Suggestion: Try applying a change to the file (WIP)

Not working yet, but the idea is to get the file referenced by the
suggestion and apply the suggested change directly to it.

Here, we read the original file, and write its contents to the new file,
replacing the lines modified by the suggestion with the suggested
change.

Currently doesn't work because you can't pass file instances to
`fs::rename`, only paths.

I'd like to try a slightly different system so I can keep the original
file's creation date. With the current system, it would be overwritten
by the new temporary file created to store the change.

3 files changed, 130 insertions, 0 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 3cad2f3..e8b4f7f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -221,6 +221,17 @@ dependencies = [
 ]
 
 [[package]]
+name = "getrandom"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7abc8dd8451921606d809ba32e95b6111925cd2906060d2dcc29c070220503eb"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
 name = "gimli"
 version = "0.22.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -235,6 +246,7 @@ dependencies = [
  "regex",
  "serde",
  "serde_json",
+ "tempfile",
  "thiserror",
  "unidiff",
 ]
@@ -669,6 +681,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d36492546b6af1463394d46f0c834346f31548646f6ba10849802c9c9a27ac33"
 
 [[package]]
+name = "ppv-lite86"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
+
+[[package]]
 name = "proc-macro2"
 version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -687,6 +705,47 @@ dependencies = [
 ]
 
 [[package]]
+name = "rand"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
+dependencies = [
+ "getrandom",
+ "libc",
+ "rand_chacha",
+ "rand_core",
+ "rand_hc",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f4c8ed856279c9737206bf725bf36935d8666ead7aa69b52be55af369d193402"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_hc"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca3129af7b92a17112d59ad498c6f81eaf463253766b90396d39ea7a39d6613c"
+dependencies = [
+ "rand_core",
+]
+
+[[package]]
 name = "redox_syscall"
 version = "0.1.57"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -711,6 +770,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "26412eb97c6b088a6997e05f69403a802a92d520de2f8e63c2b65f9e0f47c4e8"
 
 [[package]]
+name = "remove_dir_all"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3acd125665422973a33ac9d3dd2df85edad0f4ae9b00dafb1a05e43a9f5ef8e7"
+dependencies = [
+ "winapi 0.3.9",
+]
+
+[[package]]
 name = "ring"
 version = "0.14.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -869,6 +937,20 @@ dependencies = [
 ]
 
 [[package]]
+name = "tempfile"
+version = "3.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "rand",
+ "redox_syscall",
+ "remove_dir_all",
+ "winapi 0.3.9",
+]
+
+[[package]]
 name = "thiserror"
 version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1219,6 +1301,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "wasi"
+version = "0.9.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
+
+[[package]]
 name = "webpki"
 version = "0.19.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index 8fb2e65..7f5a472 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,5 +9,6 @@ github-rs = "0.7.0"
 regex = "1.3.9"
 serde = { version = "1.0.114", features = ["derive"] }
 serde_json = "1.0.56"
+tempfile = "3.1.0"
 thiserror = "1.0.20"
 unidiff = "0.3.3"
diff --git a/src/lib.rs b/src/lib.rs
index e4c45c2..b368747 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,11 +1,17 @@
 #![warn(rust_2018_idioms)]
 
 
+use std::fs;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Write};
+
+use git2::Repository;
 use github_rs::client::{Executor, Github};
 use regex::Regex;
 use serde::Deserialize;
 use serde_json::Value;
 use thiserror::Error;
+use tempfile::tempfile;
 
 
 #[derive(Debug, Error)]
@@ -61,6 +67,11 @@ pub struct Suggestion {
 
     #[serde(rename = "body")]
     suggestion: String,
+
+    path: String,
+
+    original_start_line: usize,
+    original_end_line: usize,
 }
 
 impl Suggestion {
@@ -90,6 +101,36 @@ impl Suggestion {
         let s = re.replace(&self.suggestion, "+");
         s.replace("```", "")
     }
+
+    fn apply(&self) -> Result<(), Error> {
+        let repo = Repository::open(".").unwrap();
+        let repo_root = repo.workdir().unwrap();
+
+        let original = File::open(repo_root.join(&self.path)).unwrap();
+        let metadata = original.metadata().unwrap();
+        let created_at = metadata.created().unwrap();
+        let mut reader = BufReader::new(original);
+
+        let mut new = tempfile().unwrap();
+
+        for (i, line) in reader.lines().enumerate() {
+            match line {
+                Ok(l) => {
+                    if i < self.original_start_line
+                            || i > self.original_end_line {
+                        writeln!(new, "{}", l).unwrap();
+                    } else if i == self.original_end_line {
+                        write!(new, "{}", self.suggestion()).unwrap();
+                    }
+                },
+                Err(e) => panic!(e),
+            }
+        }
+
+        fs::rename(new, original).unwrap();
+
+        Ok(())
+    }
 }
 
 #[cfg(test)]