package storage

import (
	"context"
	"fmt"
	"slices"

	"github.com/canonical/lxd/lxd/db"
	"github.com/canonical/lxd/lxd/instance"
	"github.com/canonical/lxd/lxd/project"
	"github.com/canonical/lxd/lxd/response"
	"github.com/canonical/lxd/lxd/state"
	"github.com/canonical/lxd/lxd/storage/drivers"
	"github.com/canonical/lxd/shared/api"
	"github.com/canonical/lxd/shared/logger"
)

// PoolIDTemporary is used to indicate a temporary pool instance that is not in the database.
const PoolIDTemporary = -1

// volIDFuncMake returns a function that can be supplied to the underlying storage drivers allowing
// them to lookup the volume ID for a specific volume type and volume name. This function is tied
// to the Pool ID that it is generated for, meaning the storage drivers do not need to know the ID
// of the pool they belong to, or do they need access to the database.
func volIDFuncMake(state *state.State, poolID int64) func(volType drivers.VolumeType, volName string) (int64, error) {
	// Return a function to retrieve a volume ID for a volume Name for use in driver.
	return func(volType drivers.VolumeType, volName string) (int64, error) {
		volTypeID, err := VolumeTypeToDBType(volType)
		if err != nil {
			return -1, err
		}

		// It is possible for the project name to be encoded into the volume name in the
		// format <project>_<volume>. However not all volume types currently use this
		// encoding format, so if there is no underscore in the volume name then we assume
		// the project is default.
		projectName := api.ProjectDefaultName

		// Currently only Containers, VMs and custom volumes support project level volumes.
		// This means that other volume types may have underscores in their names that don't
		// indicate the project name.
		switch volType {
		case drivers.VolumeTypeContainer, drivers.VolumeTypeVM:
			projectName, volName = project.InstanceParts(volName)
		case drivers.VolumeTypeCustom:
			projectName, volName = project.StorageVolumeParts(volName)
		}

		// Get the storage volume.
		var dbVolume *db.StorageVolume
		err = state.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
			dbVolume, err = tx.GetStoragePoolVolume(ctx, poolID, projectName, volTypeID, volName, true)
			return err
		})
		if err != nil {
			return -1, err
		}

		return dbVolume.ID, nil
	}
}

// commonRules returns a set of common validators.
func commonRules() *drivers.Validators {
	return &drivers.Validators{
		PoolRules:   validatePoolCommonRules,
		VolumeRules: validateVolumeCommonRules,
	}
}

// NewTemporary instantiates a temporary pool from config supplied and returns a Pool interface.
// Not all functionality will be available due to the lack of Pool ID.
// If the pool's driver is not recognised then drivers.ErrUnknownDriver is returned.
func NewTemporary(state *state.State, info *api.StoragePool) (Pool, error) {
	// Handle mock requests.
	if state.OS.MockMode {
		pool := mockBackend{}
		pool.name = info.Name
		pool.state = state
		pool.logger = logger.AddContext(logger.Ctx{"driver": "mock", "pool": pool.name})
		driver, err := drivers.Load(state, "mock", "", nil, pool.logger, nil, nil)
		if err != nil {
			return nil, err
		}

		pool.driver = driver

		return &pool, nil
	}

	var poolID int64 = PoolIDTemporary // Temporary as not in DB. Not all functionality will be available.

	// Ensure a config map exists.
	if info.Config == nil {
		info.Config = map[string]string{}
	}

	logger := logger.AddContext(logger.Ctx{"driver": info.Driver, "pool": info.Name})

	// Load the storage driver.
	driver, err := drivers.Load(state, info.Driver, info.Name, info.Config, logger, volIDFuncMake(state, poolID), commonRules())
	if err != nil {
		return nil, err
	}

	// Setup the pool struct.
	pool := lxdBackend{}
	pool.driver = driver
	pool.id = poolID
	pool.db = *info
	pool.name = info.Name
	pool.state = state
	pool.logger = logger
	pool.nodes = nil // TODO support clustering.

	return &pool, nil
}

// LoadByType loads a network by driver type.
func LoadByType(state *state.State, driverType string) (Type, error) {
	logger := logger.AddContext(logger.Ctx{"driver": driverType})

	driver, err := drivers.Load(state, driverType, "", nil, logger, nil, commonRules())
	if err != nil {
		return nil, err
	}

