package lib

import (
	"io"
	"sync"
	"time"

	"git.sr.ht/~rjarry/aerc/lib/sort"
	"git.sr.ht/~rjarry/aerc/logging"
	"git.sr.ht/~rjarry/aerc/models"
	"git.sr.ht/~rjarry/aerc/worker/types"
)

// Accesses to fields must be guarded by MessageStore.Lock/Unlock
type MessageStore struct {
	Deleted  map[uint32]interface{}
	DirInfo  models.DirectoryInfo
	Messages map[uint32]*models.MessageInfo
	Sorting  bool

	// Ordered list of known UIDs
	uids    []uint32
	threads []*types.Thread

	selectedUid     uint32
	reselect        *models.MessageInfo
	bodyCallbacks   map[uint32][]func(*types.FullMessage)
	headerCallbacks map[uint32][]func(*types.MessageInfo)

	// marking
	marked         map[uint32]struct{}
	lastMarked     map[uint32]struct{}
	visualStartUid uint32
	visualMarkMode bool

	// Search/filter results
	results     []uint32
	resultIndex int
	filter      []string

	sortCriteria []*types.SortCriterion

	threadedView bool
	buildThreads bool
	builder      *ThreadBuilder

	// Map of uids we've asked the worker to fetch
	onUpdate       func(store *MessageStore) // TODO: multiple onUpdate handlers
	onFilterChange func(store *MessageStore)
	onUpdateDirs   func()
	pendingBodies  map[uint32]interface{}
	pendingHeaders map[uint32]interface{}
	worker         *types.Worker

	triggerNewEmail        func(*models.MessageInfo)
	triggerDirectoryChange func()

	threadBuilderDebounce *time.Timer
	threadBuilderDelay    time.Duration

	threadsMutex sync.Mutex
}

const MagicUid = 0xFFFFFFFF

func NewMessageStore(worker *types.Worker,
	dirInfo *models.DirectoryInfo,
	defaultSortCriteria []*types.SortCriterion,
	thread bool, clientThreads bool, clientThreadsDelay time.Duration,
	triggerNewEmail func(*models.MessageInfo),
	triggerDirectoryChange func(),
) *MessageStore {
	if !dirInfo.Caps.Thread {
		clientThreads = true
	}

	return &MessageStore{
		Deleted:  make(map[uint32]interface{}),
		DirInfo:  *dirInfo,
		Messages: make(map[uint32]*models.MessageInfo),

		selectedUid:     MagicUid,
		marked:          make(map[uint32]struct{}),
		bodyCallbacks:   make(map[uint32][]func(*types.FullMessage)),
		headerCallbacks: make(map[uint32][]func(*types.MessageInfo)),

		threadedView: thread,
		buildThreads: clientThreads,

		filter:       []string{"filter"},
		sortCriteria: defaultSortCriteria,

		pendingBodies:  make(map[uint32]interface{}),
		pendingHeaders: make(map[uint32]interface{}),
		worker:         worker,

		triggerNewEmail:        triggerNewEmail,
		triggerDirectoryChange: triggerDirectoryChange,

		threadBuilderDelay: clientThreadsDelay,
	}
}

func (store *MessageStore) FetchHeaders(uids []uint32,
	cb func(*types.MessageInfo),
) {
	// TODO: this could be optimized by pre-allocating toFetch and trimming it
	// at the end. In practice we expect to get most messages back in one frame.
	var toFetch []uint32
	for _, uid := range uids {
		if _, ok := store.pendingHeaders[uid]; !ok {
			toFetch = append(toFetch, uid)
			store.pendingHeaders[uid] = nil
			if cb != nil {
				if list, ok := store.headerCallbacks[uid]; ok {
					store.headerCallbacks[uid] = append(list, cb)
				} else {
					store.headerCallbacks[uid] = []func(*types.MessageInfo){cb}
				}
			}
		}
	}
	if len(toFetch) > 0 {
		store.worker.PostAction(&types.FetchMessageHeaders{Uids: toFetch}, func(msg types.WorkerMessage) {
			switch msg.(type) {
			case *types.Error:
				for _, uid := range toFetch {
					delete(store.pendingHeaders, uid)
					delete(store.headerCallbacks, uid)
				}
			}
		})
	}
}

