refactor output system (#74)

CHANGELOG.md

@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Wiki entry for Gmail users [#58]
 - Info logs for copy/move/delete cmd + silent mode [#74]
 
+### Changed
+
+- Refactor output system + log levels [#74]
+
 ## [0.2.3] - 2021-04-08
 
 ### Added

Cargo.lock

@@ -30,6 +30,17 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "23b62fc65de8e4e7f52534fb52b0f3ed04746ae267519eef2a83941e8085068b"
 
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "autocfg"
 version = "1.0.1"
@@ -194,6 +205,19 @@ dependencies = [
  "cfg-if 1.0.0",
 ]
 
+[[package]]
+name = "env_logger"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "17392a012ea30ef05a610aa97dfb49496e71c9f676b27879922ea5bdf60d9d3f"
+dependencies = [
+ "atty",
+ "humantime",
+ "log",
+ "regex",
+ "termcolor",
+]
+
 [[package]]
 name = "error-chain"
 version = "0.12.4"
@@ -271,14 +295,25 @@ version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
 
+[[package]]
+name = "hermit-abi"
+version = "0.1.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "322f4de77956e22ed0e5032c359a0f1273f1f7f0d79bfa3b8ffbc730d7fbcc5c"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "himalaya"
 version = "0.2.3"
 dependencies = [
  "clap",
+ "env_logger",
  "error-chain",
  "imap",
  "lettre",
+ "log",
  "mailparse",
  "native-tls",
  "rfc2047-decoder",
@@ -325,6 +360,12 @@ version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "494b4d60369511e7dea41cf646832512a94e542f68bb9c49e54518e0f468eb47"
 
+[[package]]
+name = "humantime"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
+
 [[package]]
 name = "hyperx"
 version = "1.3.0"
@@ -475,11 +516,11 @@ dependencies = [
 
 [[package]]
 name = "log"
-version = "0.4.11"
+version = "0.4.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4fabed175da42fed1fa0746b0ea71f412aa9d35e76e95e59b192c64b9dc2bf8b"
+checksum = "51b9bbe6c47d51fc3e1a9b945965946b4c44142ab8792c50835a980d362c2710"
 dependencies = [
- "cfg-if 0.1.10",
+ "cfg-if 1.0.0",
 ]
 
 [[package]]
@@ -1033,6 +1074,15 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dfed899f0eb03f32ee8c6a0aabdb8a7949659e3466561fc0adf54e26d88c5f4"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.1.15"
@@ -1197,6 +1247,15 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"

Cargo.toml

@@ -7,9 +7,11 @@ edition = "2018"
 
 [dependencies]
 clap = {version = "2.33.3", default-features = false, features = ["suggestions"]}
+env_logger = "0.8.3"
 error-chain = "0.12.4"
 imap = "2.4.0"
 lettre = "0.10.0-beta.3"
+log = "0.4.14"
 mailparse = "0.13.1"
 native-tls = "0.2"
 rfc2047-decoder = "0.1.2"

README.md

@@ -87,17 +87,18 @@ soywod <clement.douin@posteo.net>
 📫 Minimalist CLI email client
 
 USAGE:
-    himalaya [FLAGS] [OPTIONS] [SUBCOMMAND]
+    himalaya [OPTIONS] [SUBCOMMAND]
 
 FLAGS:
     -h, --help       Prints help information
-    -s, --silent     Disables any output
     -V, --version    Prints version information
 
 OPTIONS:
     -a, --account <STRING>     Selects a specific account
+    -l, --log <LEVEL>          Defines the logs level [default: info]  [possible values: error, warn, info, debug,
+                               trace]
     -m, --mailbox <MAILBOX>    Selects a specific mailbox [default: INBOX]
-    -o, --output <STRING>      Defines the output format [default: plain]  [possible values: plain, json]
+    -o, --output <FMT>         Defines the output format [default: plain]  [possible values: plain, json]
 
