package files

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"sync"
	"syscall"

	"github.com/google/uuid"
	"github.com/saracen/walker"

	"github.com/aptly-dev/aptly/aptly"
	"github.com/aptly-dev/aptly/utils"
)

// PackagePool is deduplicated storage of package files on filesystem
type PackagePool struct {
	sync.Mutex

	rootPath           string
	supportLegacyPaths bool
}

// Check interface
var (
	_ aptly.PackagePool      = (*PackagePool)(nil)
	_ aptly.LocalPackagePool = (*PackagePool)(nil)
)

// NewPackagePool creates new instance of PackagePool which specified root
func NewPackagePool(root string, supportLegacyPaths bool) *PackagePool {
	rootPath, err := filepath.Abs(root)
	if err != nil {
		panic(err)
	}

	return &PackagePool{
		rootPath:           rootPath,
		supportLegacyPaths: supportLegacyPaths,
	}
}

// LegacyPath returns path relative to pool's root for pre-1.1 aptly (based on MD5)
func (pool *PackagePool) LegacyPath(filename string, checksums *utils.ChecksumInfo) (string, error) {
	filename = filepath.Base(filename)
	if filename == "." || filename == "/" {
		return "", fmt.Errorf("filename %s is invalid", filename)
	}

	hashMD5 := checksums.MD5

	if len(hashMD5) < 4 {
		return "", fmt.Errorf("unable to compute pool location for filename %v, MD5 is missing", filename)
	}

	return filepath.Join(hashMD5[0:2], hashMD5[2:4], filename), nil
}

// buildPoolPath generates pool path based on file checksum
func (pool *PackagePool) buildPoolPath(filename string, checksums *utils.ChecksumInfo) (string, error) {
	filename = filepath.Base(filename)
	if filename == "." || filename == "/" {
		return "", fmt.Errorf("filename %s is invalid", filename)
	}

	hash := checksums.SHA256

	if len(hash) < 4 {
		// this should never happen in real life
		return "", fmt.Errorf("unable to compute pool location for filename %v, SHA256 is missing", filename)
	}

	return filepath.Join(hash[0:2], hash[2:4], hash[4:32]+"_"+filename), nil
}

// FilepathList returns file paths of all the files in the pool
func (pool *PackagePool) FilepathList(progress aptly.Progress) ([]string, error) {
	pool.Lock()
	defer pool.Unlock()

	dirs, err := os.ReadDir(pool.rootPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}

	if len(dirs) == 0 {
		return nil, nil
	}

	if progress != nil {
		progress.InitBar(int64(len(dirs)), false, aptly.BarGeneralBuildFileList)
		defer progress.ShutdownBar()
	}

	result := []string{}
	resultLock := &sync.Mutex{}

	for _, dir := range dirs {
		err = walker.Walk(filepath.Join(pool.rootPath, dir.Name()), func(path string, info os.FileInfo) error {
			if !info.IsDir() {
				resultLock.Lock()
				defer resultLock.Unlock()
				result = append(result, path[len(pool.rootPath)+1:])
			}
			return nil
		})
		if err != nil {
			return nil, err
		}

		if progress != nil {
			progress.AddBar(1)
		}
	}

	sort.Strings(result)
	return result, nil
}

// Remove deletes file in package pool returns its size
func (pool *PackagePool) Remove(path string) (size int64, err error) {
	pool.Lock()
	defer pool.Unlock()

	path = filepath.Join(pool.rootPath, path)

	info, err := os.Stat(path)
	if err != nil {
		return 0, err
	}

	err = os.Remove(path)
	return info.Size(), err
}

func (pool *PackagePool) ensureChecksums(poolPath, fullPoolPath string, checksumStorage aptly.ChecksumStorage) (targetChecksums *utils.ChecksumInfo, err error) {
	targetChecksums, err = checksumStorage.Get(poolPath)
	if err != nil {
		return
	}

