From 04b82f1aa6f2aa6c3a9cebbe86e83074405fbb3f Mon Sep 17 00:00:00 2001
From: HouXiaoxuan <Hou_Xiaoxuan@163.com>
Date: Sat, 23 Dec 2023 15:43:05 +0800
Subject: [PATCH] =?UTF-8?q?merge=20ff=20=E6=9C=AA=E6=B5=8B=E8=AF=95?=
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---
 src/cli.rs            | 13 ++++++--
 src/commands/merge.rs | 72 +++++++++++++++++++++++++++++++++++++++++++
 src/commands/mod.rs   |  1 +
 3 files changed, 84 insertions(+), 2 deletions(-)
 create mode 100644 src/commands/merge.rs

diff --git a/src/cli.rs b/src/cli.rs
index b244a87..ac13a48 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -1,7 +1,7 @@
 use clap::{ArgGroup, Parser, Subcommand};
 use mit::commands::{
-    add::add, branch::branch, commit::commit, init::init, log::log, remove::remove, restore::restore, status::status,
-    switch::switch,
+    add::add, branch::branch, commit::commit, init::init, log::log, merge::merge, remove::remove, restore::restore,
+    status::status, switch::switch,
 };
 
 /// Rust实现的简易版本的Git，用于学习Rust语言
@@ -117,6 +117,12 @@ enum Command {
         #[clap(long, short = 'S', action)]
         staged: bool,
     },
+    /// merge
+    Merge {
+        /// 要合并的分支
+        #[clap(required = true)]
+        branch: String,
+    },
 }
 pub fn handle_command() {
     let cli = Cli::parse();
@@ -162,5 +168,8 @@ pub fn handle_command() {
             }
             restore(path, source.unwrap(), worktree, staged);
         }
+        Command::Merge { branch } => {
+            merge(branch);
+        }
     }
 }
diff --git a/src/commands/merge.rs b/src/commands/merge.rs
new file mode 100644
index 0000000..e258827
--- /dev/null
+++ b/src/commands/merge.rs
@@ -0,0 +1,72 @@
+use clap::builder::Str;
+
+use crate::{
+    commands, head,
+    models::{commit::Commit, object::Hash},
+    store::Store,
+    utils::util,
+};
+
+enum MergeError {
+    NoFastForward,
+}
+
+fn check_ff(current: &Hash, target: Hash) -> Result<bool, MergeError> {
+    let target_commit = Commit::load(&target);
+    // 检查current是否是target的祖先
+    if *current == target_commit.get_hash() {
+        return Ok(true);
+    }
+    for parent in target_commit.get_parent_hash() {
+        let result = check_ff(current, parent);
+        if result.is_ok() {
+            return result;
+        }
+    }
+    return Err(MergeError::NoFastForward);
+}
+
+/** commit 以fast forward到形式合并到当前分支 */
+fn merge_ff(commit_hash: String) -> Result<(), MergeError> {
+    // 检查当前分支是否可以fast forward到commit
+    let current_commit = head::current_head_commit();
+    let check = check_ff(&current_commit, commit_hash.clone());
+    if check.is_err() {
+        return Err(check.unwrap_err());
+    }
+
+    // 执行fast forward
+    let head = head::current_head();
+    match head {
+        head::Head::Branch(branch) => {
+            head::update_branch(&branch, &commit_hash.clone());
+            commands::restore::restore(vec![], commit_hash.clone(), true, true)
+        }
+        head::Head::Detached(_) => {
+            // 相当于切换到了commit_hash，什么都没有发生
+            commands::switch::switch(Some(commit_hash.clone()), None, true);
+        }
+    }
+    unimplemented!();
+}
+
+/** merge，暂时只支持fast forward */
+pub fn merge(branch: String) {
+    let merge_commit = {
+        if head::list_local_branches().contains(&branch) {
+            // Branch Name, e.g. master
+            head::get_branch_head(&branch)
+        } else {
+            // Commit Hash, e.g. a1b2c3d4
+            let store = Store::new();
+            let commit = store.search(&branch);
+            if commit.is_none() || !util::is_typeof_commit(commit.clone().unwrap()) {
+                println!("fatal: 非法的 commit hash: '{}'", branch);
+                return;
+            }
+            commit.unwrap()
+        }
+    };
+    // 暂时只支持fast forward
+    let _ = merge_ff(merge_commit);
+}
diff --git a/src/commands/mod.rs b/src/commands/mod.rs
index f9cf21c..f5c1f45 100644
--- a/src/commands/mod.rs
+++ b/src/commands/mod.rs
@@ -3,6 +3,7 @@ pub mod branch;
 pub mod commit;
 pub mod init;
 pub mod log;
+pub mod merge;
 pub mod remove;
 pub mod restore;
 pub mod status;