// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package vc

import (
	"fmt"
	"sync"

	"v.io/x/ref/runtime/internal/rpc/stream"

	"v.io/v23/naming"
	"v.io/v23/verror"
)

var errXVCCacheClosed = reg(".errXVCCacheClosed", "vc cache has been closed")

// XVCCache implements a set of VIFs keyed by the endpoint of the remote end and the
// local principal. Multiple goroutines can invoke methods on the XVCCache simultaneously.
type XVCCache struct {
	mu       sync.Mutex
	epCache  map[string]*xvc           // GUARDED_BY(mu)
	ridCache map[naming.RoutingID]*xvc // GUARDED_BY(mu)
	started  map[string]bool           // GUARDED_BY(mu)
	cond     *sync.Cond
}

// NewXVCCache returns a new cache for XVCs.
func NewXVCCache() *XVCCache {
	c := &XVCCache{
		epCache:  make(map[string]*xvc),
		ridCache: make(map[naming.RoutingID]*xvc),
		started:  make(map[string]bool),
	}
	c.cond = sync.NewCond(&c.mu)
	return c
}

// ReservedFind returns a XVC where the remote end of the underlying connection
// is identified by the provided (ep). Returns nil if there is no
// such XVC.
//
// Iff the cache is closed, ReservedFind will return an error.
// If ReservedFind has no error, the caller is required to call Unreserve, to avoid deadlock.
// The ep in Unreserve must be the same as the one used in the ReservedFind call.
// During this time, all new ReservedFind calls for this ep will Block until
// the corresponding Unreserve call is made.
func (c *XVCCache) ReservedFind(ep naming.Endpoint) (stream.XVC, error) {
	if ret, ok := c.ridCache[ep.RoutingID()]; ok {
		return ret, nil
	}
	k := ep.String()
	c.mu.Lock()
	defer c.mu.Unlock()
	for c.started[k] {
		c.cond.Wait()
	}
	if c.epCache == nil {
		return nil, verror.New(errXVCCacheClosed, nil)
	}
	c.started[k] = true
	ret := c.epCache[k]
	if ret == nil {
		return nil, nil
	}
	return ret, nil
}

// Unreserve marks the status of the ep as no longer started, and
// broadcasts waiting threads.
func (c *XVCCache) Unreserve(ep naming.Endpoint) {
	c.mu.Lock()
	delete(c.started, ep.String())
	c.cond.Broadcast()
	c.mu.Unlock()
}

// Insert adds vc to the cache and returns an error iff the cache has been closed.
func (c *XVCCache) Insert(v stream.XVC) error {
	vc, ok := v.(*xvc)
	if !ok {
		return fmt.Errorf("vc %#v is not of type *vc.xvc", vc)
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.epCache == nil {
		return verror.New(errXVCCacheClosed, nil)
	}
	c.epCache[vc.RemoteEndpoint().String()] = vc
	c.ridCache[vc.RemoteEndpoint().RoutingID()] = vc
	return nil
}

// Close marks the XVCCache as closed and returns the XVCs remaining in the cache.
func (c *XVCCache) Close() []*xvc {
	c.mu.Lock()
	vcs := make([]*xvc, 0, len(c.epCache))
	for _, vc := range c.epCache {
		vcs = append(vcs, vc)
	}
	c.epCache = nil
	c.ridCache = nil
	c.started = nil
	c.mu.Unlock()
	return vcs
}

// Delete removes vc from the cache, returning an error iff the cache has been closed.
func (c *XVCCache) Delete(vc *xvc) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.epCache == nil {
		return verror.New(errXVCCacheClosed, nil)
	}
	delete(c.epCache, vc.RemoteEndpoint().String())
	delete(c.ridCache, vc.RemoteEndpoint().RoutingID())
	return nil
}