package main

import (
	"bytes"
	"context"
	"crypto/md5"
	"errors"
	"fmt"
	"io"
	"os"
	"strings"
	"sync"
	"time"
)

// A TestableVolume allows test suites to manipulate the state of an
// underlying Volume, in order to test behavior in cases that are
// impractical to achieve with a sequence of normal Volume operations.
type TestableVolume interface {
	Volume
	// [Over]write content for a locator with the given data,
	// bypassing all constraints like readonly and serialize.
	PutRaw(locator string, data []byte)

	// Specify the value Mtime() should return, until the next
	// call to Touch, TouchWithDate, or Put.
	TouchWithDate(locator string, lastPut time.Time)

	// Clean up, delete temporary files.
	Teardown()
}

// MockVolumes are test doubles for Volumes, used to test handlers.
type MockVolume struct {
	Store      map[string][]byte
	Timestamps map[string]time.Time

	// Bad volumes return an error for every operation.
	Bad bool

	// Touchable volumes' Touch() method succeeds for a locator
	// that has been Put().
	Touchable bool

	// Readonly volumes return an error for Put, Delete, and
	// Touch.
	Readonly bool

	// Gate is a "starting gate", allowing test cases to pause
	// volume operations long enough to inspect state. Every
	// operation (except Status) starts by receiving from
	// Gate. Sending one value unblocks one operation; closing the
	// channel unblocks all operations. By default, Gate is a
	// closed channel, so all operations proceed without
	// blocking. See trash_worker_test.go for an example.
	Gate chan struct{}

	called map[string]int
	mutex  sync.Mutex
}

// CreateMockVolume returns a non-Bad, non-Readonly, Touchable mock
// volume.
func CreateMockVolume() *MockVolume {
	gate := make(chan struct{})
	close(gate)
	return &MockVolume{
		Store:      make(map[string][]byte),
		Timestamps: make(map[string]time.Time),
		Bad:        false,
		Touchable:  true,
		Readonly:   false,
		called:     map[string]int{},
		Gate:       gate,
	}
}

// CallCount returns how many times the named method has been called.
func (v *MockVolume) CallCount(method string) int {
	v.mutex.Lock()
	defer v.mutex.Unlock()
	c, ok := v.called[method]
	if !ok {
		return 0
	}
	return c
}

func (v *MockVolume) gotCall(method string) {
	v.mutex.Lock()
	defer v.mutex.Unlock()
	if _, ok := v.called[method]; !ok {
		v.called[method] = 1
	} else {
		v.called[method]++
	}
}

func (v *MockVolume) Compare(loc string, buf []byte) error {
	v.gotCall("Compare")
	<-v.Gate
	if v.Bad {
		return errors.New("Bad volume")
	} else if block, ok := v.Store[loc]; ok {
		if fmt.Sprintf("%x", md5.Sum(block)) != loc {
			return DiskHashError
		}
		if bytes.Compare(buf, block) != 0 {
			return CollisionError
		}
		return nil
	} else {
		return NotFoundError
	}
}

func (v *MockVolume) Get(ctx context.Context, loc string, buf []byte) (int, error) {
	v.gotCall("Get")
	<-v.Gate
	if v.Bad {
		return 0, errors.New("Bad volume")
	} else if block, ok := v.Store[loc]; ok {
		copy(buf[:len(block)], block)
		return len(block), nil
	}
	return 0, os.ErrNotExist
}

func (v *MockVolume) Put(ctx context.Context, loc string, block []byte) error {
	v.gotCall("Put")
	<-v.Gate
	if v.Bad {
		return errors.New("Bad volume")
	}
	if v.Readonly {
		return MethodDisabledError
	}
	v.Store[loc] = block
	return v.Touch(loc)
}

func (v *MockVolume) Touch(loc string) error {
	v.gotCall("Touch")
	<-v.Gate
	if v.Readonly {
		return MethodDisabledError
	}
	if v.Touchable {
		v.Timestamps[loc] = time.Now()
		return nil
	}
	return errors.New("Touch failed")
}

func (v *MockVolume) Mtime(loc string) (time.Time, error) {
	v.gotCall("Mtime")
	<-v.Gate
	var mtime time.Time
	var err error
	if v.Bad {
		err = errors.New("Bad volume")
	} else if t, ok := v.Timestamps[loc]; ok {
		mtime = t
	} else {
		err = os.ErrNotExist
	}
	return mtime, err
}

func (v *MockVolume) IndexTo(prefix string, w io.Writer) error {
	v.gotCall("IndexTo")
	<-v.Gate
	for loc, block := range v.Store {
		if !IsValidLocator(loc) || !strings.HasPrefix(loc, prefix) {
			continue
		}
		_, err := fmt.Fprintf(w, "%s+%d %d\n",
			loc, len(block), 123456789)
		if err != nil {
			return err
		}
	}
	return nil
}

func (v *MockVolume) Trash(loc string) error {
	v.gotCall("Delete")
	<-v.Gate
	if v.Readonly {
		return MethodDisabledError
	}
	if _, ok := v.Store[loc]; ok {
		if time.Since(v.Timestamps[loc]) < time.Duration(theConfig.BlobSignatureTTL) {
			return nil
		}
		delete(v.Store, loc)
		return nil
	}
	return os.ErrNotExist
}

func (v *MockVolume) Type() string {
	return "Mock"
}

func (v *MockVolume) Start() error {
	return nil
}

func (v *MockVolume) Untrash(loc string) error {
	return nil
}

func (v *MockVolume) Status() *VolumeStatus {
	var used uint64
	for _, block := range v.Store {
		used = used + uint64(len(block))
	}
	return &VolumeStatus{"/bogo", 123, 1000000 - used, used}
}

func (v *MockVolume) String() string {
	return "[MockVolume]"
}

func (v *MockVolume) Writable() bool {
	return !v.Readonly
}

func (v *MockVolume) Replication() int {
	return 1
}

func (v *MockVolume) EmptyTrash() {
}