use serde::Deserialize;
use crate::error::{Error, Result};
pub mod prompt {
use crate::cli::PrSource;
use crate::commit_msg::prompt::ChatMessage;
const SOURCE_CHAR_LIMIT: usize = 32_000;
const SYSTEM_PROMPT_PREFIX: &str = "\
You are a senior engineer writing GitHub pull request text.
Respond with ONLY compact JSON — no prose before or after, no code fences, no
quoting outside JSON.
Required JSON shape:
{
\"title\": \"short imperative PR title\",
\"body\": \"Markdown PR body\"
}
";
const PREDEFINED_RULES: &str = "\
- title: imperative mood, no trailing period, ≤ 72 chars
- body: Markdown. Treat it as a mini architecture note that helps reviewers
answer: \"What am I reviewing, why does it matter, and where should I focus?\"
- a PR message is different from a commit message: a commit explains one
change; a PR explains the whole story
- include these sections, omitting only sections that truly do not apply:
## Summary
## Context
## Changes
## Trade-offs / Risks
## Testing
## Screenshots / Demo
## References
- Summary: explain what this PR changes at a high level
- Context: explain why the PR exists and what problem it solves
- Changes: describe key implementation points, not every file changed
- Trade-offs / Risks: call out limitations, migration notes, review risks, and
behavior that old clients/users keep
- Testing: list only verification shown by the input; if none is visible, say
\"Not run (not shown in input)\"
- Screenshots / Demo: include for UI-visible changes when the input supports it
- References: include only issues, incidents, docs, or links present in input
- describe HOW when implementation is non-trivial, reviewers need guidance,
there are architectural decisions/trade-offs, the diff is large, the PR
touches multiple layers, or future development is affected
- Avoid HOW when it only repeats the file diff
- bad HOW: \"Changed `order.ts`; updated `api.ts`; added `utils.ts`\"
- good HOW: \"Centralizes retry handling in the request layer so individual API
calls do not need their own retry logic\"
- do not invent tickets, reviewers, labels, or test results not present in the input
";
pub fn build(
source: PrSource,
base: &str,
text: &str,
custom_rules: Option<&str>,
) -> Vec<ChatMessage> {
let source_label = match source {
PrSource::Diff => "Branch diff",
PrSource::Commits => "Commit log",
};
vec![
ChatMessage::system(system_prompt(custom_rules)),
ChatMessage::user(format!(
"Base branch: {base}\nSource: {source_label}\n\n```text\n{}\n```",
truncate(text)
)),
]
}
fn system_prompt(custom_rules: Option<&str>) -> String {
let rules = custom_rules.unwrap_or(PREDEFINED_RULES);
format!("{SYSTEM_PROMPT_PREFIX}Rules:\n{rules}")
}
fn truncate(text: &str) -> String {
if text.len() <= SOURCE_CHAR_LIMIT {
return text.to_string();
}
let mut end = SOURCE_CHAR_LIMIT;
while !text.is_char_boundary(end) {
end -= 1;
}
let mut out = String::with_capacity(end + 64);
out.push_str(&text[..end]);
out.push_str("\n\n# ... PR source truncated to ");
out.push_str(&end.to_string());
out.push_str(" bytes ...\n");
out
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn build_mentions_commit_log_source() {
let messages = build(PrSource::Commits, "main", "feat: add PR flow", None);
assert!(messages[1].content.contains("Base branch: main"));
assert!(messages[1].content.contains("Source: Commit log"));
assert!(messages[1].content.contains("feat: add PR flow"));
}
#[test]
fn build_uses_custom_rules_in_predefined_system_prompt() {
let messages = build(
PrSource::Diff,
"main",
"diff --git a/x b/x",
Some("- custom PR rule\n"),
);
assert!(messages[0].content.contains("Required JSON shape"));
assert!(messages[0].content.contains("Rules:\n- custom PR rule\n"));
assert!(!messages[0].content.contains("- title: imperative mood"));
assert!(messages[1].content.contains("Source: Branch diff"));
}
#[test]
fn build_uses_predefined_rules_by_default() {
let messages = build(PrSource::Diff, "main", "diff --git a/x b/x", None);
assert!(messages[0]
.content
.contains("Rules:\n- title: imperative mood"));
assert!(messages[0].content.contains("- include these sections"));
}
#[test]
fn system_prompt_requests_review_story_sections() {
let messages = build(PrSource::Diff, "main", "diff --git a/x b/x", None);
let system = &messages[0].content;
for section in [
"## Summary",
"## Context",
"## Changes",
"## Trade-offs / Risks",
"## Testing",
"## Screenshots / Demo",
"## References",
] {
assert!(system.contains(section), "missing section: {section}");
}
assert!(system.contains("mini architecture note"));
assert!(system.contains("Avoid HOW when it only repeats the file diff"));
}
}
}
#[derive(Debug, PartialEq, Eq)]
pub struct PullRequestMessage {
pub title: String,
pub body: String,
}
#[derive(Debug, Deserialize)]
struct RawPullRequestMessage {
title: String,
body: String,
}
pub fn parse_json(raw: &str) -> Result<PullRequestMessage> {
let raw = crate::commit_msg::strip_code_fences(raw);
let msg: RawPullRequestMessage = serde_json::from_str(&raw)?;
let title = msg.title.trim().to_string();
let body = msg.body.trim().to_string();
if title.is_empty() {
return Err(Error::Config("PR title cannot be empty".to_string()));
}
if body.is_empty() {
return Err(Error::Config("PR body cannot be empty".to_string()));
}
Ok(PullRequestMessage { title, body })
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn parses_pr_message_json() {
let msg =
parse_json(r###"{"title":"Add PR drafts","body":"## Summary\n- adds PR flow"}"###)
.unwrap();
assert_eq!(
msg,
PullRequestMessage {
title: "Add PR drafts".to_string(),
body: "## Summary\n- adds PR flow".to_string(),
}
);
}
#[test]
fn parses_fenced_pr_message_json() {
let msg = parse_json(
"```json\n{\"title\":\"Add PR drafts\",\"body\":\"## Summary\\n- adds PR flow\"}\n```",
)
.unwrap();
assert_eq!(msg.title, "Add PR drafts");
assert!(msg.body.contains("adds PR flow"));
}
#[test]
fn rejects_empty_pr_title() {
let err = parse_json(r#"{"title":" ","body":"body"}"#).unwrap_err();
assert!(matches!(err, Error::Config(msg) if msg == "PR title cannot be empty"));
}
}