func (store *MessageStore) FetchFull(uids []uint32, cb func(*types.FullMessage)) {
	// TODO: this could be optimized by pre-allocating toFetch and trimming it
	// at the end. In practice we expect to get most messages back in one frame.
	var toFetch []uint32
	for _, uid := range uids {
		if _, ok := store.pendingBodies[uid]; !ok {
			toFetch = append(toFetch, uid)
			store.pendingBodies[uid] = nil
			if cb != nil {
				if list, ok := store.bodyCallbacks[uid]; ok {
					store.bodyCallbacks[uid] = append(list, cb)
				} else {
					store.bodyCallbacks[uid] = []func(*types.FullMessage){cb}
				}
			}
		}
	}
	if len(toFetch) > 0 {
		store.worker.PostAction(&types.FetchFullMessages{
			Uids: toFetch,
		}, func(msg types.WorkerMessage) {
			switch msg.(type) {
			case *types.Error:
				for _, uid := range toFetch {
					delete(store.pendingBodies, uid)
					delete(store.bodyCallbacks, uid)
				}
			}
		})
	}
}

func (store *MessageStore) FetchBodyPart(uid uint32, part []int, cb func(io.Reader)) {
	store.worker.PostAction(&types.FetchMessageBodyPart{
		Uid:  uid,
		Part: part,
	}, func(resp types.WorkerMessage) {
		msg, ok := resp.(*types.MessageBodyPart)
		if !ok {
			return
		}
		cb(msg.Part.Reader)
	})
}

func merge(to *models.MessageInfo, from *models.MessageInfo) {
	if from.BodyStructure != nil {
		to.BodyStructure = from.BodyStructure
	}
	if from.Envelope != nil {
		to.Envelope = from.Envelope
	}
	to.Flags = from.Flags
	to.Labels = from.Labels
	if from.Size != 0 {
		to.Size = from.Size
	}
	var zero time.Time
	if from.InternalDate != zero {
		to.InternalDate = from.InternalDate
	}
}

func (store *MessageStore) Update(msg types.WorkerMessage) {
	update := false
	directoryChange := false
	switch msg := msg.(type) {
	case *types.DirectoryInfo:
		store.DirInfo = *msg.Info
		if !msg.SkipSort {
			store.Sort(store.sortCriteria, nil)
		}
		update = true
	case *types.DirectoryContents:
		newMap := make(map[uint32]*models.MessageInfo)
		for _, uid := range msg.Uids {
			if msg, ok := store.Messages[uid]; ok {
				newMap[uid] = msg
			} else {
				newMap[uid] = nil
				directoryChange = true
			}
		}
		store.Messages = newMap
		store.uids = msg.Uids
		store.checkMark()
		update = true
	case *types.DirectoryThreaded:
		var uids []uint32
		newMap := make(map[uint32]*models.MessageInfo)

