pretty print

src/lib.rs

@@ -29,4 +29,102 @@ pub fn minimize_json(json: &str) -> String {
 		}
 	}
 	result
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum JsonContext {
+	Object, Array, String,
+}
+
+pub fn pretty_json(json: &str, setting: &PrettySetting) -> String {
+	let compressed = minimize_json(json);
+	let dirty = &compressed;
+
+	let mut curr_indentlv = 0;
+	let mut result = String::new();
+	let mut ctx: Vec<JsonContext> = vec![JsonContext::Object]; // Used as stack
+	let mut skip_char = false;
+	let mut last_comma = false;
+
+	for ch in dirty.chars() {
+		if skip_char {
+			skip_char = false;
+			result.push(ch);
+			last_comma = false;
+			continue;
+		}
+
+		if ctx[0] == JsonContext::String {
+			if ch == '\\' {
+				skip_char = true;
+			} else if ch == '\"' {
+				ctx.pop();
+			}
+			result.push(ch);
+			last_comma = false;
+			continue;
+		}
+
+		if ch == '\"' {
+			result.push(ch);
+			ctx.push(JsonContext::String);
+			last_comma = false;
+			continue;
+		}
+
+		if ch == ',' {
+			result.push(ch);
+			result.push('\n');
+			for _ in 0..(curr_indentlv * setting.indent_width) {
+				result.push(' ');
+			}
+			last_comma = true;
+			continue;
+		}
+
+		if ch == '[' || ch == '{' {
+			result.push(ch);
+			result.push('\n');
+			curr_indentlv += 1;
+			for _ in 0..(curr_indentlv * setting.indent_width) {
+				result.push(' ');
+			}
+			ctx.push(match ch {
+				'[' => JsonContext::Array,
+				'{' => JsonContext::Object,
+				_ => unreachable!(),
+			});
+			last_comma = false;
+			continue;
+		}
+
+		if ch == ']' || ch == '}' {
+			curr_indentlv -= 1;
+			if !last_comma {
+				result.push('\n');
+				for _ in 0..(curr_indentlv * setting.indent_width) {
+					result.push(' ');
+				}
+			}
+			result.push(ch);
+			ctx.pop();
+			continue;
+		}
+
+		if ch == ':' {
+			result.push(ch);
+			result.push(' ');
+			continue;
+		}
+
+		result.push(ch);
+	}
+	result.push('\n');
+
+	result
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct PrettySetting {
+	pub indent_width: u32,
 }

src/main.rs

@@ -1,15 +1,28 @@
 extern crate minjson;
 
-
+use std::env;
 use std::io::Read;
 
 use std::io;
 
 fn main() -> () {
+	let args: Vec<String> = env::args().collect();
+	if args.len() != 2 || (args[1] != "minify" && args[1] != "pretty") {
+		eprintln!("Wrong number of arguments");
+		eprintln!("Usage: minjson <operation>");
+		eprintln!("<operation> := minify | pretty");
+		return;
+	}
+
 	let mut strbuf = String::new();
     io::stdin().read_to_string(&mut strbuf).expect("Unable to read json");
 
-    let res = minjson::minimize_json(&strbuf);
+    let res: String;
+    if args[1] == "minify" {
+    	res = minjson::minimize_json(&strbuf);
+    } else {
+    	res = minjson::pretty_json(&strbuf, &minjson::PrettySetting{indent_width: 2});
+    }
 
     print!("{}", res);
 }