.Population
	}

	for i := range g.Race {
		r := &g.Race[i]
		result.Players[i].ID = r.ID
		result.Players[i].RaceName = r.Name
		result.Players[i].Planets = planetCount[r.ID]
		result.Players[i].Population = population[r.ID]
		result.Players[i].Extinct = r.Extinct
	}

	return *result, nil
}

// execute loads the current game state, wraps it in a Controller and runs
// consumer against it. Reads and writes are lock-free; concurrent writers to
// the state file (init/turn/banish) are serialised at the router by a shared
// LimitMiddleware, so this helper holds no lock of its own.
func (s *Service) execute(consumer func(uint, *Controller) error) error {
	g, err := s.repo.LoadState()
	if err != nil {
		return err
	}
	return consumer(g.Turn, &Controller{repo: s.repo, Cache: NewCache(g)})
}

// Controller is the per-turn execution context: a loaded game state (Cache)
// plus the repo it persists through. It carries the engine's game-logic
// methods (in command.go, order.go, generate_turn.go, …).
type Controller struct {
	repo  *repo.Repo
	Cache *Cache
}

func (c *Controller) saveState() error {
	return c.repo.SaveLastState(c.Cache.g)
}