		for i := len(msg.Threads) - 1; i >= 0; i-- {
			_ = msg.Threads[i].Walk(func(t *types.Thread, level int, currentErr error) error {
				uid := t.Uid
				uids = append([]uint32{uid}, uids...)
				if msg, ok := store.Messages[uid]; ok {
					newMap[uid] = msg
				} else {
					newMap[uid] = nil
					directoryChange = true
				}
				return nil
			})
		}
		store.Messages = newMap
		store.uids = uids
		store.checkMark()
		store.threads = msg.Threads
		update = true
	case *types.MessageInfo:
		if existing, ok := store.Messages[msg.Info.Uid]; ok && existing != nil {
			merge(existing, msg.Info)
		} else {
			if msg.Info.Envelope != nil {
				store.Messages[msg.Info.Uid] = msg.Info
			}
		}
		seen := false
		recent := false
		for _, flag := range msg.Info.Flags {
			if flag == models.RecentFlag {
				recent = true
			} else if flag == models.SeenFlag {
				seen = true
			}
		}
		if !seen && recent {
			store.triggerNewEmail(msg.Info)
		}
		if _, ok := store.pendingHeaders[msg.Info.Uid]; msg.Info.Envelope != nil && ok {
			delete(store.pendingHeaders, msg.Info.Uid)
			if cbs, ok := store.headerCallbacks[msg.Info.Uid]; ok {
				for _, cb := range cbs {
					cb(msg)
				}
			}
		}
		if store.builder != nil {
			store.builder.Update(msg.Info)
		}
		update = true
	case *types.FullMessage:
		if _, ok := store.pendingBodies[msg.Content.Uid]; ok {
			delete(store.pendingBodies, msg.Content.Uid)
			if cbs, ok := store.bodyCallbacks[msg.Content.Uid]; ok {
				for _, cb := range cbs {
					cb(msg)
				}
				delete(store.bodyCallbacks, msg.Content.Uid)
			}
		}
	case *types.MessagesDeleted:
		if len(store.uids) < len(msg.Uids) {
			update = true
			break
		}

		toDelete := make(map[uint32]interface{})
		for _, uid := range msg.Uids {
			toDelete[uid] = nil
			delete(store.Messages, uid)
			delete(store.Deleted, uid)
			delete(store.marked, uid)
		}
		uids := make([]uint32, len(store.uids)-len(msg.Uids))
		j := 0
		for _, uid := range store.uids {
			if _, deleted := toDelete[uid]; !deleted && j < len(uids) {
				uids[j] = uid
				j += 1
			}
		}
		store.uids = uids

		var newResults []uint32
		for _, res := range store.results {
			if _, deleted := toDelete[res]; !deleted {
				newResults = append(newResults, res)
			}
		}
		store.results = newResults

		for _, thread := range store.Threads() {
			_ = thread.Walk(func(t *types.Thread, _ int, _ error) error {
				if _, deleted := toDelete[t.Uid]; deleted {
					t.Deleted = true
				}
				return nil
			})
		}

		update = true
	}

	if update {
		store.update()
	}

	if directoryChange && store.triggerDirectoryChange != nil {
		store.triggerDirectoryChange()
	}
}

func (store *MessageStore) OnUpdate(fn func(store *MessageStore)) {
	store.onUpdate = fn
}

func (store *MessageStore) OnFilterChange(fn func(store *MessageStore)) {
	store.onFilterChange = fn
}

func (store *MessageStore) OnUpdateDirs(fn func()) {
	store.onUpdateDirs = fn
}

func (store *MessageStore) update() {
	if store.onUpdate != nil {
		store.onUpdate(store)
	}
	if store.onUpdateDirs != nil {
		store.onUpdateDirs()
	}
	if store.BuildThreads() && store.ThreadedView() {
		store.runThreadBuilder()
	}
}

func (store *MessageStore) SetThreadedView(thread bool) {
	store.threadedView = thread
	if store.buildThreads {
		if store.threadedView {
			store.runThreadBuilder()
		}
		return
	}
	store.Sort(store.sortCriteria, nil)
}

func (store *MessageStore) Threads() []*types.Thread {
	store.threadsMutex.Lock()
	defer store.threadsMutex.Unlock()
	return store.threads
}

func (store *MessageStore) ThreadedView() bool {
	return store.threadedView
}

func (store *MessageStore) BuildThreads() bool {
	return store.buildThreads
}

func (store *MessageStore) runThreadBuilder() {
	if store.builder == nil {
		store.builder = NewThreadBuilder()
		for _, msg := range store.Messages {
			store.builder.Update(msg)
		}
	}
	if store.threadBuilderDebounce != nil {
		if store.threadBuilderDebounce.Stop() {
			logging.Infof("thread builder debounced")
		}
	}
	store.threadBuilderDebounce = time.AfterFunc(store.threadBuilderDelay, func() {
		// temporarily deactiviate the selector in the message list by
		// setting SelectedUid to the MagicUid
		oldUid := store.SelectedUid()
		store.Select(MagicUid)

