init: pristine aerc 0.20.0 source

commands/history.go

@@ -0,0 +1,140 @@
+package commands
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"sync"
+
+	"git.sr.ht/~rjarry/aerc/lib/log"
+	"git.sr.ht/~rjarry/aerc/lib/xdg"
+)
+
+type cmdHistory struct {
+	// rolling buffer of prior commands
+	//
+	// most recent command is at the end of the list,
+	// least recent is index 0
+	cmdList []string
+
+	// current placement in list
+	current int
+
+	// initialize history storage
+	initHistfile sync.Once
+	histfile     io.ReadWriter
+}
+
+// number of commands to keep in history
+const cmdLimit = 1000
+
+// CmdHistory is the history of executed commands
+var CmdHistory = cmdHistory{}
+
+func (h *cmdHistory) Add(cmd string) {
+	h.initHistfile.Do(h.initialize)
+
+	// if we're at cap, cut off the first element
+	if len(h.cmdList) >= cmdLimit {
+		h.cmdList = h.cmdList[1:]
+	}
+
+	if len(h.cmdList) == 0 || h.cmdList[len(h.cmdList)-1] != cmd {
+		h.cmdList = append(h.cmdList, cmd)
+
+		h.writeHistory()
+	}
+
+	// whenever we add a new command, reset the current
+	// pointer to the "beginning" of the list
+	h.Reset()
+}
+
+// Prev returns the previous command in history.
+// Since the list is reverse-order, this will return elements
+// increasingly towards index 0.
+func (h *cmdHistory) Prev() string {
+	h.initHistfile.Do(h.initialize)
+
+	if h.current <= 0 || len(h.cmdList) == 0 {
+		h.current = -1
+		return "(Already at beginning)"
+	}
+	h.current--
+
+	return h.cmdList[h.current]
+}
+
+// Next returns the next command in history.
+// Since the list is reverse-order, this will return elements
+// increasingly towards index len(cmdList).
+func (h *cmdHistory) Next() string {
+	h.initHistfile.Do(h.initialize)
+
+	if h.current >= len(h.cmdList)-1 || len(h.cmdList) == 0 {
+		h.current = len(h.cmdList)
+		return "(Already at end)"
+	}
+	h.current++
+
+	return h.cmdList[h.current]
+}
+
+// Reset the current pointer to the beginning of history.
+func (h *cmdHistory) Reset() {
+	h.current = len(h.cmdList)
+}
+
+func (h *cmdHistory) initialize() {
+	var err error
+	openFlags := os.O_RDWR | os.O_EXCL
+
+	histPath := xdg.StatePath("aerc", "history")
+	if _, err := os.Stat(histPath); os.IsNotExist(err) {
+		_ = os.MkdirAll(xdg.StatePath("aerc"), 0o700) // caught by OpenFile
+		openFlags |= os.O_CREATE
+	}
+
+	// O_EXCL to make sure that only one aerc writes to the file
+	h.histfile, err = os.OpenFile(
+		histPath,
+		openFlags,
+		0o600,
+	)
+	if err != nil {
+		log.Errorf("failed to open history file: %v", err)
+		// basically mirror the old behavior
+		h.histfile = bytes.NewBuffer([]byte{})
+		return
+	}
+
+	s := bufio.NewScanner(h.histfile)
+
+	for s.Scan() {
+		h.cmdList = append(h.cmdList, s.Text())
+	}
+
+	h.Reset()
+}
+
+func (h *cmdHistory) writeHistory() {
+	if fh, ok := h.histfile.(*os.File); ok {
+		err := fh.Truncate(0)
+		if err != nil {
+			// if we can't delete it, don't break it.
+			return
+		}
+		_, err = fh.Seek(0, io.SeekStart)
+		if err != nil {
+			// if we can't delete it, don't break it.
+			return
+		}
+		for _, entry := range h.cmdList {
+			fmt.Fprintln(fh, entry)
+		}
+
+		fh.Sync() //nolint:errcheck // if your computer can't sync you're in bigger trouble
+	}
+}