package command

import (
	"fmt"
	"io"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"github.com/hashicorp/nomad/api"
)

type LogsCommand struct {
	Meta
}

func (l *LogsCommand) Help() string {
	helpText := `
Usage: nomad logs [options] <allocation> <task>

  Streams the stdout/stderr of the given allocation and task.

General Options:

  ` + generalOptionsUsage() + `

Logs Specific Options:

  -stderr
    Display stderr logs.

  -verbose
    Show full information.

  -job <job-id>
    Use a random allocation from the specified job ID.

  -f
    Causes the output to not stop when the end of the logs are reached, but
    rather to wait for additional output.

  -tail
    Show the logs contents with offsets relative to the end of the logs. If no
    offset is given, -n is defaulted to 10.

  -n
    Sets the tail location in best-efforted number of lines relative to the end
    of the logs.

  -c
    Sets the tail location in number of bytes relative to the end of the logs.
  `
	return strings.TrimSpace(helpText)
}

func (l *LogsCommand) Synopsis() string {
	return "Streams the logs of a task."
}

func (l *LogsCommand) Run(args []string) int {
	var verbose, job, tail, stderr, follow bool
	var numLines, numBytes int64

	flags := l.Meta.FlagSet("logs", FlagSetClient)
	flags.Usage = func() { l.Ui.Output(l.Help()) }
	flags.BoolVar(&verbose, "verbose", false, "")
	flags.BoolVar(&job, "job", false, "")
	flags.BoolVar(&tail, "tail", false, "")
	flags.BoolVar(&follow, "f", false, "")
	flags.BoolVar(&stderr, "stderr", false, "")
	flags.Int64Var(&numLines, "n", -1, "")
	flags.Int64Var(&numBytes, "c", -1, "")

	if err := flags.Parse(args); err != nil {
		return 1
	}
	args = flags.Args()

	if numArgs := len(args); numArgs < 1 {
		if job {
			l.Ui.Error("Job ID required. See help:\n")
		} else {
			l.Ui.Error("Allocation ID required. See help:\n")
		}

		l.Ui.Error(l.Help())
		return 1
	} else if numArgs > 2 {
		l.Ui.Error(l.Help())
		return 1
	}

	client, err := l.Meta.Client()
	if err != nil {
		l.Ui.Error(fmt.Sprintf("Error initializing client: %v", err))
		return 1
	}

	// If -job is specified, use random allocation, otherwise use provided allocation
	allocID := args[0]
	if job {
		allocID, err = getRandomJobAlloc(client, args[0])
		if err != nil {
			l.Ui.Error(fmt.Sprintf("Error fetching allocations: %v", err))
			return 1
		}
	}

	// Truncate the id unless full length is requested
	length := shortId
	if verbose {
		length = fullId
	}
	// Query the allocation info
	if len(allocID) == 1 {
		l.Ui.Error(fmt.Sprintf("Alloc ID must contain at least two characters."))
		return 1
	}
	if len(allocID)%2 == 1 {
		// Identifiers must be of even length, so we strip off the last byte
		// to provide a consistent user experience.
		allocID = allocID[:len(allocID)-1]
	}

	allocs, _, err := client.Allocations().PrefixList(allocID)
	if err != nil {
		l.Ui.Error(fmt.Sprintf("Error querying allocation: %v", err))
		return 1
	}
	if len(allocs) == 0 {
		l.Ui.Error(fmt.Sprintf("No allocation(s) with prefix or id %q found", allocID))
		return 1
	}
	if len(allocs) > 1 {
		// Format the allocs
		out := formatAllocListStubs(allocs, verbose, length)
		l.Ui.Output(fmt.Sprintf("Prefix matched multiple allocations\n\n%s", out))
		return 0
	}
	// Prefix lookup matched a single allocation
	alloc, _, err := client.Allocations().Info(allocs[0].ID, nil)
	if err != nil {
		l.Ui.Error(fmt.Sprintf("Error querying allocation: %s", err))
		return 1
	}

	var task string
	if len(args) >= 2 {
		task = args[1]
		if task == "" {
			l.Ui.Error("Task name required")
			return 1
		}

	} else {
		// Try to determine the tasks name from the allocation
		var tasks []*api.Task
		for _, tg := range alloc.Job.TaskGroups {
			if *tg.Name == alloc.TaskGroup {
				if len(tg.Tasks) == 1 {
					task = tg.Tasks[0].Name
					break
				}

				tasks = tg.Tasks
				break
			}
		}

		if task == "" {
			l.Ui.Error(fmt.Sprintf("Allocation %q is running the following tasks:", limit(alloc.ID, length)))
			for _, t := range tasks {
				l.Ui.Error(fmt.Sprintf("  * %s", t.Name))
			}
			l.Ui.Error("\nPlease specify the task.")
			return 1
		}
	}

	logType := "stdout"
	if stderr {
		logType = "stderr"
	}

	// We have a file, output it.
	var r io.ReadCloser
	var readErr error
	if !tail {
		r, readErr = l.followFile(client, alloc, follow, task, logType, api.OriginStart, 0)
		if readErr != nil {
			readErr = fmt.Errorf("Error reading file: %v", readErr)
		}
	} else {
		// Parse the offset
		var offset int64 = defaultTailLines * bytesToLines

		if nLines, nBytes := numLines != -1, numBytes != -1; nLines && nBytes {
			l.Ui.Error("Both -n and -c set")
			return 1
		} else if nLines {
			offset = numLines * bytesToLines
		} else if nBytes {
			offset = numBytes
		} else {
			numLines = defaultTailLines
		}

		r, readErr = l.followFile(client, alloc, follow, task, logType, api.OriginEnd, offset)

		// If numLines is set, wrap the reader
		if numLines != -1 {
			r = NewLineLimitReader(r, int(numLines), int(numLines*bytesToLines), 1*time.Second)
		}

		if readErr != nil {
			readErr = fmt.Errorf("Error tailing file: %v", readErr)
		}
	}

	if readErr != nil {
		l.Ui.Error(readErr.Error())
		return 1
	}

	defer r.Close()
	io.Copy(os.Stdout, r)
	return 0
}

// followFile outputs the contents of the file to stdout relative to the end of
// the file.
func (l *LogsCommand) followFile(client *api.Client, alloc *api.Allocation,
	follow bool, task, logType, origin string, offset int64) (io.ReadCloser, error) {

	cancel := make(chan struct{})
	frames, err := client.AllocFS().Logs(alloc, follow, task, logType, origin, offset, cancel, nil)
	if err != nil {
		return nil, err
	}
	signalCh := make(chan os.Signal, 1)
	signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM)

	// Create a reader
	var r io.ReadCloser
	frameReader := api.NewFrameReader(frames, cancel)
	frameReader.SetUnblockTime(500 * time.Millisecond)
	r = frameReader

	go func() {
		<-signalCh

		// End the streaming
		r.Close()
	}()

	return r, nil
}