Add tail to print and follow a fleet's logs

README.md

@@ -1,10 +1,8 @@
 # Superstack CLI
 
 `superstack` is the command line interface to Superstack: log in, create
-fleets, manage devices, and control who can reach them. It is a single static
-binary for managing Superstack from a terminal.
-
-Streaming logs is not available yet.
+fleets, manage devices, read their logs, and control who can reach them. It is
+a single static binary for managing Superstack from a terminal.
 
 ## Install
 

internal/api/logs.go

@@ -0,0 +1,68 @@
+package api
+
+import (
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+)
+
+type LogEntry struct {
+	Id         int64     `json:"id"`
+	Imei       string    `json:"imei"`
+	Name       *string   `json:"name"`
+	Kind       string    `json:"kind"`
+	Text       string    `json:"text"`
+	ReceivedAt time.Time `json:"received_at"`
+}
+
+type LogsAnswer struct {
+	Logs []LogEntry `json:"logs"`
+	Next int64      `json:"next"`
+}
+
+// A request that failed because the server could not be reached or is not available, so a follower may try again
+type Unavailable struct {
+	Reason string
+}
+
+func (unavailable Unavailable) Error() string {
+	return unavailable.Reason
+}
+
+// query holds last and optionally offset, or after, and any imei values that narrow the fleet
+func FetchLogs(invocation Invocation, fleetID int64, query url.Values) (LogsAnswer, error) {
+	request, err := AuthenticatedRequest(invocation, http.MethodGet,
+		"/fleets/"+strconv.FormatInt(fleetID, 10)+"/logs?"+query.Encode(), nil)
+
+	if err != nil {
+		return LogsAnswer{}, err
+	}
+
+	response, err := invocation.Client.Do(request)
+
+	if err != nil {
+		return LogsAnswer{}, Unavailable{"the server could not be reached, check your internet access"}
+	}
+
+	defer response.Body.Close()
+
+	if response.StatusCode == http.StatusBadGateway || response.StatusCode == http.StatusServiceUnavailable ||
+		response.StatusCode == http.StatusGatewayTimeout {
+		return LogsAnswer{}, Unavailable{ServerError(response).Error()}
+	}
+
+	if response.StatusCode != http.StatusOK {
+		return LogsAnswer{}, ServerError(response)
+	}
+
+	answer := LogsAnswer{}
+
+	err = Decode(response, &answer)
+
+	if err != nil {
+		return LogsAnswer{}, err
+	}
+
+	return answer, nil
+}

internal/tail/tail.go

@@ -0,0 +1,173 @@
+package tail
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/siliconwitchery/superstack-cli/internal/api"
+)
+
+func Tail(invocation api.Invocation, arguments []string) error {
+	positionals := []string{}
+	count := int64(0)
+	offset := int64(0)
+
+	for index := 0; index < len(arguments); index++ {
+		switch arguments[index] {
+		case "-n", "-o":
+			flag := arguments[index]
+
+			if index+1 == len(arguments) {
+				return fmt.Errorf("%s needs a number", flag)
+			}
+
+			index++
+
+			value, err := strconv.ParseInt(arguments[index], 10, 64)
+
+			if flag == "-n" {
+				if err != nil || value < 1 || value > 1000 {
+					return errors.New("-n takes a number of logs from 1 to 1000")
+				}
+
+				count = value
+			} else {
+				if err != nil || value < 1 {
+					return errors.New("-o takes how many of the newest logs to skip, 1 or more")
+				}
+
+				offset = value
+			}
+
+		default:
+			positionals = append(positionals, arguments[index])
+		}
+	}
+
+	if len(positionals) == 0 {
+		return errors.New("tail takes a fleet id, then the IMEIs of the devices to show if not all of them")
+	}
+
+	fleetID, err := strconv.ParseInt(positionals[0], 10, 64)
+
+	if err != nil || fleetID < 1 {
+		return errors.New("the fleet id is the number shown by fleet list")
+	}
+
+	query := url.Values{}
+
+	for _, imei := range positionals[1:] {
+		if len(imei) != 15 || strings.ContainsFunc(imei, func(digit rune) bool { return digit < '0' || digit > '9' }) {
+			return fmt.Errorf("%s is not an IMEI, which is the 15-digit number printed on the device", api.Printable(imei))
+		}
+
+		query.Add("imei", imei)
+	}
+
+	if offset > 0 && count == 0 {
+		return errors.New("-o sits the window back from the newest logs, so it needs -n")
+	}
+
+	// A window of past logs
+	if count > 0 {
+		query.Set("last", strconv.FormatInt(count, 10))
+
+		if offset > 0 {
+			query.Set("offset", strconv.FormatInt(offset, 10))
+		}
+
+		answer, err := api.FetchLogs(invocation, fleetID, query)
+
+		if err != nil {
+			return err
+		}
+
+		for _, entry := range answer.Logs {
+			printLog(invocation.Out, entry)
+		}
+
+		return nil
+	}
+
+	// The newest logs, then follow
+	query.Set("last", "100")
+
+	answer, err := api.FetchLogs(invocation, fleetID, query)
+
+	if err != nil {
+		return err
+	}
+
+	for _, entry := range answer.Logs {
+		printLog(invocation.Out, entry)
+	}
+
+	query.Del("last")
+	cursor := answer.Next
+
+	for {
+		query.Set("after", strconv.FormatInt(cursor, 10))
+
+		answer, err = api.FetchLogs(invocation, fleetID, query)
+
+		var unavailable api.Unavailable
+
+		if errors.As(err, &unavailable) {
+			time.Sleep(time.Second)
+			continue
+		}
+
+		if err != nil {
+			return err
+		}
+
+		for _, entry := range answer.Logs {
+			printLog(invocation.Out, entry)
+		}
+
+		cursor = answer.Next
+	}
+}
+
+func printLog(out io.Writer, entry api.LogEntry) {
+	name := ""
+
+	if entry.Name != nil {
+		name = printableKeepingTabs(*entry.Name)
+	}
+
+	fields := fmt.Sprintf("%s %s %s [%s] ",
+		entry.ReceivedAt.Local().Format("2006-01-02T15:04:05-07:00"), entry.Imei, entry.Kind, name)
+	lines := strings.Split(entry.Text, "\n")
+
+	fmt.Fprintf(out, "%s%s\n", fields, printableKeepingTabs(lines[0]))
+
+	for _, line := range lines[1:] {
+		fmt.Fprintf(out, "%s%s\n", strings.Repeat(" ", utf8.RuneCountInString(fields)), printableKeepingTabs(line))
+	}
+}
+
+func printableKeepingTabs(text string) string {
+	printable := strings.Builder{}
+
+	for index := 0; index < len(text); {
+		character, size := utf8.DecodeRuneInString(text[index:])
+		encoded := text[index : index+size]
+		index += size
+
+		if character == '\t' || (strconv.IsGraphic(character) && !(character == utf8.RuneError && size == 1)) {
+			printable.WriteString(encoded)
+			continue
+		}
+
+		printable.WriteString(api.Printable(encoded))
+	}
+
+	return printable.String()
+}