 SUBCOMMANDS:
     attachments    Downloads all message attachments

src/main.rs

@@ -7,6 +7,8 @@ mod config {
 }
 mod output {
     pub(crate) mod cli;
+    pub(crate) mod fmt;
+    pub(crate) mod log;
     pub(crate) mod utils;
 }
 mod imap {
@@ -28,6 +30,7 @@ mod mbox {
 
 use clap;
 use error_chain::error_chain;
+use log::{debug, error};
 use std::env;
 
 use crate::{
@@ -36,7 +39,11 @@ use crate::{
     imap::cli::{imap_matches, imap_subcmds},
     mbox::cli::{mbox_matches, mbox_source_arg, mbox_subcmds},
     msg::cli::{msg_matches, msg_subcmds},
-    output::cli::output_args,
+    output::{
+        cli::output_args,
+        fmt::OutputFmt,
+        log::{init as init_logger, LogLevel},
+    },
 };
 
 error_chain! {
@@ -45,6 +52,7 @@ error_chain! {
         ImapCli(crate::imap::cli::Error, crate::imap::cli::ErrorKind);
         MboxCli(crate::mbox::cli::Error, crate::mbox::cli::ErrorKind);
         MsgCli(crate::msg::cli::Error, crate::msg::cli::ErrorKind);
+        OutputLog(crate::output::log::Error, crate::output::log::ErrorKind);
     }
 }
 
@@ -62,6 +70,14 @@ fn run() -> Result<()> {
         .subcommands(msg_subcmds())
         .get_matches();
 
+    let output_fmt: OutputFmt = matches.value_of("output").unwrap().into();
+    let log_level: LogLevel = matches.value_of("log").unwrap().into();
+
+    init_logger(&output_fmt, &log_level)?;
+    debug!("Logger initialized");
+    debug!("Output format: {}", &output_fmt);
+    debug!("Log level: {}", &log_level);
+
     loop {
         if mbox_matches(&matches)? {
             break;
@@ -88,8 +104,8 @@ fn main() {
         match errs.next() {
             None => (),
             Some(err) => {
-                eprintln!("{}", err);
+                error!("{}", err);
-                errs.for_each(|err| eprintln!(" ↳ {}", err));
+                errs.for_each(|err| error!(" ↳ {}", err));
             }
         }
     }

src/msg/cli.rs

@@ -1,5 +1,6 @@
 use clap::{self, App, Arg, ArgMatches, SubCommand};
 use error_chain::error_chain;
+use log::{debug, error, info};
 use std::{fs, ops::Deref};
 
 use crate::{
@@ -9,7 +10,6 @@ use crate::{
     input,
     mbox::cli::mbox_target_arg,
     msg::model::{Attachments, Msg, Msgs, ReadableMsg},
-    output::utils::{print, Info},
     smtp,
 };
 
@@ -19,7 +19,6 @@ error_chain! {
         Imap(crate::imap::model::Error, crate::imap::model::ErrorKind);
         Input(crate::input::Error, crate::input::ErrorKind);
         MsgModel(crate::msg::model::Error, crate::msg::model::ErrorKind);
-        OutputUtils(crate::output::utils::Error, crate::output::utils::ErrorKind);
         Smtp(crate::smtp::Error, crate::smtp::ErrorKind);
     }
 }
@@ -162,25 +161,33 @@ pub fn msg_subcmds<'a>() -> Vec<App<'a, 'a>> {
 pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
     let config = Config::new_from_file()?;
     let account = config.find_account_by_name(matches.value_of("account"))?;
-    let output_fmt = matches.value_of("output").unwrap();
-    let silent = matches.is_present("silent");
     let mbox = matches.value_of("mailbox").unwrap();
 
