all: rewrite the Session and Script using Statement

The idea for rewrite is to separate between local and remote script, so
we can apply environment variables to local script.  We also parse and
validate each statements before being executed to simplify the code.

1 files changed, 146 insertions, 0 deletions

diff --git a/statement.go b/statement.go
new file mode 100644
index 0000000..4838e21
--- /dev/null
+++ b/statement.go
@@ -0,0 +1,146 @@
+// Copyright 2021, Shulhan <ms@kilabit.info>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package awwan
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	libexec "github.com/shuLhan/share/lib/os/exec"
+)
+
+const (
+	statementKindDefault = iota
+	statementKindComment
+	statementKindRequire
+	statementKindGet
+	statementKindPut
+	statementKindSudoGet
+	statementKindSudoPut
+)
+
+//
+// Statetement contains parsed raw line from the script.
+//
+type Statement struct {
+	kind int
+	cmd  string
+	args []string
+	raw  []byte
+}
+
+//
+// ParseStatement create and initialize new Statement from raw line.
+// It will return nil if raw line is empty.
+//
+func ParseStatement(raw []byte) (stmt *Statement, err error) {
+	logp := "ParseStatement"
+
+	raw = bytes.TrimSpace(raw)
+	if len(raw) == 0 {
+		return nil, nil
+	}
+
+	if bytes.HasPrefix(raw, cmdMagicGet) {
+		raw = raw[len(cmdMagicGet):]
+		cmd, args := libexec.ParseCommandArgs(string(raw))
+		if len(cmd) == 0 || len(args) == 0 {
+			return nil, fmt.Errorf("%s: %s missing argument", logp, cmdMagicGet)
+		}
+		stmt = &Statement{
+			kind: statementKindGet,
+			cmd:  cmd,
+			args: args,
+			raw:  raw,
+		}
+		return stmt, nil
+	}
+	if bytes.HasPrefix(raw, cmdMagicPut) {
+		raw = raw[len(cmdMagicPut):]
+		cmd, args := libexec.ParseCommandArgs(string(raw))
+		if len(cmd) == 0 || len(args) == 0 {
+			return nil, fmt.Errorf("%s: %s missing argument", logp, cmdMagicPut)
+		}
+		stmt = &Statement{
+			kind: statementKindPut,
+			cmd:  cmd,
+			args: args,
+			raw:  raw,
+		}
+		return stmt, nil
+	}
+	if bytes.HasPrefix(raw, cmdMagicSudoGet) {
+		raw = raw[len(cmdMagicSudoGet):]
+		cmd, args := libexec.ParseCommandArgs(string(raw))
+		if len(cmd) == 0 || len(args) == 0 {
+			return nil, fmt.Errorf("%s: %s missing argument", logp, cmdMagicSudoGet)
+		}
+		stmt = &Statement{
+			kind: statementKindSudoGet,
+			cmd:  cmd,
+			args: args,
+			raw:  raw,
+		}
+		return stmt, nil
+	}
+	if bytes.HasPrefix(raw, cmdMagicSudoPut) {
+		raw = raw[len(cmdMagicSudoPut):]
+		cmd, args := libexec.ParseCommandArgs(string(raw))
+		if len(cmd) == 0 || len(args) == 0 {
+			return nil, fmt.Errorf("%s: %s missing argument", logp, cmdMagicSudoPut)
+		}
+		stmt = &Statement{
+			kind: statementKindSudoPut,
+			cmd:  cmd,
+			args: args,
+			raw:  raw,
+		}
+		return stmt, nil
+	}
+	if bytes.HasPrefix(raw, cmdMagicRequire) {
+		raw = raw[len(cmdMagicRequire):]
+		cmd, args := libexec.ParseCommandArgs(string(raw))
+		stmt = &Statement{
+			kind: statementKindRequire,
+			cmd:  cmd,
+			args: args,
+			raw:  raw,
+		}
+		return stmt, nil
+	}
+	if raw[0] == '#' {
+		stmt = &Statement{
+			kind: statementKindComment,
+			raw:  raw,
+		}
+		return stmt, nil
+	}
+
+	cmd, args := libexec.ParseCommandArgs(string(raw))
+	stmt = &Statement{
+		cmd:  cmd,
+		args: args,
+		raw:  raw,
+	}
+	return stmt, nil
+}
+
+//
+// ExecLocal execute the command with its arguments in local environment where
+// the output and error send to os.Stdout and os.Stderr respectively.
+//
+func (stmt *Statement) ExecLocal() (err error) {
+	cmd := exec.Command(stmt.cmd, stmt.args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func (stmt *Statement) String() string {
+	return fmt.Sprintf("%s %s", stmt.cmd, strings.Join(stmt.args, " "))
+}