	// Setup the pool struct.
	pool := lxdBackend{}
	pool.state = state
	pool.driver = driver
	pool.id = PoolIDTemporary
	pool.logger = logger

	return &pool, nil
}

// LoadByRecord instantiates a pool from its record and returns a Pool interface.
// If the pool's driver is not recognised then drivers.ErrUnknownDriver is returned.
func LoadByRecord(s *state.State, poolID int64, poolInfo api.StoragePool, poolMembers map[int64]db.StoragePoolNode) (Pool, error) {
	// Ensure a config map exists.
	if poolInfo.Config == nil {
		poolInfo.Config = map[string]string{}
	}

	logger := logger.AddContext(logger.Ctx{"driver": poolInfo.Driver, "pool": poolInfo.Name})

	// Load the storage driver.
	driver, err := drivers.Load(s, poolInfo.Driver, poolInfo.Name, poolInfo.Config, logger, volIDFuncMake(s, poolID), commonRules())
	if err != nil {
		return nil, err
	}

	// Setup the pool struct.
	pool := lxdBackend{}
	pool.driver = driver
	pool.id = poolID
	pool.db = poolInfo
	pool.name = poolInfo.Name
	pool.state = s
	pool.logger = logger
	pool.nodes = poolMembers

	return &pool, nil
}

// LoadByName retrieves the pool from the database by its name and returns a Pool interface.
// If the pool's driver is not recognised then drivers.ErrUnknownDriver is returned.
func LoadByName(s *state.State, name string) (Pool, error) {
	// Handle mock requests.
	if s.OS.MockMode {
		pool := mockBackend{}
		pool.name = name
		pool.state = s
		pool.logger = logger.AddContext(logger.Ctx{"driver": "mock", "pool": pool.name})
		driver, err := drivers.Load(s, "mock", "", nil, pool.logger, nil, nil)
		if err != nil {
			return nil, err
		}

		pool.driver = driver

		return &pool, nil
	}

	var poolID int64
	var dbPool *api.StoragePool
	var poolNodes map[int64]db.StoragePoolNode

	err := s.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		var err error

		// Load the database record.
		poolID, dbPool, poolNodes, err = tx.GetStoragePoolInAnyState(ctx, name)

		return err
	})
	if err != nil {
		return nil, err
	}

	return LoadByRecord(s, poolID, *dbPool, poolNodes)
}

// LoadByInstance retrieves the pool from the database using the instance's pool.
// If the pool's driver is not recognised then drivers.ErrUnknownDriver is returned. If the pool's
// driver does not support the instance's type then drivers.ErrNotSupported is returned.
func LoadByInstance(s *state.State, inst instance.Instance) (Pool, error) {
	poolName, err := inst.StoragePool()
	if err != nil {
		return nil, fmt.Errorf("Failed getting instance storage pool name: %w", err)
	}

	pool, err := LoadByName(s, poolName)
	if err != nil {
		return nil, fmt.Errorf("Failed loading storage pool %q: %w", poolName, err)
	}

	volType, err := InstanceTypeToVolumeType(inst.Type())
	if err != nil {
		return nil, err
	}

	if slices.Contains(pool.Driver().Info().VolumeTypes, volType) {
		return pool, nil
	}

	// Return drivers not supported error for consistency with predefined errors returned by
	// LoadByName (which can return drivers.ErrUnknownDriver).
	return nil, drivers.ErrNotSupported
}

// IsAvailable checks if a pool is available.
func IsAvailable(poolName string) bool {
	unavailablePoolsMu.Lock()
	defer unavailablePoolsMu.Unlock()

	_, found := unavailablePools[poolName]
	return !found
}

// Patch applies specified patch to all storage pools.
// All storage pools must be available locally before any storage pools are patched.
func Patch(s *state.State, patchName string) error {
	unavailablePoolsMu.Lock()

	if len(unavailablePools) > 0 {
		unavailablePoolNames := make([]string, 0, len(unavailablePools))
		for unavailablePoolName := range unavailablePools {
			unavailablePoolNames = append(unavailablePoolNames, unavailablePoolName)
		}

		unavailablePoolsMu.Unlock()
		return fmt.Errorf("Unvailable storage pools: %v", unavailablePoolNames)
	}

	unavailablePoolsMu.Unlock()

	var pools []string

	err := s.DB.Cluster.Transaction(context.TODO(), func(ctx context.Context, tx *db.ClusterTx) error {
		var err error

		// Load all the pools.
		pools, err = tx.GetStoragePoolNames(ctx)

		return err
	})
	if err != nil {
		if response.IsNotFoundError(err) {
			return nil
		}

		return fmt.Errorf("Failed loading storage pool names: %w", err)
	}

	for _, poolName := range pools {
		pool, err := LoadByName(s, poolName)
		if err != nil {
			return fmt.Errorf("Failed loading storage pool %q: %w", poolName, err)
		}

		err = pool.ApplyPatch(patchName)
		if err != nil {
			return fmt.Errorf("Failed applying patch to pool %q: %w", poolName, err)
		}
	}

	return nil
}
