From 3781894ffc29456c5039daddab9482a02a70dd82 Mon Sep 17 00:00:00 2001
From: Dima Kudosh <LagMegantic@yandex.ru>
Date: Sun, 28 Feb 2016 19:14:11 +0300
Subject: [PATCH] Add context diff and tests for it

---
 src/lib.rs    | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 src/utils.rs  | 15 +++++++++++-
 tests/test.rs |  8 +++++++
 3 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 38082df..52c2150 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,8 +3,9 @@ pub mod differ;
 mod utils;
 
 
+use std::collections::HashMap;
 use sequencematcher::{SequenceMatcher, Sequence};
-use utils::{format_range_unified};
+use utils::{format_range_unified, format_range_context};
 
 
 pub fn get_close_matches<'a>(word: &str, possibilities: Vec<&'a str>, n: usize, cutoff: f32) -> Vec<&'a str> {
@@ -63,3 +64,64 @@ pub fn unified_diff<T: Sequence>(first_sequence: &T, second_sequence: &T, from_f
 	}
 	res
 }
+
+
+pub fn context_diff<T: Sequence>(first_sequence: &T, second_sequence: &T, from_file: &str, to_file: &str, 
+	from_file_date: &str, to_file_date: &str, n: usize, lineterm: &str) -> Vec<String> {
+	let mut res = Vec::new();
+	let mut prefix: HashMap<String, String> = HashMap::new();
+	prefix.insert(String::from("insert"), String::from("+ "));
+	prefix.insert(String::from("delete"), String::from("- "));
+	prefix.insert(String::from("replace"), String::from("! "));
+	prefix.insert(String::from("equal"), String::from("  "));
+	let mut started = false;
+	let mut matcher = SequenceMatcher::new(first_sequence, second_sequence);
+	for group in &matcher.get_grouped_opcodes(n) {
+		if !started {
+			started = true;
+			let from_date = format!("\t{}", from_file_date);
+			let to_date = format!("\t{}", to_file_date);
+			res.push( format!("*** {}{}{}", from_file, from_date, lineterm) );
+			res.push( format!("--- {}{}{}", to_file, to_date, lineterm) );
+		}
+		let (first, last) = (group.first().unwrap(), group.last().unwrap());
+		res.push(format!("***************{}", lineterm));
+		let file1_range = format_range_context(first.first_start, last.first_end); 
+		res.push(format!("*** {} ****{}", file1_range, lineterm));
+		let mut any = false;
+		for opcode in group {
+			if opcode.tag == "replace" || opcode.tag == "delete" {
+				any = true;
+				break;
+			}
+		}
+		if any {
+			for opcode in group {
+				if opcode.tag != "insert" {
+					for i in opcode.first_start..opcode.first_end {
+						res.push( format!("{}{}", prefix.get(&opcode.tag).unwrap(), first_sequence.at_index(i).unwrap()) );
+					}
+				}
+			}
+		}
+		let file2_range = format_range_context(first.second_start, last.second_end);
+		res.push(format!("--- {} ----{}", file1_range, lineterm));
+		any = false;
+		for opcode in group {
+			if opcode.tag == "replace" || opcode.tag == "insert" {
+				any = true;
+				break;
+			}
+		}
+		if any {
+			for opcode in group {
+				if opcode.tag != "delete" {
+					for i in opcode.second_start..opcode.second_end {
+						res.push( format!("{}{}", prefix.get(&opcode.tag).unwrap(), second_sequence.at_index(i).unwrap()) );
+					}
+				}
+			}
+		}
+	}
+	res
+}
\ No newline at end of file
diff --git a/src/utils.rs b/src/utils.rs
index a855a9e..da3f1e3 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -30,10 +30,23 @@ pub fn format_range_unified(start:usize, end: usize) -> String {
     println!("{:?} {}", start, end);
     let length = end - start;
     if length == 1 {
-        return format!("{}", beginning)
+        return beginning.to_string()
     }
     if length == 0 {
         beginning -= 1;
     }
     format!("{},{}", beginning, length)
+}
+
+
+pub fn format_range_context(start: usize, end: usize) -> String {
+    let mut beginning = start + 1;
+    let length = end - start;
+    if length == 0 {
+        beginning -= 1
+    }
+    if length <= 1 {
+        return beginning.to_string()
+    }
+    format!("{},{}", beginning, beginning + length - 1)
 }
\ No newline at end of file
diff --git a/tests/test.rs b/tests/test.rs
index 58ef026..b0f5051 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -109,5 +109,13 @@ fn test_unified_diff() {
     let result = difflib::unified_diff(&first_text, &second_text, "Original", "Current",
              "2005-01-26 23:30:50", "2010-04-02 10:20:52", 3, "").join("");
     assert_eq!(result, "--- Original\t2005-01-26 23:30:50+++ Current\t2010-04-02 10:20:52@@ -1,4 +1,4 @@+zero one-two-three+tree four");
+}
 
+#[test]
+fn test_context_diff() {
+    let first_text = "one two three four".split(" ").collect::<Vec<&str>>();
+    let second_text = "zero one tree four".split(" ").collect::<Vec<&str>>();
+    let result = difflib::context_diff(&first_text, &second_text, "Original", "Current",
+             "2005-01-26 23:30:50", "2010-04-02 10:20:52", 3, "").join("");
+    assert_eq!(result, "*** Original\t2005-01-26 23:30:50--- Current\t2010-04-02 10:20:52****************** 1,4 ****  one! two! three  four--- 1,4 ----+ zero  one! tree  four");
 }
\ No newline at end of file