Adding flag and logic for different output format (#185)

src/printer.rs

@@ -0,0 +1,82 @@
+use colored::Colorize;
+use std::io::Write;
+
+use anyhow::Result;
+use clap::ValueEnum;
+
+use crate::message::Message;
+use crate::tell_user;
+
+#[derive(Clone, ValueEnum, PartialEq, Eq, Debug)]
+pub enum SerializationFormat {
+    Text,
+    Json,
+}
+
+pub struct Printer<W> {
+    pub writer: W,
+    format: SerializationFormat,
+}
+
+impl<W: Write> Printer<W> {
+    pub fn new(writer: W, format: SerializationFormat) -> Self {
+        Self { writer, format }
+    }
+
+    pub fn write_once(&mut self, messages: &[Message]) -> Result<()> {
+        let (fixed, outstanding): (Vec<&Message>, Vec<&Message>) =
+            messages.iter().partition(|message| message.fixed);
+        let num_fixable = outstanding
+            .iter()
+            .filter(|message| message.kind.fixable())
+            .count();
+
+        match self.format {
+            SerializationFormat::Json => {
+                writeln!(self.writer, "{}", serde_json::to_string_pretty(&messages)?)?
+            }
+            SerializationFormat::Text => {
+                if !fixed.is_empty() {
+                    writeln!(
+                        self.writer,
+                        "Found {} error(s) ({} fixed).",
+                        outstanding.len(),
+                        fixed.len()
+                    )?
+                } else {
+                    writeln!(self.writer, "Found {} error(s).", outstanding.len())?
+                }
+
+                for message in outstanding {
+                    writeln!(self.writer, "{}", message)?
+                }
+
+                if num_fixable > 0 {
+                    writeln!(
+                        self.writer,
+                        "{num_fixable} potentially fixable with the --fix option."
+                    )?
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    pub fn write_continuously(&mut self, messages: &[Message]) -> Result<()> {
+        tell_user!(
+            self.writer,
+            "Found {} error(s). Watching for file changes.",
+            messages.len(),
+        );
+
+        if !messages.is_empty() {
+            writeln!(self.writer, "\n")?;
+            for message in messages {
+                writeln!(self.writer, "{}", message)?
+            }
+        }
+
+        Ok(())
+    }
+}