code-repo-wiki 0.5.0

use std::path::PathBuf;

use anyhow::{Context, Result};

/// Git diff 分析结果
#[derive(Debug, Clone, Default)]
pub struct GitDiffResult {
    /// 新增文件列表
    pub added: Vec<PathBuf>,
    /// 修改文件列表
    pub modified: Vec<PathBuf>,
    /// 删除文件列表
    pub deleted: Vec<PathBuf>,
    /// 重命名文件列表（旧路径，新路径）
    pub renamed: Vec<(PathBuf, PathBuf)>,
    /// 起始 commit hash
    pub from_commit: String,
    /// 目标 commit hash
    pub to_commit: String,
    /// 新增行数
    pub added_lines: usize,
    /// 删除行数
    pub deleted_lines: usize,
}

/// 分析 Git diff，返回变更的文件列表
///
/// 使用 git2 库分析 last_commit_hash（如有）与 HEAD 的差异。
/// 无 Git 历史或 last_commit_hash 为 None 时退化为 HEAD^。
/// 无父 commit 时返回空结果。
pub fn analyze_git_diff(repo_path: &std::path::Path, last_commit_hash: Option<&str>) -> Result<GitDiffResult> {
    let repo = git2::Repository::open(repo_path)
        .with_context(|| format!("不是 Git 仓库: {}", repo_path.display()))?;

    // 获取 HEAD commit
    let head = match repo.head() {
        Ok(h) => h,
        Err(_) => {
            tracing::info!("Git 仓库无 HEAD（空仓库或未提交）");
            return Ok(GitDiffResult::default());
        }
    };

    let head_commit = head.peel_to_commit()?;
    let head_tree = head_commit.tree()?;
    let head_oid = head_commit.id().to_string();

    // 确定 from_commit：优先使用 last_commit_hash，退化为 HEAD^
    let from_commit = if let Some(prev_hash) = last_commit_hash {
        prev_hash.to_string()
    } else if head_commit.parents().count() > 0 {
        let parent = head_commit.parent(0)?;
        parent.id().to_string()
    } else {
        tracing::info!("首次提交或无上次生成记录，无法做增量 diff");
        return Ok(GitDiffResult::default());
    };

    // 解析 from_commit 对应的 tree
    let from_obj = match repo.revparse_single(&from_commit) {
        Ok(obj) => obj,
        Err(e) => {
            tracing::warn!("无法解析 commit {}: {}，退化为空 diff", from_commit, e);
            return Ok(GitDiffResult::default());
        }
    };
    let from_tree = from_obj.peel_to_tree()?;

    let diff = repo.diff_tree_to_tree(Some(&from_tree), Some(&head_tree), None)?;

    let mut result = GitDiffResult {
        from_commit,
        to_commit: head_oid,
        ..Default::default()
    };

    diff.foreach(
        &mut |delta, _| {
            let new_file = delta.new_file();
            let old_file = delta.old_file();

            match delta.status() {
                git2::Delta::Added => {
                    if let Some(path) = new_file.path() {
                        result.added.push(path.to_path_buf());
                    }
                }
                git2::Delta::Deleted => {
                    if let Some(path) = old_file.path() {
                        result.deleted.push(path.to_path_buf());
                    }
                }
                git2::Delta::Modified => {
                    if let Some(path) = new_file.path() {
                        result.modified.push(path.to_path_buf());
                    }
                }
                git2::Delta::Renamed => {
                    let old = old_file.path().map(|p| p.to_path_buf());
                    let new = new_file.path().map(|p| p.to_path_buf());
                    if let (Some(old), Some(new)) = (old, new) {
                        result.renamed.push((old, new));
                    }
                }
                _ => {}
            }
            true
        },
        None,
        None,
        None,
    )?;

    // 统计整个 diff 的新增/删除行数（DiffDelta 无行级统计 API，用 Diff 级 stats）
    let stats = diff.stats()?;
    result.added_lines = stats.insertions();
    result.deleted_lines = stats.deletions();

    Ok(result)
}


/// 在指定项目根下获取当前 HEAD commit hash
///
/// git 仓库定位基准显式注入：不再依赖进程 cwd（watch 常驻进程的
/// cwd 漂移不再改变仓库解析目标）。
pub fn get_head_commit_hash_at(root: &crate::project::ProjectRoot) -> Result<String> {
    let repo = git2::Repository::open(root.path())?;
    let head = repo.head()?;
    let oid = head.target().ok_or_else(|| anyhow::anyhow!("HEAD 没有目标"))?;
    Ok(oid.to_string())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_git_diff_result_default() {
        let result = GitDiffResult::default();
        assert!(result.added.is_empty());
        assert!(result.modified.is_empty());
        assert!(result.deleted.is_empty());
        assert!(result.renamed.is_empty());
        assert!(result.from_commit.is_empty());
        assert!(result.to_commit.is_empty());
    }

    #[test]
    fn test_analyze_git_diff_non_repo() {
        let tmp = std::env::temp_dir().join("code-repo-wiki-test-diff-nonexistent");
        let result = analyze_git_diff(&tmp, None);

        // 非 Git 仓库应返回 Err
        assert!(result.is_err());
    }

    /// 在临时仓库中做 2 次提交，验证 diff 行数统计正确
    #[test]
    fn test_diff_line_stats() {
        let dir = std::env::temp_dir().join(format!("code_repo_wiki_test_diff_stats_{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&dir);
        let repo = git2::Repository::init(&dir).unwrap();
        let mut cfg = repo.config().unwrap();
        cfg.set_str("user.name", "test").unwrap();
        cfg.set_str("user.email", "test@test.com").unwrap();

        std::fs::write(dir.join("a.txt"), "line1\nline2\n").unwrap();
        let first = add_and_commit(&repo, "init");

        // 第二次提交：新增 2 行
        std::fs::write(dir.join("a.txt"), "line1\nline2\nline3\nline4\n").unwrap();
        add_and_commit(&repo, "add two lines");

        let result = analyze_git_diff(&dir, Some(&first)).unwrap();
        assert_eq!(result.added_lines, 2);
        assert_eq!(result.deleted_lines, 0);

        // 第三次提交：删除 1 行
        std::fs::write(dir.join("a.txt"), "line1\nline3\nline4\n").unwrap();
        add_and_commit(&repo, "del one line");

        let second = repo.revparse_single("HEAD^").unwrap().peel_to_commit().unwrap();
        let result = analyze_git_diff(&dir, Some(&second.id().to_string())).unwrap();
        assert_eq!(result.added_lines, 0);
        assert_eq!(result.deleted_lines, 1);

        let _ = std::fs::remove_dir_all(&dir);
    }

    /// 提交当前工作区全部文件并返回 commit id
    fn add_and_commit(repo: &git2::Repository, message: &str) -> String {
        let mut index = repo.index().unwrap();
        index.add_all(["*"], git2::IndexAddOption::DEFAULT, None).unwrap();
        index.write().unwrap();
        let tree_id = index.write_tree().unwrap();
        let tree = repo.find_tree(tree_id).unwrap();
        let sig = git2::Signature::now("test", "test@test.com").unwrap();
        let commit_id = match repo.head().ok() {
            Some(head) => {
                let parent = head.peel_to_commit().unwrap();
                repo.commit(Some("HEAD"), &sig, &sig, message, &tree, &[&parent]).unwrap()
            }
            None => repo.commit(Some("HEAD"), &sig, &sig, message, &tree, &[]).unwrap(),
        };
        commit_id.to_string()
    }
}