	if targetChecksums == nil {
		// we don't have checksums stored yet for this file
		targetChecksums = &utils.ChecksumInfo{}
		*targetChecksums, err = utils.ChecksumsForFile(fullPoolPath)
		if err != nil {
			return
		}

		err = checksumStorage.Update(poolPath, targetChecksums)
	}

	return
}

// Verify checks whether file exists in the pool and fills back checksum info
//
// if poolPath is empty, poolPath is generated automatically based on checksum info (if available)
// in any case, if function returns true, it also fills back checksums with complete information about the file in the pool
func (pool *PackagePool) Verify(poolPath, basename string, checksums *utils.ChecksumInfo, checksumStorage aptly.ChecksumStorage) (string, bool, error) {
	possiblePoolPaths := []string{}

	if poolPath != "" {
		possiblePoolPaths = append(possiblePoolPaths, poolPath)
	} else {
		// try to guess
		if checksums.SHA256 != "" {
			modernPath, err := pool.buildPoolPath(basename, checksums)
			if err != nil {
				return "", false, err
			}
			possiblePoolPaths = append(possiblePoolPaths, modernPath)
		}

		if pool.supportLegacyPaths && checksums.MD5 != "" {
			legacyPath, err := pool.LegacyPath(basename, checksums)
			if err != nil {
				return "", false, err
			}
			possiblePoolPaths = append(possiblePoolPaths, legacyPath)
		}
	}

	for _, path := range possiblePoolPaths {
		fullPoolPath := filepath.Join(pool.rootPath, path)

		targetInfo, err := os.Stat(fullPoolPath)
		if err != nil {
			if !os.IsNotExist(err) {
				// unable to stat target location?
				return "", false, err
			}
			// doesn't exist, skip it
			continue
		}

		if targetInfo.Size() != checksums.Size {
			// oops, wrong file?
			continue
		}

		var targetChecksums *utils.ChecksumInfo
		targetChecksums, err = pool.ensureChecksums(path, fullPoolPath, checksumStorage)

		if err != nil {
			return "", false, err
		}

		if checksums.MD5 != "" && targetChecksums.MD5 != checksums.MD5 ||
			checksums.SHA256 != "" && targetChecksums.SHA256 != checksums.SHA256 {
			// wrong file?
			return "", false, nil
		}

		// fill back checksums
		*checksums = *targetChecksums
		return path, true, nil
	}

	return "", false, nil
}

// Import copies file into package pool
//
// - srcPath is full path to source file as it is now
// - basename is desired human-readable name (canonical filename)
// - checksums are used to calculate file placement
// - move indicates whether srcPath can be removed
func (pool *PackagePool) Import(srcPath, basename string, checksums *utils.ChecksumInfo, move bool, checksumStorage aptly.ChecksumStorage) (string, error) {
	pool.Lock()
	defer pool.Unlock()

	source, err := os.Open(srcPath)
	if err != nil {
		return "", err
	}
	defer func() {
            _ = source.Close()
	}()

	sourceInfo, err := source.Stat()
	if err != nil {
		return "", err
	}

	if checksums.MD5 == "" || checksums.SHA256 == "" || checksums.Size != sourceInfo.Size() {
		// need to update checksums, MD5 and SHA256 should be always defined
		*checksums, err = utils.ChecksumsForFile(srcPath)
		if err != nil {
			return "", err
		}
	}

	// build target path
	poolPath, err := pool.buildPoolPath(basename, checksums)
	if err != nil {
		return "", err
	}

	fullPoolPath := filepath.Join(pool.rootPath, poolPath)

	targetInfo, err := os.Stat(fullPoolPath)
	if err != nil {
		if !os.IsNotExist(err) {
			// unable to stat target location?
			return "", err
		}
	} else {
		// target already exists and same size
		if targetInfo.Size() == sourceInfo.Size() {
			var targetChecksums *utils.ChecksumInfo

			targetChecksums, err = pool.ensureChecksums(poolPath, fullPoolPath, checksumStorage)
			if err != nil {
				return "", err
			}

