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package completer
import (
"bufio"
"errors"
"fmt"
"io"
"mime"
"net/mail"
"os/exec"
"regexp"
"strings"
"github.com/google/shlex"
)
// A Completer is used to autocomplete text inputs based on the configured
// completion commands.
type Completer struct {
// AddressBookCmd is the command to run for completing email addresses. This
// command must output one completion on each line with fields separated by a
// tab character. The first field must be the address, and the second field,
// if present, the contact name. Only the email address field is required.
// The name field is optional. Additional fields are ignored.
AddressBookCmd string
errHandler func(error)
}
// A CompleteFunc accepts a string to be completed and returns a slice of
// completions candidates with a prefix to prepend to the chosen candidate
type CompleteFunc func(string) ([]string, string)
// New creates a new Completer with the specified address book command.
func New(addressBookCmd string, errHandler func(error)) *Completer {
return &Completer{
AddressBookCmd: addressBookCmd,
errHandler: errHandler,
}
}
// ForHeader returns a CompleteFunc appropriate for the specified mail header. In
// the case of To, From, etc., the completer will get completions from the
// configured address book command. For other headers, a noop completer will be
// returned. If errors arise during completion, the errHandler will be called.
func (c *Completer) ForHeader(h string) CompleteFunc {
if isAddressHeader(h) {
if c.AddressBookCmd == "" {
return nil
}
// wrap completeAddress in an error handler
return func(s string) ([]string, string) {
completions, prefix, err := c.completeAddress(s)
if err != nil {
c.handleErr(err)
return []string{}, ""
}
return completions, prefix
}
}
return nil
}
// isAddressHeader determines whether the address completer should be used for
// header h.
func isAddressHeader(h string) bool {
switch strings.ToLower(h) {
case "to", "from", "cc", "bcc":
return true
}
return false
}
// completeAddress uses the configured address book completion command to fetch
// completions for the specified string, returning a slice of completions and
// a prefix to be prepended to the selected completion, or an error.
func (c *Completer) completeAddress(s string) ([]string, string, error) {
prefix, candidate := c.parseAddress(s)
cmd, err := c.getAddressCmd(candidate)
if err != nil {
return nil, "", err
}
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, "", fmt.Errorf("stdout: %w", err)
}
stderr, err := cmd.StderrPipe()
if err != nil {
return nil, "", fmt.Errorf("stderr: %w", err)
}
if err := cmd.Start(); err != nil {
return nil, "", fmt.Errorf("cmd start: %w", err)
}
// Wait returns an error if the exit status != 0, which some completion
// programs will do to signal no matches. We don't want to spam the user with
// spurious error messages, so we'll ignore any errors that arise at this
// point.
defer cmd.Wait() //nolint:errcheck // see above
completions, err := readCompletions(stdout)
if err != nil {
buf, _ := io.ReadAll(stderr)
msg := strings.TrimSpace(string(buf))
if msg != "" {
msg = ": " + msg
}
return nil, "", fmt.Errorf("read completions%s: %w", msg, err)
}
return completions, prefix, nil
}
// parseAddress will break an address header into a prefix (containing
// the already valid addresses) and an input for completion
func (c *Completer) parseAddress(s string) (string, string) {
pattern := regexp.MustCompile(`^(.*),\s+([^,]*)$`)
matches := pattern.FindStringSubmatch(s)
if matches == nil {
return "", s
}
return matches[1] + ", ", matches[2]
}
// getAddressCmd constructs an exec.Cmd based on the configured command and
// specified query.
func (c *Completer) getAddressCmd(s string) (*exec.Cmd, error) {
if strings.TrimSpace(c.AddressBookCmd) == "" {
return nil, fmt.Errorf("no command configured")
}
queryCmd := strings.ReplaceAll(c.AddressBookCmd, "%s", s)
parts, err := shlex.Split(queryCmd)
if err != nil {
return nil, fmt.Errorf("could not lex command")
}
if len(parts) < 1 {
return nil, fmt.Errorf("empty command")
}
if len(parts) > 1 {
return exec.Command(parts[0], parts[1:]...), nil
}
return exec.Command(parts[0]), nil
}
// readCompletions reads a slice of completions from r line by line. Each line
// must consist of tab-delimited fields. Only the first field (the email
// address field) is required, the second field (the contact name) is optional,
// and subsequent fields are ignored.
func readCompletions(r io.Reader) ([]string, error) {
buf := bufio.NewReader(r)
completions := []string{}
for {
line, err := buf.ReadString('\n')
if errors.Is(err, io.EOF) {
return completions, nil
} else if err != nil {
return nil, err
}
parts := strings.SplitN(line, "\t", 3)
addr, err := mail.ParseAddress(strings.TrimSpace(parts[0]))
if err != nil {
return nil, err
}
if len(parts) > 1 {
addr.Name = strings.TrimSpace(parts[1])
}
decoded, err := decodeMIME(addr.String())
if err != nil {
return nil, fmt.Errorf("could not decode MIME string: %w", err)
}
completions = append(completions, decoded)
}
}
func decodeMIME(s string) (string, error) {
var d mime.WordDecoder
return d.DecodeHeader(s)
}
func (c *Completer) handleErr(err error) {
if c.errHandler != nil {
c.errHandler(err)
}
}
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