package util

import (
	"errors"
	"fmt"
	"io"
	"math/rand"
	"os"
	"os/user"
	"path/filepath"
	"strings"
	"time"

	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/datastore.go"
	b58 "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-base58"
	mh "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multihash"
	logging "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/op/go-logging"
)

// LogFormat is the format used for our logger.
var LogFormat = "%{color}%{time:01-02 15:04:05.9999} %{shortfile} %{level}: %{color:reset}%{message}"

// Debug is a global flag for debugging.
var Debug bool

// ErrNotImplemented signifies a function has not been implemented yet.
var ErrNotImplemented = errors.New("Error: not implemented yet.")

// ErrTimeout implies that a timeout has been triggered
var ErrTimeout = errors.New("Error: Call timed out.")

// ErrSeErrSearchIncomplete implies that a search type operation didnt
// find the expected node, but did find 'a' node.
var ErrSearchIncomplete = errors.New("Error: Search Incomplete.")

// ErrNotFound is returned when a search fails to find anything
var ErrNotFound = ds.ErrNotFound

// Key is a string representation of multihash for use with maps.
type Key string

// String returns Key in a b58 encoded string
func (k Key) String() string {
	return b58.Encode([]byte(k))
}

func (k Key) Pretty() string {
	return b58.Encode([]byte(k))
}

// DsKey returns a Datastore key
func (k Key) DsKey() ds.Key {
	return ds.NewKey(k.Pretty())
}

// KeyFromDsKey returns a Datastore key
func KeyFromDsKey(dsk ds.Key) Key {
	l := dsk.List()
	enc := l[len(l)-1]
	return Key(b58.Decode(enc))
}

// Hash is the global IPFS hash function. uses multihash SHA2_256, 256 bits
func Hash(data []byte) mh.Multihash {
	h, err := mh.Sum(data, mh.SHA2_256, -1)
	if err != nil {
		// this error can be safely ignored (panic) because multihash only fails
		// from the selection of hash function. If the fn + length are valid, it
		// won't error.
		panic("multihash failed to hash using SHA2_256.")
	}
	return h
}

// IsValidHash checks whether a given hash is valid (b58 decodable, len > 0)
func IsValidHash(s string) bool {
	out := b58.Decode(s)
	if out == nil || len(out) == 0 {
		return false
	}
	return true
}

// TildeExpansion expands a filename, which may begin with a tilde.
func TildeExpansion(filename string) (string, error) {
	if strings.HasPrefix(filename, "~/") {
		usr, err := user.Current()
		if err != nil {
			return "", err
		}

		dir := usr.HomeDir + "/"
		filename = strings.Replace(filename, "~/", dir, 1)
	}
	return filename, nil
}

// PErr is a shorthand printing function to output to Stderr.
func PErr(format string, a ...interface{}) {
	fmt.Fprintf(os.Stderr, format, a...)
}

// POut is a shorthand printing function to output to Stdout.
func POut(format string, a ...interface{}) {
	fmt.Fprintf(os.Stdout, format, a...)
}

// DErr is a shorthand debug printing function to output to Stderr.
// Will only print if Debug is true.
func DErr(format string, a ...interface{}) {
	if Debug {
		PErr(format, a...)
	}
}

// DOut is a shorthand debug printing function to output to Stdout.
// Will only print if Debug is true.
func DOut(format string, a ...interface{}) {
	if Debug {
		POut(format, a...)
	}
}

var loggers = []string{}

// SetupLogging will initialize the logger backend and set the flags.
func SetupLogging() {
	backend := logging.NewLogBackend(os.Stderr, "", 0)
	logging.SetBackend(backend)
	/*
		if Debug {
			logging.SetLevel(logging.DEBUG, "")
		} else {
			logging.SetLevel(logging.ERROR, "")
		}
	*/
	logging.SetFormatter(logging.MustStringFormatter(LogFormat))

	for _, n := range loggers {
		logging.SetLevel(logging.ERROR, n)
	}
}

// Logger retrieves a particular logger + initializes it at a particular level
func Logger(name string) *logging.Logger {
	log := logging.MustGetLogger(name)
	// logging.SetLevel(lvl, name) // can't set level here.
	loggers = append(loggers, name)
	return log
}

// ExpandPathnames takes a set of paths and turns them into absolute paths
func ExpandPathnames(paths []string) ([]string, error) {
	var out []string
	for _, p := range paths {
		abspath, err := filepath.Abs(p)
		if err != nil {
			return nil, err
		}
		out = append(out, abspath)
	}
	return out, nil
}

// byteChanReader wraps a byte chan in a reader
type byteChanReader struct {
	in  chan []byte
	buf []byte
}

func NewByteChanReader(in chan []byte) io.Reader {
	return &byteChanReader{in: in}
}

func (bcr *byteChanReader) Read(b []byte) (int, error) {
	if len(bcr.buf) == 0 {
		data, ok := <-bcr.in
		if !ok {
			return 0, io.EOF
		}
		bcr.buf = data
	}

	if len(bcr.buf) >= len(b) {
		copy(b, bcr.buf)
		bcr.buf = bcr.buf[len(b):]
		return len(b), nil
	}

	copy(b, bcr.buf)
	b = b[len(bcr.buf):]
	totread := len(bcr.buf)

	for data := range bcr.in {
		if len(data) > len(b) {
			totread += len(b)
			copy(b, data[:len(b)])
			bcr.buf = data[len(b):]
			return totread, nil
		}
		copy(b, data)
		totread += len(data)
		b = b[len(data):]
		if len(b) == 0 {
			return totread, nil
		}
	}
	return totread, io.EOF
}

type randGen struct {
	src rand.Source
}

func NewFastRand() io.Reader {
	return &randGen{rand.NewSource(time.Now().UnixNano())}
}

func (r *randGen) Read(p []byte) (n int, err error) {
	todo := len(p)
	offset := 0
	for {
		val := int64(r.src.Int63())
		for i := 0; i < 8; i++ {
			p[offset] = byte(val & 0xff)
			todo--
			if todo == 0 {
				return len(p), nil
			}
			offset++
			val >>= 8
		}
	}

	panic("unreachable")
}