		// Get the current index (we want to stay at that position in
		// the updated uid list to provide a similar scrolling
		// experience to the user as in the regular view
		idx := store.FindIndexByUid(oldUid)

		// build new threads
		th := store.builder.Threads(store.uids)

		// try to select the same index in the updated uid list; if
		// index is out of bound, stay at the selected message
		rebuildUids := store.builder.Uids()
		if idx >= 0 && idx < len(rebuildUids) {
			store.Select(rebuildUids[idx])
		} else {
			store.Select(oldUid)
		}

		// save local threads to the message store variable
		store.threadsMutex.Lock()
		store.threads = th
		store.threadsMutex.Unlock()

		// invalidate message list so that it is redrawn with the new
		// threads and selected message
		if store.onUpdate != nil {
			store.onUpdate(store)
		}
	})
}

func (store *MessageStore) Delete(uids []uint32,
	cb func(msg types.WorkerMessage),
) {
	for _, uid := range uids {
		store.Deleted[uid] = nil
	}

	store.worker.PostAction(&types.DeleteMessages{Uids: uids},
		func(msg types.WorkerMessage) {
			switch msg.(type) {
			case *types.Error:
				store.revertDeleted(uids)
			}
			cb(msg)
		})
}

func (store *MessageStore) revertDeleted(uids []uint32) {
	for _, uid := range uids {
		delete(store.Deleted, uid)
	}
}

func (store *MessageStore) Copy(uids []uint32, dest string, createDest bool,
	cb func(msg types.WorkerMessage),
) {
	if createDest {
		store.worker.PostAction(&types.CreateDirectory{
			Directory: dest,
			Quiet:     true,
		}, cb)
	}

	store.worker.PostAction(&types.CopyMessages{
		Destination: dest,
		Uids:        uids,
	}, cb)
}

func (store *MessageStore) Move(uids []uint32, dest string, createDest bool,
	cb func(msg types.WorkerMessage),
) {
	for _, uid := range uids {
		store.Deleted[uid] = nil
	}

	if createDest {
		store.worker.PostAction(&types.CreateDirectory{
			Directory: dest,
			Quiet:     true,
		}, nil) // quiet doesn't return an error, don't want the done cb here
	}

	store.worker.PostAction(&types.CopyMessages{
		Destination: dest,
		Uids:        uids,
	}, func(msg types.WorkerMessage) {
		switch msg.(type) {
		case *types.Error:
			store.revertDeleted(uids)
			cb(msg)
		case *types.Done:
			store.Delete(uids, cb)
		}
	})
}

func (store *MessageStore) Flag(uids []uint32, flag models.Flag,
	enable bool, cb func(msg types.WorkerMessage),
) {
	store.worker.PostAction(&types.FlagMessages{
		Enable: enable,
		Flag:   flag,
		Uids:   uids,
	}, cb)
}

func (store *MessageStore) Answered(uids []uint32, answered bool,
	cb func(msg types.WorkerMessage),
) {
	store.worker.PostAction(&types.AnsweredMessages{
		Answered: answered,
		Uids:     uids,
	}, cb)
}

func (store *MessageStore) Uids() []uint32 {
	if store.ThreadedView() && store.builder != nil {
		if uids := store.builder.Uids(); len(uids) > 0 {
			return uids
		}
	}
	return store.uids
}

func (store *MessageStore) Selected() *models.MessageInfo {
	return store.Messages[store.selectedUid]
}

func (store *MessageStore) SelectedUid() uint32 {
	if store.selectedUid == MagicUid && len(store.Uids()) > 0 {
		uids := store.Uids()
		store.selectedUid = uids[len(uids)-1]
	}
	return store.selectedUid
}

func (store *MessageStore) Select(uid uint32) {
	store.selectedUid = uid
	store.updateVisual()
}

