Format list output

3 files changed, 78 insertions, 4 deletions

diff --git a/drive/files.go b/drive/files.go
index f1a4b97..b10f2f6 100644
--- a/drive/files.go
+++ b/drive/files.go
@@ -14,9 +14,11 @@ func (self *Drive) List(args ListFilesArgs) {
     fileList, err := self.service.Files.List().PageSize(args.MaxFiles).Q(args.Query).Fields("nextPageToken", "files(id,name,size,createdTime)").Do()
     errorF(err, "Failed listing files: %s\n", err)
 
-    for _, f := range fileList.Files {
-        fmt.Printf("%s %s %d %s\n", f.Id, f.Name, f.Size, f.CreatedTime)
-    }
+    PrintFileList(PrintFileListArgs{
+        Files: fileList.Files,
+        SkipHeader: args.SkipHeader,
+        SizeInBytes: args.SizeInBytes,
+    })
 }
 
 
diff --git a/drive/print.go b/drive/print.go
index 5473690..85d51b4 100644
--- a/drive/print.go
+++ b/drive/print.go
@@ -1,13 +1,36 @@
 package drive
 
 import (
+    "os"
     "fmt"
+    "text/tabwriter"
     "strings"
     "strconv"
+    "unicode/utf8"
     "time"
 )
 
 
+func PrintFileList(args PrintFileListArgs) {
+    w := new(tabwriter.Writer)
+    w.Init(os.Stdout, 0, 0, 3, ' ', 0)
+
+    if !args.SkipHeader {
+        fmt.Fprintln(w, "Id\tName\tSize\tCreated")
+    }
+
+    for _, f := range args.Files {
+        fmt.Fprintf(w, "%s\t%s\t%s\t%s\n",
+            f.Id,
+            truncateString(f.Name, 40),
+            formatSize(f.Size, args.SizeInBytes),
+            formatDatetime(f.CreatedTime),
+        )
+    }
+
+    w.Flush()
+}
+
 func PrintFileInfo(args PrintFileInfoArgs) {
     f := args.File
 
@@ -31,7 +54,6 @@ func PrintFileInfo(args PrintFileInfoArgs) {
     }
 }
 
-
 func formatList(a []string) string {
     return strings.Join(a, ", ")
 }
@@ -67,3 +89,47 @@ func formatDatetime(iso string) string {
     hour, min, sec := local.Clock()
     return fmt.Sprintf("%04d-%02d-%02d %02d:%02d:%02d", year, month, day, hour, min, sec)
 }
+
+// Truncates string to given max length, and inserts ellipsis into
+// the middle of the string to signify that the string has been truncated
+func truncateString(str string, maxRunes int) string {
+    indicator := "..."
+
+    // Number of runes in string
+    runeCount := utf8.RuneCountInString(str)
+
+    // Return input string if length of input string is less than max length
+    // Input string is also returned if max length is less than 9 which is the minmal supported length
+    if runeCount <= maxRunes || maxRunes < 9 {
+        return str
+    }
+
+    // Number of remaining runes to be removed
+    remaining := (runeCount - maxRunes) + utf8.RuneCountInString(indicator)
+
+    var truncated string
+    var skip bool
+
+    for leftOffset, char := range str {
+        rightOffset := runeCount - (leftOffset + remaining)
+
+        // Start skipping chars when the left and right offsets are equal
+        // Or in the case where we wont be able to do an even split: when the left offset is larger than the right offset
+        if leftOffset == rightOffset || (leftOffset > rightOffset && !skip) {
+            skip = true
+            truncated += indicator
+        }
+
+        if skip && remaining > 0 {
+            // Skip char and decrement the remaining skip counter
+            remaining--
+            continue
+        }
+
+        // Add char to result string
+        truncated += string(char)
+    }
+
+    // Return truncated string
+    return truncated
+}
diff --git a/drive/types.go b/drive/types.go
index ecf92a1..296902c 100644
--- a/drive/types.go
+++ b/drive/types.go
@@ -51,6 +51,12 @@ type FileInfoArgs struct {
     SizeInBytes bool
 }
 
+type PrintFileListArgs struct {
+    Files []*drive.File
+    SkipHeader bool
+    SizeInBytes bool
+}
+
 type PrintFileInfoArgs struct {
     File *drive.File
     SizeInBytes bool