Extract review logic into bot_actions module

Move `exec_review`, `download_git_diff`, and review formatting
to a new `bot_actions::review` module. Update the review flow to
post inline review comments via the Gitea API and simplify the
comment markdown to a summary. Add diff formatting that
preprocesses added lines with line numbers for the LLM prompt.

src/bot_actions/mod.rs

@@ -0,0 +1 @@
+pub mod review;

src/bot_actions/review.rs

@@ -0,0 +1,201 @@
+use futures_util::stream::TryStreamExt;
+use tokio::io::AsyncReadExt;
+use tokio_util::io::StreamReader;
+
+use crate::{
+    bot::ReviewResult,
+    consts::{BOT_PROCESS_MSG, MAX_DIFF_SIZE, REVIEW_PROMPT},
+    errors::AppError,
+    gitea::{GiteaAPI, ReviewPayload},
+    open_router::OpenRouterClient,
+};
+
+pub async fn exec_review(
+    gitea_api: &GiteaAPI,
+    open_router_client: &OpenRouterClient,
+    http_client: &reqwest::Client,
+    model: &str,
+    review_payload: ReviewPayload,
+) -> Result<(), AppError> {
+    let new_comment = gitea_api
+        .comment(
+            &BOT_PROCESS_MSG.replace("{model}", model),
+            &review_payload.repository.full_name,
+            review_payload.pull_request.number,
+        )
+        .await?;
+
+    let bot_result: Result<ReviewResult, anyhow::Error> = async {
+        let git_diff =
+            download_git_diff(&http_client, &review_payload.pull_request.diff_url).await?;
+
+        let diff_for_llm = format_diff_for_review(&git_diff);
+
+        let bot_request = REVIEW_PROMPT
+            .replace("{subject}", &review_payload.pull_request.title)
+            .replace("{comment}", &review_payload.comment.body)
+            .replace("{diff}", &diff_for_llm);
+
+        let chat_result = open_router_client.chat(&bot_request).await?;
+        let mut review_result = serde_json::from_str::<ReviewResult>(&chat_result.message)?;
+
+        review_result.cost = chat_result.cost;
+
+        gitea_api
+            .post_pull_request_review(
+                &review_result,
+                &review_payload.repository.full_name,
+                review_payload.pull_request.number,
+            )
+            .await?;
+
+        Ok(review_result)
+    }
+    .await;
+
+    let edit_msg = match bot_result {
+        Ok(bot_result) => review_result_to_markdown(&bot_result),
+        Err(e) => format!("Error while reviewing: {}", e),
+    };
+
+    gitea_api
+        .edit_comment(
+            &edit_msg,
+            &review_payload.repository.full_name,
+            new_comment.id,
+        )
+        .await?;
+
+    Ok(())
+}
+
+fn review_result_to_markdown(review_result: &ReviewResult) -> String {
+    if review_result.reviews.is_empty() {
+        return String::from("No issues found. ✅");
+    }
+
+    let mut md = String::from("## Review Feedback\n\n");
+
+    md.push_str(&format!(
+        "### {} issues found.\n\n",
+        review_result.reviews.len()
+    ));
+
+    if !review_result.comment.is_empty() {
+        md.push_str("\n---\n\n");
+        md.push_str("### Summary\n\n");
+        md.push_str(&review_result.comment);
+        md.push('\n');
+    }
+
+    if let Some(cost) = review_result.cost {
+        md.push_str("\n---\n\n");
+        md.push_str(&format!("### Cost: ${}", cost));
+        md.push('\n');
+    }
+
+    md
+}
+
+async fn download_git_diff(http_client: &reqwest::Client, url: &str) -> anyhow::Result<String> {
+    let response = http_client.get(url).send().await?;
+    let stream = response.bytes_stream().map_err(std::io::Error::other);
+
+    let mut buf = Vec::with_capacity(MAX_DIFF_SIZE);
+    StreamReader::new(stream)
+        .take((MAX_DIFF_SIZE + 1) as u64)
+        .read_to_end(&mut buf)
+        .await?;
+
+    if buf.len() > MAX_DIFF_SIZE {
+        anyhow::bail!("Git diff exceeds the maximum allowed size of 1 Mo");
+    }
+
+    Ok(String::from_utf8_lossy(&buf).into_owned())
+}
+
+fn format_diff_for_review(git_diff: &str) -> String {
+    let mut output = String::new();
+    let mut current_file: Option<&str> = None;
+    let mut new_line: u64 = 0;
+
+    for line in git_diff.lines() {
+        if let Some(rest) = line.strip_prefix("diff --git a/") {
+            if let Some(end) = rest.find(' ') {
+                current_file = Some(&rest[..end]);
+            }
+            new_line = 0;
+            continue;
+        }
+
+        if line.starts_with("---") || line.starts_with("+++") {
+            continue;
+        }
+
+        if line.starts_with("@@") && line.contains('+') {
+            if let Some(start) = parse_hunk_new_start(line) {
+                new_line = start;
+            }
+            continue;
+        }
+
+        let Some(filename) = current_file else {
+            continue;
+        };
+
+        if line.starts_with(' ') {
+            new_line += 1;
+            continue;
+        }
+
+        if let Some(code) = line.strip_prefix('+') {
+            use std::fmt::Write;
+            let _ = writeln!(output, "{filename}:{new_line}:{code}");
+            new_line += 1;
+        }
+    }
+
+    output
+}
+
+fn parse_hunk_new_start(hunk_header: &str) -> Option<u64> {
+    let plus_part = hunk_header.split('+').nth(1)?;
+    let num_str = plus_part.split(|c: char| !c.is_ascii_digit()).next()?;
+    num_str.parse::<u64>().ok()
+}
+
+#[cfg(test)]
+#[test]
+fn test_format_diff_for_review() {
+    let diff = concat!(
+        "diff --git a/src/foo.rs b/src/foo.rs\n",
+        "--- a/src/foo.rs\n",
+        "+++ b/src/foo.rs\n",
+        "@@ -1,3 +1,6 @@\n",
+        " fn main() {\n",
+        "+    let x = 1;\n",
+        "     println!(\"hello\");\n",
+        "+    let y = 2;\n",
+        "+    let z = 3;\n",
+        " }\n",
+        "diff --git a/src/bar.rs b/src/bar.rs\n",
+        "--- a/src/bar.rs\n",
+        "+++ b/src/bar.rs\n",
+        "@@ -10,4 +10,6 @@\n",
+        " old context\n",
+        "+    let a = 10;\n",
+        " more context\n",
+        "+    let b = 20;\n",
+    );
+
+    let result = format_diff_for_review(diff);
+    let expected = concat!(
+        "src/foo.rs:2:    let x = 1;\n",
+        "src/foo.rs:4:    let y = 2;\n",
+        "src/foo.rs:5:    let z = 3;\n",
+        "src/bar.rs:11:    let a = 10;\n",
+        "src/bar.rs:13:    let b = 20;\n",
+    );
+
+    assert_eq!(result, expected);
+}