     if let Some(matches) = matches.subcommand_matches("list") {
+        debug!("Subcommand matched: list");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let page_size: usize = matches.value_of("page-size").unwrap().parse().unwrap();
+        debug!("Page size: {}", &page_size);
         let page: usize = matches.value_of("page").unwrap().parse().unwrap();
+        debug!("Page: {}", &page);
+
         let msgs = imap_conn.list_msgs(&mbox, &page_size, &page)?;
         let msgs = Msgs::from(&msgs);
-        print(&output_fmt, &silent, msgs)?;
+        info!("{}", msgs);
+
         imap_conn.logout();
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("search") {
+        debug!("Subcommand matched: search");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let page_size: usize = matches.value_of("page-size").unwrap().parse().unwrap();
+        debug!("Page size: {}", &page_size);
         let page: usize = matches.value_of("page").unwrap().parse().unwrap();
+        debug!("Page: {}", &page);
         let query = matches
             .values_of("query")
             .unwrap_or_default()
@@ -205,62 +212,61 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
             })
             .1
             .join(" ");
+        debug!("Query: {}", &query);
+
         let msgs = imap_conn.search_msgs(&mbox, &query, &page_size, &page)?;
         let msgs = Msgs::from(&msgs);
-        print(&output_fmt, &silent, msgs)?;
+        info!("{}", msgs);
+
         imap_conn.logout();
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("read") {
+        debug!("Subcommand matched: read");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let uid = matches.value_of("uid").unwrap();
+        debug!("UID: {}", &uid);
         let mime = format!("text/{}", matches.value_of("mime-type").unwrap());
+        debug!("MIME: {}", &mime);
+
         let msg = imap_conn.read_msg(&mbox, &uid)?;
         let msg = ReadableMsg::from_bytes(&mime, &msg)?;
-        print(&output_fmt, &silent, msg)?;
+        info!("{}", msg);
+
         imap_conn.logout();
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("attachments") {
+        debug!("Subcommand matched: attachments");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let uid = matches.value_of("uid").unwrap();
+        debug!("UID: {}", &uid);
 
         let msg = imap_conn.read_msg(&mbox, &uid)?;
         let attachments = Attachments::from_bytes(&msg)?;
-
+        debug!(
-        match output_fmt {
-            "plain" => {
-                println!(
             "{} attachment(s) found for message {}",
             attachments.0.len(),
             uid
         );
-
         attachments.0.iter().for_each(|attachment| {
             let filepath = config.downloads_filepath(&account, &attachment.filename);
-                    println!("Downloading {}…", &attachment.filename);
+            debug!("Downloading {}…", &attachment.filename);
             fs::write(filepath, &attachment.raw).unwrap()
         });
+        info!("{} attachment(s) successfully downloaded", &uid);
 
-                println!("Done!");
-            }
-            "json" => {
-                attachments.0.iter().for_each(|attachment| {
-                    let filepath = config.downloads_filepath(&account, &attachment.filename);
-                    fs::write(filepath, &attachment.raw).unwrap()
-                });
-
-                print!("{{}}");
-            }
-            _ => (),
-        }
         imap_conn.logout();
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("write") {
+        debug!("Subcommand matched: write");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let attachments = matches
             .values_of("attachments")
@@ -276,17 +282,17 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
             match input::post_edit_choice() {
                 Ok(choice) => match choice {
                     input::Choice::Send => {
-                        println!("Sending…");
+                        debug!("Sending message…");
                         let msg = msg.to_sendable_msg()?;
                         smtp::send(&account, &msg)?;
                         imap_conn.append_msg("Sent", &msg.formatted(), &[Flag::Seen])?;
-                        println!("Done!");
+                        info!("Message successfully sent");
                         break;
                     }
                     input::Choice::Draft => {
-                        println!("Saving to draft…");
+                        debug!("Saving to draft…");
                         imap_conn.append_msg("Drafts", &msg.to_vec()?, &[Flag::Seen])?;
-                        println!("Done!");
+                        info!("Message successfully saved to Drafts");
                         break;
                     }
                     input::Choice::Edit => {
@@ -295,7 +301,7 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
                     }
                     input::Choice::Quit => break,
                 },
-                Err(err) => eprintln!("{}", err),
+                Err(err) => error!("{}", err),
             }
         }
         imap_conn.logout();
@@ -303,30 +309,44 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
     }
 
