From: Harishankar <v.harishankar@gmail.com>
Date: Sun, 31 May 2020 10:46:26 +0000 (+0530)
Subject: Added command history saving with rustyline
X-Git-Tag: 0.1-a^0
X-Git-Url: https://harishankar.org/repos/?p=evpf.git;a=commitdiff_plain;h=a86a7c0712840275401e5ccd79322f3575b918fb

Added command history saving with rustyline
Added functionality to save the command history in evpf with
rustyline load_history and save_history
---

diff --git a/src/main.rs b/src/main.rs
index f46dfab..8e54265 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,6 +2,7 @@ use regex::Regex;
 use colored::*;
 use std::env;
 use rustyline::Editor;
+use std::path::PathBuf;
 
 const ILLEGAL_EXP : &'static str = "Illegal Expression";
 const ERR_PARSING_NOT_MATCH : &'static str = "Error parsing expression! \
@@ -13,6 +14,13 @@ const HELP_TEXT : [&str ; 4] =
 				 "Supported operators: +, -, *, /",
 				 "Type q, Q to quit"
 				 ];
+				 
+const HOMEDIR_NOT_FOUND : &'static str = "User home directory not found \
+				(missing environment?).";
+				
+const HISTORY_FILE_NOT_FOUND : &'static str = "History file not found.";
+
+const SAVE_HISTORY_ERROR : &'static str = "Unable to save command history!";
 
 const ERROR : &'static str = "Error";
 const ERROR_HELP : &'static str = "Type ? or h or H for help";
@@ -156,6 +164,30 @@ fn run_command_line (args : &Vec<String>, match_num : &regex::Regex) {
 	}
 }
 
+// get the history file name as string - home dir + .evpfhistory
+fn get_history_file () -> Result<String,String> {
+	// get the environment variable HOME
+	let home_path = env::var ("HOME");
+	// if not found, return an error
+	if home_path.is_err () {
+		return Err (HOMEDIR_NOT_FOUND.to_string());
+	}
+	// build the path for the history file i.e. homedir + .evpfhistory in
+	// platform independent way
+	let mut hist_file = PathBuf::new ();
+	hist_file.push (home_path.unwrap());
+	hist_file.push (".evpfhistory");	
+	
+	// if cannot convert to string return error 
+	if hist_file.to_str ().is_none () {
+		return Err (HOMEDIR_NOT_FOUND.to_string());
+	}
+	
+	// return the history file path as a string
+	let hist_file_path = String::from (hist_file.to_str().unwrap());
+	return Ok (hist_file_path);
+}
+
 // Interactive mode - display the prompt and evaluate expressions entered into
 // the prompt - until user quits
 fn run_interactive_mode (match_num : &regex::Regex) {
@@ -163,6 +195,14 @@ fn run_interactive_mode (match_num : &regex::Regex) {
 	let mut expr = String::new ();
 
 	let mut rl = Editor::<()>::new ();
+	let hist_file = get_history_file ();
+	if hist_file.is_err () {
+		eprintln! ("{}", &hist_file.unwrap_err());
+	} else {
+		if rl.load_history (&hist_file.unwrap ()).is_err () {
+			eprintln! ("{}", HISTORY_FILE_NOT_FOUND.purple());
+		}
+	}
 	// loop until a blank line is received	
 	loop {
 		expr.clear ();
@@ -205,6 +245,13 @@ fn run_interactive_mode (match_num : &regex::Regex) {
 			eprintln! ("{}", ERROR_HELP.purple());
 		}
 	}
+	// save the history 
+	let hist_file = get_history_file ();
+	if ! hist_file.is_err () {
+		if rl.save_history (&hist_file.unwrap()).is_err () {
+			eprintln! ("{}", SAVE_HISTORY_ERROR);
+		}
+	} 
 }
 
 fn main() {