package main

import (
	"fmt"
	"sort"
	"sync"
	"time"
)

// JobWaitGroup is like sync.WaitGroup, but keeps track of job status,
// and tracks how long each job took.
type JobWaitGroup struct {
	lock sync.RWMutex
	jobs map[string]time.Duration
	wg   sync.WaitGroup
}

// Do a job.
func (jwg *JobWaitGroup) Do(name string, fn func()) {
	jwg.lock.Lock()
	defer jwg.lock.Unlock()

	if jwg.jobs == nil {
		jwg.jobs = make(map[string]time.Duration)
	}
	if _, dup := jwg.jobs[name]; dup {
		panic(fmt.Sprintf("job %q already exists", name))
	}
	jwg.jobs[name] = -1
	jwg.wg.Add(1)
	start := time.Now()
	go func() {
		defer func() {
			jwg.lock.Lock()
			defer jwg.lock.Unlock()
			jwg.jobs[name] = time.Now().Sub(start)
			jwg.wg.Done()
		}()
		fn()
	}()
}

// Wait for all jobs to finish, and return how long each job took.
func (jwg *JobWaitGroup) Wait() map[string]time.Duration {
	jwg.wg.Wait()
	return jwg.jobs
}

// Status returns the total number of jobs that have been started, and
// a list of still-running jobs.
func (jwg *JobWaitGroup) Status() (int, []string) {
	jwg.lock.RLock()

	n := len(jwg.jobs)
	var jobs []string
	for job, duration := range jwg.jobs {
		if duration < 0 {
			jobs = append(jobs, job)
		}
	}
	defer jwg.lock.RUnlock()
	sort.Strings(jobs)

	return n, jobs
}