package megauploader

import (
	"fmt"
	"io"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strings"

	"github.com/c2h5oh/datasize"
	"github.com/pkg/errors"
	glob "github.com/ryanuber/go-glob"
)

// helpers {{{

// Globs is an array of globs with convenience methods
type Globs []string

// Has check if any of the  Glob matches with needle
func (gs Globs) Has(needle string) bool {
	for _, g := range gs {
		if glob.Glob(g, needle) {
			return true
		}
	}
	return false
}

// ExtensionList is a list of extensions; you MUST NOT include the dot. That is, it must be
//      {"mp3", "ogg", "aac"}
// not
//      {".docx", ".odt"}
type ExtensionList []string

// Matches check if the provided filename matches any of the extension
func (el *ExtensionList) Matches(needle string) bool {
	if len(*el) == 0 {
		return true
	}
	n := strings.ToLower(needle)
	for _, ext := range *el {
		if strings.HasSuffix(n, fmt.Sprintf(".%s", strings.ToLower(ext))) {
			return true
		}
	}
	return false
}

// }}}

// Config contains the whole configuration
type Config struct {
	Global   Global    `yaml:"global"`
	UserHome *UserHome `yaml:"userhome"`
	Shares   []Share   `yaml:"shares"`
}

// Pretty returns a pretty-printed representation of the Config data
func (c Config) Pretty() string {
	return fmt.Sprintf("GLOBAL\n%+v\nHOME\n%+v\nSHARES\n%+v\n", c.Global, *(c.UserHome), c.Shares)
}

// Validate checks the config for blocking inconsistencies
//
// while at the moment this does few checks, expect it to act on the conservative side
//
// returns a slice of errors; so check with
//     if errs := conf.Validate(); len(errs) != 0
func (c Config) Validate() []error {
	errs := make([]error, 0)
	names := make([]string, len(c.Shares))
	if c.Shares != nil {
		for i, s := range c.Shares {
			names[i] = s.Name
		}
		sort.Strings(names)
		i := 0
		for i < len(names)-1 {
			if names[i] == names[i+1] {
				errs = append(errs, fmt.Errorf("Duplicate '%s' shares", names[i]))
			}
			i++
		}

		for i, s := range c.Shares {
			// shareRef is a human-understandable,
			// 1-indexed reference to this share
			shareRef := fmt.Sprintf("Share %d(%s)", i+1, s.Name)
			if s.Name == "" {
				errs = append(errs, fmt.Errorf("%s has no name", shareRef))
			}
			if s.Dir == "" {
				errs = append(errs, fmt.Errorf("%s has no dir", shareRef))
			} else {
				var fi os.FileInfo
				var err error
				if fi, err = os.Stat(s.Dir); err != nil {
					errs = append(errs, fmt.Errorf("error accessing dir %s for %s", s.Dir, shareRef))
				} else {
					if !fi.IsDir() {
						errs = append(errs, fmt.Errorf("dir %s for %s is not a dir", s.Dir, shareRef))
					}
				}
			}
		}
	}

	if c.UserHome != nil && c.UserHome.BasePath == "" {
		errs = append(errs, errors.New("UserHome requires a BasePath: fill it or omit it"))
	}

	if (c.Global.ViewPathBase == "") != (c.Global.ViewURLBase == "") {
		errs = append(errs, errors.New("viewpathbase and viewurlbase must be both set, or none"))
	}

	return errs
}

// Global is the global section of the configuration
type Global struct {
	Excluded     Globs  `yaml:"excluded"`
	ViewURLBase  string `yaml:"viewurlbase"`
	ViewPathBase string `yaml:"viewpathbase"`
	RoutePrefix  string `yaml:"routeprefix"` // if you want to proxy megauploader as a sub-location, that's for you
}

// UserHome specifies rules for generating home shares on the fly
type UserHome struct {
	BasePath string `yaml:"basepath"`
	Create   bool   `yaml:"create"`
}

// A Share is a directory where users can upload files
type Share struct {
	Name        string            `yaml:"name"`
	Dir         string            `yaml:"dir"`
	Description string            `yaml:"description"`
	Authorized  Globs             `yaml:"authorized"`
	SizeLimit   datasize.ByteSize `yaml:"sizelimit"`
	Extensions  ExtensionList     `yaml:"extensions"`
}

// IsAuthorized checks whether username is autorized to access the Share
func (s Share) IsAuthorized(username string) bool {
	return s.Authorized.Has(username)
}

