// Licensed to the LF AI & Data foundation under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package flowgraph

import (
	"context"
	"errors"
	"sync"
)

// TimeTickedFlowGraph flowgraph with input from tt msg stream
type TimeTickedFlowGraph struct {
	nodeCtx   map[NodeName]*nodeCtx
	stopOnce  sync.Once
	startOnce sync.Once
	closeWg   *sync.WaitGroup
}

// AddNode add Node into flowgraph
func (fg *TimeTickedFlowGraph) AddNode(node Node) {
	nodeCtx := nodeCtx{
		node:                   node,
		downstreamInputChanIdx: make(map[string]int),
		closeCh:                make(chan struct{}),
		closeWg:                fg.closeWg,
	}
	fg.nodeCtx[node.Name()] = &nodeCtx
}

// SetEdges set directed edges from in nodes to out nodes
func (fg *TimeTickedFlowGraph) SetEdges(nodeName string, in []string, out []string) error {
	currentNode, ok := fg.nodeCtx[nodeName]
	if !ok {
		errMsg := "Cannot find node:" + nodeName
		return errors.New(errMsg)
	}

	// init current node's downstream
	currentNode.downstream = make([]*nodeCtx, len(out))

	// set in nodes
	for i, inNodeName := range in {
		inNode, ok := fg.nodeCtx[inNodeName]
		if !ok {
			errMsg := "Cannot find in node:" + inNodeName
			return errors.New(errMsg)
		}
		inNode.downstreamInputChanIdx[nodeName] = i
	}

	// set out nodes
	for i, n := range out {
		outNode, ok := fg.nodeCtx[n]
		if !ok {
			errMsg := "Cannot find out node:" + n
			return errors.New(errMsg)
		}
		maxQueueLength := outNode.node.MaxQueueLength()
		outNode.inputChannels = append(outNode.inputChannels, make(chan Msg, maxQueueLength))
		currentNode.downstream[i] = outNode
	}

	return nil
}

// Start starts all nodes in timetick flowgragh
func (fg *TimeTickedFlowGraph) Start() {
	fg.startOnce.Do(func() {
		for _, v := range fg.nodeCtx {
			v.Start()
		}
	})
}

// Close closes all nodes in flowgraph
func (fg *TimeTickedFlowGraph) Close() {
	fg.stopOnce.Do(func() {
		for _, v := range fg.nodeCtx {
			if v.node.IsInputNode() {
				v.Close()
			}
		}
		fg.closeWg.Wait()
	})
}

// NewTimeTickedFlowGraph create timetick flowgraph
func NewTimeTickedFlowGraph(ctx context.Context) *TimeTickedFlowGraph {
	flowGraph := TimeTickedFlowGraph{
		nodeCtx: make(map[string]*nodeCtx),
		closeWg: &sync.WaitGroup{},
	}

	return &flowGraph
}