// Mark sets the marked state on a MessageInfo
func (store *MessageStore) Mark(uid uint32) {
	if store.visualMarkMode {
		// visual mode has override, bogus input from user
		return
	}
	store.marked[uid] = struct{}{}
}

// Unmark removes the marked state on a MessageInfo
func (store *MessageStore) Unmark(uid uint32) {
	if store.visualMarkMode {
		// user probably wanted to clear the visual marking
		store.ClearVisualMark()
		return
	}
	delete(store.marked, uid)
}

func (store *MessageStore) Remark() {
	store.marked = store.lastMarked
}

// ToggleMark toggles the marked state on a MessageInfo
func (store *MessageStore) ToggleMark(uid uint32) {
	if store.visualMarkMode {
		// visual mode has override, bogus input from user
		return
	}
	if store.IsMarked(uid) {
		store.Unmark(uid)
	} else {
		store.Mark(uid)
	}
}

// resetMark removes the marking from all messages
func (store *MessageStore) resetMark() {
	store.lastMarked = store.marked
	store.marked = make(map[uint32]struct{})
}

// checkMark checks that no stale uids remain marked
func (store *MessageStore) checkMark() {
	for mark := range store.marked {
		present := false
		for _, uid := range store.uids {
			if mark == uid {
				present = true
				break
			}
		}
		if !present {
			delete(store.marked, mark)
		}
	}
}

// IsMarked checks whether a MessageInfo has been marked
func (store *MessageStore) IsMarked(uid uint32) bool {
	_, marked := store.marked[uid]
	return marked
}

// ToggleVisualMark enters or leaves the visual marking mode
func (store *MessageStore) ToggleVisualMark() {
	store.visualMarkMode = !store.visualMarkMode
	switch store.visualMarkMode {
	case true:
		// just entered visual mode, reset whatever marking was already done
		store.resetMark()
		store.visualStartUid = store.Selected().Uid
		store.marked[store.visualStartUid] = struct{}{}
	case false:
		// visual mode ended, nothing to do
		return
	}
}

// ClearVisualMark leaves the visual marking mode and resets any marking
func (store *MessageStore) ClearVisualMark() {
	store.resetMark()
	store.visualMarkMode = false
	store.visualStartUid = 0
}

// Marked returns the uids of all marked messages
func (store *MessageStore) Marked() []uint32 {
	marked := make([]uint32, len(store.marked))
	i := 0
	for uid := range store.marked {
		marked[i] = uid
		i++
	}
	return marked
}

func (store *MessageStore) updateVisual() {
	if !store.visualMarkMode {
		// nothing to do
		return
	}
	startIdx := store.visualStartIdx()
	if startIdx < 0 {
		// something deleted the startuid, abort the marking process
		store.ClearVisualMark()
		return
	}

	selectedIdx := store.FindIndexByUid(store.SelectedUid())
	if selectedIdx < 0 {
		store.ClearVisualMark()
		return
	}

	var visUids []uint32
	if selectedIdx > startIdx {
		visUids = store.Uids()[startIdx : selectedIdx+1]
	} else {
		visUids = store.Uids()[selectedIdx : startIdx+1]
	}

	store.resetMark()
	for _, uid := range visUids {
		store.marked[uid] = struct{}{}
	}
	missing := make([]uint32, 0)
	for _, uid := range visUids {
		if msg := store.Messages[uid]; msg == nil {
			missing = append(missing, uid)
		}
	}
	store.FetchHeaders(missing, nil)
}

func (store *MessageStore) NextPrev(delta int) {
	uids := store.Uids()
	if len(uids) == 0 {
		return
	}

	uid := store.SelectedUid()

	newIdx := store.FindIndexByUid(uid)
	if newIdx < 0 {
		store.Select(uids[len(uids)-1])
		return
	}

	newIdx -= delta
	if newIdx >= len(uids) {
		newIdx = len(uids) - 1
	} else if newIdx < 0 {
		newIdx = 0
	}

