github.com/kaydxh/golang@v0.0.131/pkg/scheduler/task/validate.go (about)

     1  /*
     2   *Copyright (c) 2022, kaydxh
     3   *
     4   *Permission is hereby granted, free of charge, to any person obtaining a copy
     5   *of this software and associated documentation files (the "Software"), to deal
     6   *in the Software without restriction, including without limitation the rights
     7   *to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     8   *copies of the Software, and to permit persons to whom the Software is
     9   *furnished to do so, subject to the following conditions:
    10   *
    11   *The above copyright notice and this permission notice shall be included in all
    12   *copies or substantial portions of the Software.
    13   *
    14   *THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    15   *IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    16   *FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    17   *AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    18   *LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    19   *OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
    20   *SOFTWARE.
    21   */
    22  package task
    23  
    24  import (
    25  	"errors"
    26  	"reflect"
    27  )
    28  
    29  var (
    30  	ErrTaskNil = errors.New("Task must be not nil")
    31  	// ErrTaskMustBeFunc ...
    32  	ErrTaskMustBeFunc = errors.New("Task must be a func type")
    33  	// ErrTaskReturnsNoValue ...
    34  	ErrTaskReturnsNoValue = errors.New("Task must return at least a single value")
    35  	// ErrLastReturnValueMustBeError ..
    36  	ErrLastReturnValueMustBeError = errors.New("Last return value of a task must be error")
    37  )
    38  
    39  // Validate validates task function using reflection and makes sure
    40  // it has a proper signature. Functions used as tasks must return at least a
    41  // single value and the last return type must be error
    42  func Validate(task *Task) error {
    43  	if task == nil {
    44  		return ErrTaskNil
    45  	}
    46  	v := reflect.ValueOf(task.TaskFunc)
    47  	t := v.Type()
    48  
    49  	// TaskFunc must be a function
    50  	if t.Kind() != reflect.Func {
    51  		return ErrTaskMustBeFunc
    52  	}
    53  
    54  	// TaskFunc must return at least a single value
    55  	if t.NumOut() < 1 {
    56  		return ErrTaskReturnsNoValue
    57  	}
    58  
    59  	// Last return value must be error
    60  	lastReturnType := t.Out(t.NumOut() - 1)
    61  	errorInterface := reflect.TypeOf((*error)(nil)).Elem()
    62  	if !lastReturnType.Implements(errorInterface) {
    63  		return ErrLastReturnValueMustBeError
    64  	}
    65  
    66  	return nil
    67  }