cli: pager for reading output (-P/--pager, --no-pager, config pager, $PAGER fallback); v0.3.0

1 files changed, 31 insertions, 9 deletions

diff --git a/internal/cli/cli.go b/internal/cli/cli.go
index 130683c..5ee4a34 100644
--- a/internal/cli/cli.go
+++ b/internal/cli/cli.go
@@ -38,6 +38,8 @@ Flags:
   -g, --lang LANG        traditional lectionary language: pl|en
   -u, --update           harvest sigla maximally to the horizon (idempotent)
   -C, --clean            prune cached readings older than a year
+  -P, --pager            page reading output (like git); default from config
+      --no-pager         never page, even if config sets one
   -v, --version          print the version and exit
   -h, --help             this help
 
@@ -88,7 +90,7 @@ func Run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 		return 2
 	}
 
-	var all, raw, refresh, offline, update, clean bool
+	var all, raw, refresh, offline, update, clean, pagerFlag, noPager bool
 	var bibleVer, compareList, lectionary, lang string
 	var width int
 
@@ -118,6 +120,9 @@ func Run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 	fs.BoolVar(&update, "update", false, "harvest sigla maximally to the horizon")
 	fs.BoolVar(&clean, "C", false, "prune cached readings older than a year")
 	fs.BoolVar(&clean, "clean", false, "prune cached readings older than a year")
+	fs.BoolVar(&pagerFlag, "P", false, "page reading output (like git)")
+	fs.BoolVar(&pagerFlag, "pager", false, "page reading output (like git)")
+	fs.BoolVar(&noPager, "no-pager", false, "never page, even if config sets one")
 
 	if err := fs.Parse(rest); err != nil {
 		return 2
@@ -165,17 +170,34 @@ func Run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 		effWidth = cfg.Width
 	}
 
-	if compareList != "" {
-		return renderCompare(cfg, compareList, date, effAll, raw, effWidth, refresh, stdout, stderr)
+	// An invalid -b must exit 2 before any pager starts -- don't page an
+	// error. When compareList != "", bibleVer is unused (compare wins, as
+	// before) so it's deliberately left unvalidated in that case too.
+	if bibleVer != "" && compareList == "" && !config.ValidVersion(bibleVer) {
+		fmt.Fprintf(stderr, "lectio: unknown version %q (want one of pl, wuj, vul, grb, drb)\n", bibleVer)
+		return 2
 	}
-	if bibleVer != "" {
-		if !config.ValidVersion(bibleVer) {
-			fmt.Fprintf(stderr, "lectio: unknown version %q (want one of pl, wuj, vul, grb, drb)\n", bibleVer)
-			return 2
+
+	out := stdout
+	finish := func() {}
+	if pagerRequested(pagerFlag, noPager, cfg) && isTerminalWriter(stdout) {
+		if o, f, ok := startPager(pagerCommand(cfg), stdout, stderr); ok {
+			out = o
+			finish = f
 		}
-		return fetchAndPrint(cfg, bibleVer, date, effAll, raw, effWidth, refresh, stdout, stderr)
 	}
-	return fetchAndPrint(cfg, cfg.DefaultVersion, date, effAll, raw, effWidth, refresh, stdout, stderr)
+
+	var code int
+	switch {
+	case compareList != "":
+		code = renderCompare(cfg, compareList, date, effAll, raw, effWidth, refresh, out, stderr)
+	case bibleVer != "":
+		code = fetchAndPrint(cfg, bibleVer, date, effAll, raw, effWidth, refresh, out, stderr)
+	default:
+		code = fetchAndPrint(cfg, cfg.DefaultVersion, date, effAll, raw, effWidth, refresh, out, stderr)
+	}
+	finish()
+	return code
 }
 
 // wantsHelp reports whether -h/--help appears anywhere in args.