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// Copyright 2020 CUE Authors
//
// Licensed 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 flow
import (
"fmt"
"strings"
"cuelang.org/go/cue"
"cuelang.org/go/cue/errors"
"cuelang.org/go/cue/token"
)
// checkCycle checks for cyclic dependencies between tasks.
func checkCycle(a []*Task) errors.Error {
cc := cycleChecker{
visited: make([]bool, len(a)),
stack: make([]*Task, 0, len(a)),
}
for _, t := range a {
if cc.isCyclic(t) {
break
}
}
return cc.err
}
type cycleChecker struct {
visited []bool
stack []*Task
err errors.Error
}
func (cc *cycleChecker) isCyclic(t *Task) bool {
i := t.index
if !cc.visited[i] {
cc.visited[i] = true
cc.stack = append(cc.stack, t)
for _, d := range t.depTasks {
if !cc.visited[d.index] && cc.isCyclic(d) {
return true
} else if cc.visited[d.index] {
cc.addCycleError(t)
return true
}
}
}
cc.stack = cc.stack[:len(cc.stack)-1]
cc.visited[i] = false
return false
}
func (cc *cycleChecker) addCycleError(start *Task) {
err := &cycleError{}
for _, t := range cc.stack {
err.path = append(err.path, t.v.Path())
err.positions = append(err.positions, t.v.Pos())
}
cc.err = errors.Append(cc.err, err)
}
type cycleError struct {
path []cue.Path
positions []token.Pos
}
func (e *cycleError) Error() string {
msg, args := e.Msg()
return fmt.Sprintf(msg, args...)
}
func (e *cycleError) Path() []string { return nil }
func (e *cycleError) Msg() (format string, args []interface{}) {
w := &strings.Builder{}
for _, p := range e.path {
fmt.Fprintf(w, "\n\ttask %s refers to", p)
}
fmt.Fprintf(w, "\n\ttask %s", e.path[0])
return "cyclic task dependency:%v", []interface{}{w.String()}
}
func (e *cycleError) Position() token.Pos {
if len(e.positions) == 0 {
return token.NoPos
}
return e.positions[0]
}
func (e *cycleError) InputPositions() []token.Pos {
return e.positions
}
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