     if let Some(matches) = matches.subcommand_matches("template") {
+        debug!("Subcommand matched: template");
+
         if let Some(_) = matches.subcommand_matches("new") {
+            debug!("Subcommand matched: new");
+
             let tpl = Msg::build_new_tpl(&config, &account)?;
-            print(&output_fmt, &silent, &tpl)?;
+            info!("{}", tpl);
         }
 
         if let Some(matches) = matches.subcommand_matches("reply") {
+            debug!("Subcommand matched: reply");
+
             let mut imap_conn = ImapConnector::new(&account)?;
             let uid = matches.value_of("uid").unwrap();
+            debug!("UID: {}", &uid);
+
             let msg = Msg::from(imap_conn.read_msg(&mbox, &uid)?);
             let tpl = if matches.is_present("reply-all") {
                 msg.build_reply_all_tpl(&config, &account)?
             } else {
                 msg.build_reply_tpl(&config, &account)?
             };
-            print(&output_fmt, &silent, &tpl)?;
+            info!("{}", tpl);
+
             imap_conn.logout();
         }
 
         if let Some(matches) = matches.subcommand_matches("forward") {
+            debug!("Subcommand matched: forward");
+
             let mut imap_conn = ImapConnector::new(&account)?;
             let uid = matches.value_of("uid").unwrap();
+            debug!("UID: {}", &uid);
+
             let msg = Msg::from(imap_conn.read_msg(&mbox, &uid)?);
             let tpl = msg.build_forward_tpl(&config, &account)?;
-            print(&output_fmt, &silent, &tpl)?;
+            info!("{}", tpl);
+
             imap_conn.logout();
         }
 
@@ -334,6 +354,8 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
     }
 
     if let Some(matches) = matches.subcommand_matches("reply") {
+        debug!("Subcommand matched: reply");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let attachments = matches
             .values_of("attachments")
@@ -341,6 +363,7 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
             .map(String::from)
             .collect::<Vec<_>>();
         let uid = matches.value_of("uid").unwrap();
+        debug!("UID: {}", &uid);
 
         let msg = Msg::from(imap_conn.read_msg(&mbox, &uid)?);
         let tpl = if matches.is_present("reply-all") {
@@ -357,17 +380,17 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
             match input::post_edit_choice() {
                 Ok(choice) => match choice {
                     input::Choice::Send => {
-                        println!("Sending…");
+                        debug!("Sending message…");
                         smtp::send(&account, &msg.to_sendable_msg()?)?;
                         imap_conn.append_msg("Sent", &msg.to_vec()?, &[Flag::Seen])?;
                         imap_conn.add_flags(mbox, uid, "\\Answered")?;
-                        println!("Done!");
+                        info!("Message successfully sent");
                         break;
                     }
                     input::Choice::Draft => {
-                        println!("Saving to draft…");
+                        debug!("Saving draft message…");
                         imap_conn.append_msg("Drafts", &msg.to_vec()?, &[Flag::Seen])?;
-                        println!("Done!");
+                        info!("Message successfully saved to Drafts");
                         break;
                     }
                     input::Choice::Edit => {
@@ -376,7 +399,7 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
                     }
                     input::Choice::Quit => break,
                 },
-                Err(err) => eprintln!("{}", err),
+                Err(err) => error!("{}", err),
             }
         }
 
@@ -385,6 +408,8 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
     }
 
     if let Some(matches) = matches.subcommand_matches("forward") {
+        debug!("Subcommand matched: forward");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let attachments = matches
             .values_of("attachments")
@@ -392,6 +417,7 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
             .map(String::from)
             .collect::<Vec<_>>();
         let uid = matches.value_of("uid").unwrap();
+        debug!("UID: {}", &uid);
 
