package main

// jobs.go is the same file in the bundles whose acts can outlast one call (flatpak, docker-compose):
// an install or an `up` that pulls images takes minutes, and the runtime gives a call 30 s. Such an
// act is started as a job inside this process, waited on for a while, and answered either finished
// or with the job's id for the module's `_job` tool to follow. A job ends with this process: if the
// runtime restarts the bundle, a running job is cut off, and its id is then unknown.

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

// JobLimit is the longest a job may run; JobWait how long an act waits before answering a job id.
const (
	JobLimit = 15 * time.Minute
	JobWait  = 18 * time.Second
	keptJobs = 50
)

// Job is one long act, as its tool answers it.
type Job struct {
	ID        string     `json:"job"`
	Command   string     `json:"command"`
	Started   time.Time  `json:"started"`
	Finished  *time.Time `json:"finished,omitempty"`
	Running   bool       `json:"running"`
	Status    *int       `json:"status,omitempty"`
	Error     string     `json:"error,omitempty"`
	Output    string     `json:"output,omitempty"`
	Truncated bool       `json:"truncated,omitempty"`
	done      chan struct{}
}

type jobBook struct {
	mu   sync.Mutex
	seq  int
	jobs map[string]*Job
}

var jobs = &jobBook{jobs: map[string]*Job{}}

// startJob runs c in the background, held to JobLimit.
func startJob(c Cmd) *Job {
	c.Timeout = JobLimit
	name, args := argv(c)
	jobs.mu.Lock()
	jobs.seq++
	j := &Job{ID: fmt.Sprintf("%d-%d", time.Now().Unix(), jobs.seq), Command: strings.TrimSpace(name + " " + strings.Join(args, " ")),
		Started: time.Now().UTC(), Running: true, done: make(chan struct{})}
	jobs.jobs[j.ID] = j
	jobs.forgetOldest()
	jobs.mu.Unlock()
	go func() {
		r := run(c)
		var err error
		if r.Status != 0 || r.Error != "" {
			err = failure(c, r)
		}
		jobs.mu.Lock()
		now := time.Now().UTC()
		j.Finished, j.Running = &now, false
		status := r.Status
		j.Status = &status
		if err != nil {
			j.Error = err.Error()
		}
		j.Output = tail(strings.TrimSpace(r.Stdout+"\n"+r.Stderr), 16<<10)
		j.Truncated = r.Truncated || len(r.Stdout)+len(r.Stderr) > 16<<10
		jobs.mu.Unlock()
		close(j.done)
	}()
	return j
}

// forgetOldest keeps the book bounded; finished jobs go first. Called with the lock held.
func (b *jobBook) forgetOldest() {
	if len(b.jobs) <= keptJobs {
		return
	}
	all := make([]*Job, 0, len(b.jobs))
	for _, j := range b.jobs {
		all = append(all, j)
	}
	sort.Slice(all, func(i, k int) bool { return all[i].Started.Before(all[k].Started) })
	for _, j := range all {
		if len(b.jobs) <= keptJobs {
			return
		}
		if !j.Running {
			delete(b.jobs, j.ID)
		}
	}
}

// awaitJob waits up to d for a job to finish and answers a copy of it as it then stands.
func awaitJob(j *Job, d time.Duration) Job {
	select {
	case <-j.done:
	case <-time.After(d):
	}
	return snapshot(j)
}

func snapshot(j *Job) Job {
	jobs.mu.Lock()
	defer jobs.mu.Unlock()
	c := *j
	c.done = nil
	return c
}

// jobByID answers a job by its id, or says it is not known to this process.
func jobByID(id string) (Job, error) {
	jobs.mu.Lock()
	j, ok := jobs.jobs[id]
	jobs.mu.Unlock()
	if !ok {
		return Job{}, fmt.Errorf("no job %s in this process: it was never started here, was forgotten after %d newer ones, or the bundle has restarted since", id, keptJobs)
	}
	return snapshot(j), nil
}

// listJobs answers every job this process knows, newest first.
func listJobs() []Job {
	jobs.mu.Lock()
	all := make([]*Job, 0, len(jobs.jobs))
	for _, j := range jobs.jobs {
		all = append(all, j)
	}
	jobs.mu.Unlock()
	sort.Slice(all, func(i, k int) bool { return all[i].Started.After(all[k].Started) })
	out := make([]Job, 0, len(all))
	for _, j := range all {
		out = append(out, snapshot(j))
	}
	return out
}

// actAsJob starts c and answers the job once it finishes or JobWait passes, whichever is first.
// A finished job that failed is answered as an error, so a failed act is never read as success.
func actAsJob(c Cmd) (Job, error) {
	j := awaitJob(startJob(c), JobWait)
	if !j.Running && j.Error != "" {
		return j, fmt.Errorf("%s (job %s)", j.Error, j.ID)
	}
	return j, nil
}