// MIT License

// Copyright (c) 2018 Andy Pan

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package ants

import (
	"errors"
	"math"
	"runtime"
	"time"
)

const (
	// DefaultAntsPoolSize is the default capacity for a default goroutine pool.
	DefaultAntsPoolSize = math.MaxInt32

	// DefaultCleanIntervalTime is the interval time to clean up goroutines.
	DefaultCleanIntervalTime = time.Second

	// CLOSED represents that the pool is closed.
	CLOSED = 1
)

var (
	// Error types for the Ants API.
	//---------------------------------------------------------------------------

	// ErrInvalidPoolSize will be returned when setting a negative number as pool capacity.
	ErrInvalidPoolSize = errors.New("invalid size for pool")

	// ErrLackPoolFunc will be returned when invokers don't provide function for pool.
	ErrLackPoolFunc = errors.New("must provide function for pool")

	// ErrInvalidPoolExpiry will be returned when setting a negative number as the periodic duration to purge goroutines.
	ErrInvalidPoolExpiry = errors.New("invalid expiry for pool")

	// ErrPoolClosed will be returned when submitting task to a closed pool.
	ErrPoolClosed = errors.New("this pool has been closed")

	// ErrPoolOverload will be returned when the pool is full and no workers available.
	ErrPoolOverload = errors.New("too many goroutines blocked on submit or Nonblocking is set")
	//---------------------------------------------------------------------------

	// workerChanCap determines whether the channel of a worker should be a buffered channel
	// to get the best performance. Inspired by fasthttp at https://github.com/valyala/fasthttp/blob/master/workerpool.go#L139
	workerChanCap = func() int {
		// Use blocking workerChan if GOMAXPROCS=1.
		// This immediately switches Serve to WorkerFunc, which results
		// in higher performance (under go1.5 at least).
		if runtime.GOMAXPROCS(0) == 1 {
			return 0
		}

		// Use non-blocking workerChan if GOMAXPROCS>1,
		// since otherwise the Serve caller (Acceptor) may lag accepting
		// new connections if WorkerFunc is CPU-bound.
		return 1
	}()

	// Init a instance pool when importing ants.
	defaultAntsPool, _ = NewPool(DefaultAntsPoolSize)
)

// Option represents the optional function.
type Option func(opts *Options)

// Options contains all options which will be applied when instantiating a ants pool.
type Options struct {
	// ExpiryDuration set the expired time of every worker.
	ExpiryDuration time.Duration

	// PreAlloc indicate whether to make memory pre-allocation when initializing Pool.
	PreAlloc bool

	// Max number of goroutine blocking on pool.Submit.
	// 0 (default value) means no such limit.
	MaxBlockingTasks int

	// When Nonblocking is true, Pool.Submit will never be blocked.
	// ErrPoolOverload will be returned when Pool.Submit cannot be done at once.
	// When Nonblocking is true, MaxBlockingTasks is inoperative.
	Nonblocking bool

	// PanicHandler is used to handle panics from each worker goroutine.
	// if nil, panics will be thrown out again from worker goroutines.
	PanicHandler func(interface{})
}

// WithOptions accepts the whole options config.
func WithOptions(options Options) Option {
	return func(opts *Options) {
		*opts = options
	}
}

// WithExpiryDuration sets up the interval time of cleaning up goroutines.
func WithExpiryDuration(expiryDuration time.Duration) Option {
	return func(opts *Options) {
		opts.ExpiryDuration = expiryDuration
	}
}

// WithPreAlloc indicates whether it should malloc for workers.
func WithPreAlloc(preAlloc bool) Option {
	return func(opts *Options) {
		opts.PreAlloc = preAlloc
	}
}

// WithMaxBlockingTasks sets up the maximum number of goroutines that are blocked when it reaches the capacity of pool.
func WithMaxBlockingTasks(maxBlockingTasks int) Option {
	return func(opts *Options) {
		opts.MaxBlockingTasks = maxBlockingTasks
	}
}

// WithNonblocking indicates that pool will return nil when there is no available workers.
func WithNonblocking(nonblocking bool) Option {
	return func(opts *Options) {
		opts.Nonblocking = nonblocking
	}
}

// WithPanicHandler sets up panic handler.
func WithPanicHandler(panicHandler func(interface{})) Option {
	return func(opts *Options) {
		opts.PanicHandler = panicHandler
	}
}

// Submit submits a task to pool.
func Submit(task func()) error {
	return defaultAntsPool.Submit(task)
}

// Running returns the number of the currently running goroutines.
func Running() int {
	return defaultAntsPool.Running()
}

// Cap returns the capacity of this default pool.
func Cap() int {
	return defaultAntsPool.Cap()
}

// Free returns the available goroutines to work.
func Free() int {
	return defaultAntsPool.Free()
}

// Release Closes the default pool.
func Release() {
	defaultAntsPool.Release()
}