			*checksums = *targetChecksums
			return poolPath, nil
		}

		// trying to overwrite file?
		return "", fmt.Errorf("unable to import into pool: file %s already exists", fullPoolPath)
	}

	if pool.supportLegacyPaths {
		// file doesn't exist at new location, check legacy location
		var (
			legacyTargetInfo           os.FileInfo
			legacyPath, legacyFullPath string
		)

		legacyPath, err = pool.LegacyPath(basename, checksums)
		if err != nil {
			return "", err
		}
		legacyFullPath = filepath.Join(pool.rootPath, legacyPath)

		legacyTargetInfo, err = os.Stat(legacyFullPath)
		if err != nil {
			if !os.IsNotExist(err) {
				return "", err
			}
		} else {
			// legacy file exists
			if legacyTargetInfo.Size() == sourceInfo.Size() {
				// file exists at legacy path and it's same size, consider it's already in the pool
				var targetChecksums *utils.ChecksumInfo

				targetChecksums, err = pool.ensureChecksums(legacyPath, legacyFullPath, checksumStorage)
				if err != nil {
					return "", err
				}

				*checksums = *targetChecksums
				return legacyPath, nil
			}

			// size is different, import at new path
		}
	}

	// create subdirs as necessary
	poolDir := filepath.Dir(fullPoolPath)
	err = os.MkdirAll(poolDir, 0777)
	if err != nil {
		return "", err
	}

	// check if we can use hardlinks instead of copying/moving
	poolDirInfo, err := os.Stat(poolDir)
	if err != nil {
		return "", err
	}

	if poolDirInfo.Sys().(*syscall.Stat_t).Dev == sourceInfo.Sys().(*syscall.Stat_t).Dev {
		// same filesystem, try to use hardlink
		err = os.Link(srcPath, fullPoolPath)
	} else {
		err = os.ErrInvalid
	}

	if err != nil {
		// different filesystems or failed hardlink, fallback to copy
		var target *os.File
		target, err = os.Create(fullPoolPath)
		if err != nil {
			return "", err
		}
		defer func() {
			_ = target.Close()
		}()

		_, err = io.Copy(target, source)

		if err == nil {
			err = target.Close()
		}
	}

	if err == nil {
		if !checksums.Complete() {
			// need full checksums here
			*checksums, err = utils.ChecksumsForFile(srcPath)
			if err != nil {
				return "", err
			}
		}

		err = checksumStorage.Update(poolPath, checksums)
	}

	if err == nil && move {
		err = os.Remove(srcPath)
	}

	return poolPath, err
}

func (pool *PackagePool) Size(path string) (size int64, err error) {
	stat, err := pool.Stat(path)
	if err != nil {
		return 0, err
	}

	return stat.Size(), nil
}

// Open returns io.ReadCloser to access the file
func (pool *PackagePool) Open(path string) (aptly.ReadSeekerCloser, error) {
	return os.Open(filepath.Join(pool.rootPath, path))
}

// Stat returns Unix stat(2) info
func (pool *PackagePool) Stat(path string) (os.FileInfo, error) {
	return os.Stat(filepath.Join(pool.rootPath, path))
}

// Link generates hardlink to destination path
func (pool *PackagePool) Link(path, dstPath string) error {
	return os.Link(filepath.Join(pool.rootPath, path), dstPath)
}

// Symlink generates symlink to destination path
func (pool *PackagePool) Symlink(path, dstPath string) error {
	return os.Symlink(filepath.Join(pool.rootPath, path), dstPath)
}

// FullPath generates full path to the file in pool
//
// Please use with care: it's not supposed to be used to access files
func (pool *PackagePool) FullPath(path string) string {
	return filepath.Join(pool.rootPath, path)
}

// GenerateTempPath generates temporary path for download (which is fast to import into package pool later on)
func (pool *PackagePool) GenerateTempPath(filename string) (string, error) {
	random := uuid.NewString()

	return filepath.Join(pool.rootPath, random[0:2], random[2:4], random[4:]+filename), nil
}