Finish implementation of config file parsing

Still needs tests

tools/cmd/ssh/config.go

@@ -3,8 +3,16 @@
 package ssh
 
 import (
+	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 	"strings"
+
+	"kitty/tools/utils/paths"
+	"kitty/tools/utils/shlex"
+
+	"golang.org/x/sys/unix"
 )
 
 var _ = fmt.Print
@@ -19,9 +27,9 @@ type CopyInstruction struct {
 	exclude_patterns    []string
 }
 
-func NewEnvInstruction(spec string) (ei *EnvInstruction, err error) {
+func ParseEnvInstruction(spec string) (ans []*EnvInstruction, err error) {
 	const COPY_FROM_LOCAL string = "_kitty_copy_env_var_"
-	ei = &EnvInstruction{}
+	ei := &EnvInstruction{}
 	found := false
 	ei.key, ei.val, found = strings.Cut(spec, "=")
 	ei.key = strings.TrimSpace(ei.key)
@@ -37,10 +45,98 @@ func NewEnvInstruction(spec string) (ei *EnvInstruction, err error) {
 	if ei.key == "" {
 		err = fmt.Errorf("The env directive must not be empty")
 	}
+	ans = []*EnvInstruction{ei}
 	return
 }
 
-func NewCopyInstruction(spec string) (ci *CopyInstruction, err error) {
-	ci = &CopyInstruction{}
+var paths_ctx *paths.Ctx
+
+func resolve_file_spec(spec string, is_glob bool) ([]string, error) {
+	if paths_ctx == nil {
+		paths_ctx = &paths.Ctx{}
+	}
+	ans := os.ExpandEnv(paths_ctx.ExpandHome(spec))
+	if !filepath.IsAbs(ans) {
+		ans = paths_ctx.AbspathFromHome(ans)
+	}
+	if is_glob {
+		files, err := filepath.Glob(ans)
+		if err != nil {
+			return nil, err
+		}
+		if len(files) == 0 {
+			return nil, fmt.Errorf("%s does not exist", spec)
+		}
+		return files, nil
+	}
+	err := unix.Access(ans, unix.R_OK)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, fmt.Errorf("%s does not exist", spec)
+		}
+		return nil, fmt.Errorf("Cannot read from: %s with error: %w", spec, err)
+	}
+	return []string{ans}, nil
+}
+
+func get_arcname(loc, dest, home string) (arcname string) {
+	if dest != "" {
+		arcname = dest
+	} else {
+		arcname = filepath.Clean(loc)
+		if filepath.HasPrefix(arcname, home) {
+			ra, err := filepath.Rel(home, arcname)
+			if err == nil {
+				arcname = ra
+			}
+		}
+	}
+	prefix := "home/"
+	if strings.HasPrefix(arcname, "/") {
+		prefix = "root"
+	}
+	return prefix + arcname
+}
+
+func ParseCopyInstruction(spec string) (ans []*CopyInstruction, err error) {
+	args, err := shlex.Split(spec)
+	if err != nil {
+		return nil, err
+	}
+	opts, args, err := parse_copy_args(args)
+	if err != nil {
+		return nil, err
+	}
+	locations := make([]string, 0, len(args))
+	for _, arg := range args {
+		locs, err := resolve_file_spec(arg, opts.Glob)
+		if err != nil {
+			return nil, err
+		}
+		locations = append(locations, locs...)
+	}
+	if len(locations) == 0 {
+		return nil, fmt.Errorf("No files to copy specified")
+	}
+	if len(locations) > 1 && opts.Dest != "" {
+		return nil, fmt.Errorf("Specifying a remote location with more than one file is not supported")
+	}
+	home := paths_ctx.HomePath()
+	ans = make([]*CopyInstruction, 0, len(locations))
+	for _, loc := range locations {
+		ci := CopyInstruction{local_path: loc, exclude_patterns: opts.Exclude}
+		if opts.SymlinkStrategy != "preserve" {
+			ci.local_path, err = filepath.EvalSymlinks(loc)
+			if err != nil {
+				return nil, fmt.Errorf("Failed to resolve symlinks in %#v with error: %w", loc, err)
+			}
+		}
+		if opts.SymlinkStrategy == "resolve" {
+			ci.arcname = get_arcname(ci.local_path, opts.Dest, home)
+		} else {
+			ci.arcname = get_arcname(loc, opts.Dest, home)
+		}
+		ans = append(ans, &ci)
+	}
 	return
 }