-n command line argument and n query string param

mikebd · Oct 6, 2023 · 60b94f9 · 60b94f9
1 parent 8818188
commit 60b94f9
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Showing 9 changed files with 78 additions and 11 deletions.
diff --git a/README.md b/README.md
@@ -53,8 +53,9 @@ are naturally in `/var/log`.
 
 ## Arguments
 
-| Argument         | Description                           |
-|------------------|---------------------------------------|
-| `-h` \| `--help` | Print the help message                |
-| `-lt`            | Log with timestamps (UTC)             |
-| `-p`             | HTTP Port to listen on (default 8080) |
+| Argument         | Description                            |
+|------------------|----------------------------------------|
+| `-h` \| `--help` | Print the help message                 |
+| `-lt`            | Log with timestamps (UTC)              |
+| `-n`             | Number of lines to return (default 25) |
+| `-p`             | HTTP Port to listen on (default 8080)  |
diff --git a/config/arguments.go b/config/arguments.go
@@ -5,15 +5,18 @@ import (
 )
 
 type Arguments struct {
-	HttpPort      int
-	LogTimestamps bool
+	HttpPort         int
+	LogTimestamps    bool
+	NumberOfLogLines int
 }
 
 func ParseArguments() Arguments {
 	args := Arguments{}
+	configure(&args)
 
 	flag.IntVar(&args.HttpPort, "p", HttpPort, "HTTP port")
 	flag.BoolVar(&args.LogTimestamps, "lt", false, "Log timestamps (UTC)")
+	flag.IntVar(&args.NumberOfLogLines, "n", NumberOfLogLines, "Number of log lines to return")
 	flag.Parse()
 
 	return args

diff --git a/config/constants.go b/config/constants.go
@@ -3,5 +3,6 @@ package config
 const (
 	HttpPort             = 8080
 	LogDirectory         = "/var/log"
+	NumberOfLogLines     = 25
 	UnsupportedFileTypes = "gz|zip|bz2|tar|tgz|7z|rar"
 )
diff --git a/config/inject.go b/config/inject.go
@@ -0,0 +1,13 @@
+package config
+
+// Framework-less "dependency injection" for code paths that are difficult to pass these Arguments to
+
+var arguments *Arguments
+
+func configure(args *Arguments) {
+	arguments = args
+}
+
+func GetArguments() *Arguments {
+	return arguments
+}
diff --git a/controller/rest/v1/logs.go b/controller/rest/v1/logs.go
@@ -1,13 +1,15 @@
 package v1
 
 import (
+	"fmt"
 	"github.com/julienschmidt/httprouter"
 	"go-read-var-log/config"
 	"go-read-var-log/controller/rest/util"
 	"go-read-var-log/service"
 	"log"
 	"net/http"
 	"slices"
+	"strconv"
 )
 
 // GetLogs handles GET /api/v1/logs and returns a list of log files in the log directory
@@ -21,7 +23,21 @@ func GetLogs(w http.ResponseWriter, _ *http.Request, _ httprouter.Params) {
 func GetLog(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
 	log.Println("handling", r.URL.RequestURI())
 	logFilename := p.ByName("log")
-	logEvents, err := service.GetLog(config.LogDirectory, logFilename)
+
+	maxLines := config.GetArguments().NumberOfLogLines
+	maxLinesParam := r.URL.Query().Get("n")
+	if maxLinesParam != "" {
+		intParam, err := strconv.Atoi(maxLinesParam)
+		if err == nil && intParam > 0 {
+			maxLines = intParam
+		} else {
+			util.RenderTextPlain(w, nil, fmt.Errorf("invalid value for parameter 'n': '%s'", maxLinesParam))
+			return
+		}
+	}
+
+	logEvents, err := service.GetLog(config.LogDirectory, logFilename, maxLines)
+
 	slices.Reverse(logEvents)
 	util.RenderTextPlain(w, logEvents, err)
 }
diff --git a/service/getLog.go b/service/getLog.go
@@ -7,7 +7,7 @@ import (
 )
 
 // GetLog returns the contents of a log file
-func GetLog(directoryPath string, filename string) ([]string, error) {
+func GetLog(directoryPath string, filename string, maxLines int) ([]string, error) {
 	filepath := strings.Join([]string{directoryPath, filename}, "/")
 
 	if !validLogFromName(directoryPath, filename) {
@@ -19,5 +19,12 @@ func GetLog(directoryPath string, filename string) ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
-	return strings.Split(string(byteSlice), "\n"), nil
+	result := strings.Split(string(byteSlice), "\n")
+
+	// Restrict output to at most maxLines
+	endIndex := len(result) - 1
+	startIndex := max(0, endIndex-maxLines)
+	result = result[startIndex:endIndex]
+
+	return result, nil
 }
diff --git a/service/getLog_test.go b/service/getLog_test.go
@@ -0,0 +1,25 @@
+package service
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Log output is in natural order at the service layer.
+// Controllers may reverse the order as required by their clients.
+
+func ExampleGetLog_logDir1_10KiB_log() {
+	lines, _ := GetLog("testdata/logDir1", "10KiB.log", 2)
+	fmt.Println(strings.Join(lines, "\n"))
+	// Output:
+	// 2023-10-06T15:18:24.408740Z|info |olaret esanus ivo hey enug tewos ebad it u tuge po elora e iwemat o
+	// 2023-10-06T15:18:24.408762Z|debug|tucev uho e u ela opif ce igodeto hudegor ivosu ehab eaunopi balohan tagused gicefas
+}
+
+func ExampleGetLog_logDir1_1line_log() {
+	// Requesting more lines than available returns all available lines.
+	lines, _ := GetLog("testdata/logDir1", "1line.log", 10)
+	fmt.Println(strings.Join(lines, "\n"))
+	// Output:
+	// 2023-10-06T15:18:24.406350Z|debug|toyeni vate riwehu ato ped afe ral bo h redi esohet sir moyireh nema lidef
+}
diff --git a/service/listLogs_test.go b/service/listLogs_test.go
@@ -7,5 +7,5 @@ import (
 func ExampleListLogs_logDir1() {
 	fmt.Println(ListLogs("testdata/logDir1"))
 	// Output:
-	// [10KiB.log] <nil>
+	// [10KiB.log 1line.log] <nil>
 }
diff --git a/service/testdata/logDir1/1line.log b/service/testdata/logDir1/1line.log
@@ -0,0 +1 @@
+2023-10-06T15:18:24.406350Z|debug|toyeni vate riwehu ato ped afe ral bo h redi esohet sir moyireh nema lidef
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		2023-10-06T15:18:24.406350Z\|debug\|toyeni vate riwehu ato ped afe ral bo h redi esohet sir moyireh nema lidef