         let msg = Msg::from(imap_conn.read_msg(&mbox, &uid)?);
         let tpl = msg.build_forward_tpl(&config, &account)?;
@@ -403,16 +429,16 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
             match input::post_edit_choice() {
                 Ok(choice) => match choice {
                     input::Choice::Send => {
-                        println!("Sending…");
+                        debug!("Sending message…");
                         smtp::send(&account, &msg.to_sendable_msg()?)?;
                         imap_conn.append_msg("Sent", &msg.to_vec()?, &[Flag::Seen])?;
-                        println!("Done!");
+                        info!("Message successfully sent");
                         break;
                     }
                     input::Choice::Draft => {
-                        println!("Saving to draft…");
+                        debug!("Saving draft message…");
                         imap_conn.append_msg("Drafts", &msg.to_vec()?, &[Flag::Seen])?;
-                        println!("Done!");
+                        info!("Message successfully saved to Drafts");
                         break;
                     }
                     input::Choice::Edit => {
@@ -421,7 +447,7 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
                     }
                     input::Choice::Quit => break,
                 },
-                Err(err) => eprintln!("{}", err),
+                Err(err) => error!("{}", err),
             }
         }
 
@@ -430,63 +456,67 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
     }
 
     if let Some(matches) = matches.subcommand_matches("copy") {
+        debug!("Subcommand matched: copy");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let uid = matches.value_of("uid").unwrap();
+        debug!("UID: {}", &uid);
         let target = matches.value_of("target").unwrap();
+        debug!("Target: {}", &target);
+
         let msg = Msg::from(imap_conn.read_msg(&mbox, &uid)?);
         let mut flags = msg.flags.deref().to_vec();
         flags.push(Flag::Seen);
         imap_conn.append_msg(target, &msg.raw, &flags)?;
-        imap_conn.logout();
+        info!(
-
-        print(
-            &output_fmt,
-            &silent,
-            Info(format!(
             "Message {} successfully copied to folder `{}`",
             &uid, &target
-            )),
+        );
-        )?;
+
+        imap_conn.logout();
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("move") {
+        debug!("Subcommand matched: move");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let uid = matches.value_of("uid").unwrap();
+        debug!("UID: {}", &uid);
         let target = matches.value_of("target").unwrap();
+        debug!("Target: {}", &target);
+
         let msg = Msg::from(imap_conn.read_msg(&mbox, &uid)?);
         let mut flags = msg.flags.deref().to_vec();
         flags.push(Flag::Seen);
         imap_conn.append_msg(target, &msg.raw, msg.flags.deref())?;
         imap_conn.add_flags(mbox, uid, "\\Seen \\Deleted")?;
-        imap_conn.logout();
+        info!(
-
-        print(
-            &output_fmt,
-            &silent,
-            Info(format!(
             "Message {} successfully moved to folder `{}`",
             &uid, &target
-            )),
+        );
-        )?;
+
+        imap_conn.logout();
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("delete") {
+        debug!("Subcommand matched: delete");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let uid = matches.value_of("uid").unwrap();
-        imap_conn.add_flags(mbox, uid, "\\Seen \\Deleted")?;
+        debug!("UID: {}", &uid);
-        imap_conn.logout();
 
-        print(
+        imap_conn.add_flags(mbox, uid, "\\Seen \\Deleted")?;
-            &output_fmt,
+        info!("Message {} successfully deleted", &uid);
-            &silent,
+
-            Info(format!("Message {} successfully deleted", &uid)),
+        imap_conn.logout();
-        )?;
         return Ok(());
     }
 
     if let Some(matches) = matches.subcommand_matches("send") {
+        debug!("Subcommand matched: send");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let msg = matches.value_of("message").unwrap();
         let msg = Msg::from(msg.to_string());
@@ -498,6 +528,8 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
     }
 
     if let Some(matches) = matches.subcommand_matches("save") {
+        debug!("Subcommand matched: save");
+
         let mut imap_conn = ImapConnector::new(&account)?;
         let msg = matches.value_of("message").unwrap();
         let msg = Msg::from(msg.to_string());
@@ -506,11 +538,13 @@ pub fn msg_matches(matches: &ArgMatches) -> Result<()> {
         return Ok(());
     }
 