	store.Select(uids[newIdx])

	store.updateVisual()

	nextResultIndex := len(store.results) - store.resultIndex - 2*delta
	if nextResultIndex < 0 || nextResultIndex >= len(store.results) {
		return
	}
	nextResultUid := store.results[nextResultIndex]
	if nextResultUid == store.SelectedUid() {
		store.resultIndex += delta
	}
}

func (store *MessageStore) Next() {
	store.NextPrev(1)
}

func (store *MessageStore) Prev() {
	store.NextPrev(-1)
}

func (store *MessageStore) Search(args []string, cb func([]uint32)) {
	store.worker.PostAction(&types.SearchDirectory{
		Argv: args,
	}, func(msg types.WorkerMessage) {
		switch msg := msg.(type) {
		case *types.SearchResults:
			allowedUids := store.Uids()
			uids := make([]uint32, 0, len(msg.Uids))
			for _, uid := range msg.Uids {
				for _, uidCheck := range allowedUids {
					if uid == uidCheck {
						uids = append(uids, uid)
						break
					}
				}
			}
			sort.SortBy(uids, allowedUids)
			cb(uids)
		}
	})
}

func (store *MessageStore) ApplySearch(results []uint32) {
	store.results = results
	store.resultIndex = -1
	store.NextResult()
}

func (store *MessageStore) SetFilter(args []string) {
	store.filter = append(store.filter, args...)
}

func (store *MessageStore) ApplyClear() {
	store.filter = []string{"filter"}
	store.results = nil
	if store.onFilterChange != nil {
		store.onFilterChange(store)
	}
	store.Sort(nil, nil)
}

func (store *MessageStore) nextPrevResult(delta int) {
	if len(store.results) == 0 {
		return
	}
	store.resultIndex += delta
	if store.resultIndex >= len(store.results) {
		store.resultIndex = 0
	}
	if store.resultIndex < 0 {
		store.resultIndex = len(store.results) - 1
	}
	store.Select(store.results[len(store.results)-store.resultIndex-1])
	store.update()
}

func (store *MessageStore) NextResult() {
	store.nextPrevResult(1)
}

func (store *MessageStore) PrevResult() {
	store.nextPrevResult(-1)
}

func (store *MessageStore) ModifyLabels(uids []uint32, add, remove []string,
	cb func(msg types.WorkerMessage),
) {
	store.worker.PostAction(&types.ModifyLabels{
		Uids:   uids,
		Add:    add,
		Remove: remove,
	}, cb)
}

func (store *MessageStore) Sort(criteria []*types.SortCriterion, cb func(types.WorkerMessage)) {
	store.sortCriteria = criteria
	store.Sorting = true

	handle_return := func(msg types.WorkerMessage) {
		store.Sorting = false
		if cb != nil {
			cb(msg)
		}
	}

	if store.threadedView && !store.buildThreads {
		store.worker.PostAction(&types.FetchDirectoryThreaded{
			SortCriteria:   criteria,
			FilterCriteria: store.filter,
		}, handle_return)
	} else {
		store.worker.PostAction(&types.FetchDirectoryContents{
			SortCriteria:   criteria,
			FilterCriteria: store.filter,
		}, handle_return)
	}
}

func (store *MessageStore) GetCurrentSortCriteria() []*types.SortCriterion {
	return store.sortCriteria
}

// returns the index of needle in haystack or -1 if not found
func (store *MessageStore) visualStartIdx() int {
	for idx, u := range store.Uids() {
		if u == store.visualStartUid {
			return idx
		}
	}
	return -1
}

// FindIndexByUid returns the index in store.Uids() or -1 if not found
func (store *MessageStore) FindIndexByUid(uid uint32) int {
	for idx, u := range store.Uids() {
		if u == uid {
			return idx
		}
	}
	return -1
}

// Capabilities returns a models.Capabilities struct or nil if not available
func (store *MessageStore) Capabilities() *models.Capabilities {
	return store.DirInfo.Caps
}