// Upload let you create a new file in the share
//
// If a file with the same name exists, Upload will try to "increment"
// it. If no valid filename is found, an error will be returned.
//
// FIXME: distinguish between validation errors and server errors
func (s Share) Upload(buf io.Reader, filename string) (string, error) {
	if !s.Extensions.Matches(filename) {
		return "", fmt.Errorf("Extension not admitted for this share")
	}
	fpath := filepath.Join(s.Dir, filename)
	incrementable := newFileIncrement(fpath)
	var dst *os.File
	var err error
	var realFileName string

	try := 0
	for try < 10 {
		realFileName = incrementable.Increment(try)
		dst, err = os.OpenFile(realFileName,
			os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
		if err == nil {
			break
		}
		try++
	}
	if try == 10 {
		return "", fmt.Errorf("Can't create file %s", filename)
	}
	defer dst.Close()
	_, err = io.Copy(dst, buf)
	return realFileName, nil
}

// GetViewURL retrieves the view URL for the specified path
func (g *Global) GetViewURL(dir string) (url.URL, error) {
	rel, err := filepath.Rel(g.ViewPathBase, dir)
	if err != nil {
		return url.URL{}, errors.Wrapf(err, "Error getting view URL for '%s'", dir)
	}
	if strings.HasPrefix(rel, "../") {
		return url.URL{}, fmt.Errorf("Error getting view URL for '%s'", dir)
	}
	u, err := url.Parse(g.ViewURLBase)
	if err != nil {
		return url.URL{}, fmt.Errorf("Invalid view URL %s", g.ViewURLBase)
	}
	u.Path = path.Join(u.Path, rel)
	return *u, nil
}

// GetShareURL retrieves the view URL for the share identified by sharename
func (c *Config) GetShareURL(sharename string) (url.URL, error) {
	if c.Global.ViewPathBase == "" || c.Global.ViewURLBase == "" {
		return url.URL{}, errors.New("View URL not configured")
	}
	s, err := c.GetShare(sharename)
	if err != nil {
		return url.URL{}, err
	}
	return c.Global.GetViewURL(s.Dir)
}

// GetAuthShares returns an array of all the shares the user is authorized to use, including its home.
func (c *Config) GetAuthShares(username string) []Share {
	shares := make([]Share, 0)
	if c.Global.Excluded.Has(username) {
		return shares
	}
	for _, s := range c.Shares {
		if s.IsAuthorized(username) {
			shares = append(shares, s)
		}
	}
	home, err := c.GetHome(username)
	if err == nil {
		shares = append(shares, *home)
	}
	return shares
}

// GetAuthShare returns a valid share for a certain user.
//
// It includes checking for permissions and dynamically-generated home.
//
// FIXME: can't tell 'unauthorized' from 'not found'
func (c *Config) GetAuthShare(sharename string, username string) (Share, error) {
	share, err := c.GetShare(sharename)
	if err == nil {
		if share.IsAuthorized(username) {
			return share, nil
		}
		return Share{}, errors.New("Unauthorized")
	}
	home, homeerr := c.GetHome(username)
	if homeerr != nil || home.Name != sharename {
		return Share{}, errors.New("Cannot find home")
	}
	// assuming user is always authorized on its dynamically-generated home
	return *home, nil
}

func (c *Config) GetShare(name string) (Share, error) {
	for _, share := range c.Shares {
		if share.Name == name {
			return share, nil
		}
	}
	return Share{}, errors.New("share not found")
}

// GetHome returns the home share for a user, if available
// It implements authorization check
func (c *Config) GetHome(username string) (*Share, error) {
	// explicit share gets precedence
	sharename := fmt.Sprintf("home_%s", username)
	share, err := c.GetShare(sharename)
	if err == nil {
		if share.IsAuthorized(username) {
			return &share, nil
		}
		return nil, fmt.Errorf("Home share for %s is forbidden to its owner", username)
	}
	if c.Global.Excluded.Has(username) {
		return nil, fmt.Errorf("User %s has no home", username)
	}
	s := new(Share)
	s.Name = sharename
	s.Authorized = Globs{username}
	s.Dir = filepath.Join(c.UserHome.BasePath, username)
	stat, err := os.Stat(s.Dir)
	if err != nil {
		if os.IsNotExist(err) { //doesn't exist
			if c.UserHome.Create {
				os.Mkdir(s.Dir, os.ModeDir)
			} else {
				return nil, fmt.Errorf("User %s home is non-existent (and we won't create it)", username)
			}
		} else {
			return nil, errors.Wrapf(err, "access to %s'shome failed", username)
		}
	} else {
		if !stat.IsDir() {
			return nil, fmt.Errorf("%s's home exists but is not a directory", username)
		}
	}
	s.Description = fmt.Sprintf("%s's home", username)

	return s, nil
}

// URLFetcher is a WIP section of the config to define rules for fetching URLs instead of uploading
type URLFetcher struct {
	Enabled     bool
	AllowedURLs Globs
	SizeLimit   datasize.ByteSize
}