-    // Default case: list first page messages
+    debug!("Default subcommand matched: list");
+
     let mut imap_conn = ImapConnector::new(&account)?;
     let msgs = imap_conn.list_msgs(&mbox, &10, &0)?;
     let msgs = Msgs::from(&msgs);
-    print(&output_fmt, &silent, msgs)?;
+    info!("{}", &msgs);
+
     imap_conn.logout();
     Ok(())
 }

src/output/cli.rs

@@ -6,12 +6,15 @@ pub fn output_args<'a>() -> Vec<Arg<'a, 'a>> {
             .long("output")
             .short("o")
             .help("Defines the output format")
-            .value_name("STRING")
+            .value_name("FMT")
             .possible_values(&["plain", "json"])
             .default_value("plain"),
-        Arg::with_name("silent")
+        Arg::with_name("log")
-            .long("silent")
+            .long("log")
-            .short("s")
+            .short("l")
-            .help("Disables any output"),
+            .help("Defines the logs level")
+            .value_name("LEVEL")
+            .possible_values(&["error", "warn", "info", "debug", "trace"])
+            .default_value("info"),
     ]
 }

src/output/fmt.rs

@@ -0,0 +1,28 @@
+use std::fmt;
+
+pub enum OutputFmt {
+    Json,
+    Plain,
+}
+
+impl From<&str> for OutputFmt {
+    fn from(s: &str) -> Self {
+        match s {
+            "json" => Self::Json,
+            "plain" | _ => Self::Plain,
+        }
+    }
+}
+
+impl fmt::Display for OutputFmt {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}",
+            match *self {
+                OutputFmt::Json => "JSON",
+                OutputFmt::Plain => "PLAIN",
+            },
+        )
+    }
+}

src/output/log.rs

@@ -0,0 +1,86 @@
+use error_chain::error_chain;
+use log::{Level, LevelFilter, Metadata, Record};
+use std::fmt;
+
+use super::fmt::OutputFmt;
+
+error_chain! {}
+
+// Log level struct
+
+pub struct LogLevel(pub LevelFilter);
+
+impl From<&str> for LogLevel {
+    fn from(s: &str) -> Self {
+        match s {
+            "error" => Self(LevelFilter::Error),
+            "warn" => Self(LevelFilter::Warn),
+            "debug" => Self(LevelFilter::Debug),
+            "trace" => Self(LevelFilter::Trace),
+            "info" | _ => Self(LevelFilter::Info),
+        }
+    }
+}
+
+impl fmt::Display for LogLevel {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.0.to_string())
+    }
+}
+
+// Plain logger
+
+struct PlainLogger;
+
+impl log::Log for PlainLogger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        metadata.level() <= Level::Trace
+    }
+
+    fn log(&self, record: &Record) {
+        if self.enabled(record.metadata()) {
+            if let Level::Error = record.level() {
+                eprintln!("{}", record.args());
+            } else {
+                println!("{}", record.args());
+            }
+        }
+    }
+
+    fn flush(&self) {}
+}
+
+// JSON logger
+
+struct JsonLogger;
+
+impl log::Log for JsonLogger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        [Level::Error, Level::Info].contains(&metadata.level())
+    }
+
+    fn log(&self, record: &Record) {
+        if self.enabled(record.metadata()) {
+            if let Level::Error = record.level() {
+                eprintln!("{}", record.args());
+            } else {
+                // Should be safe enough to `.unwrap()` since it's
+                // formatted by Himalaya itself
+                print!("{}", serde_json::to_string(record.args()).unwrap());
+            }
+        }
+    }
+
+    fn flush(&self) {}
+}
+
+// Init
+
+pub fn init(fmt: &OutputFmt, level: &LogLevel) -> Result<()> {
+    log::set_boxed_logger(match fmt {
+        &OutputFmt::Json => Box::new(JsonLogger),
+        &OutputFmt::Plain => Box::new(PlainLogger),
+    })
+    .map(|()| log::set_max_level(level.0))
+    .chain_err(|| "Could not init logger")
+}