4 files changed, 276 insertions, 0 deletions

diff --git a/src/bin/ngit/cli.rs b/src/bin/ngit/cli.rs
index 47f4b27..5c1a097 100644
--- a/src/bin/ngit/cli.rs
+++ b/src/bin/ngit/cli.rs
@@ -106,6 +106,11 @@ pub enum Commands {
     Send(sub_commands::send::SubCommandArgs),
     /// list PRs; checkout, apply or download selected
     List,
+    /// checkout a proposal branch by event-id or nevent
+    Checkout {
+        /// Proposal event-id (hex) or nevent (bech32)
+        id: String,
+    },
     /// update repo git servers to reflect nostr state (add, update or delete
     /// remote refs)
     Sync(sub_commands::sync::SubCommandArgs),
diff --git a/src/bin/ngit/main.rs b/src/bin/ngit/main.rs
index b6b51d0..2c9e10f 100644
--- a/src/bin/ngit/main.rs
+++ b/src/bin/ngit/main.rs
@@ -53,6 +53,7 @@ async fn main() {
             }
             Commands::Send(args) => sub_commands::send::launch(&cli, args, false).await,
             Commands::Sync(args) => sub_commands::sync::launch(args).await,
+            Commands::Checkout { id } => sub_commands::checkout::launch(id).await,
         }
     } else {
         // Handle the case where no command is provided
diff --git a/src/bin/ngit/sub_commands/checkout.rs b/src/bin/ngit/sub_commands/checkout.rs
new file mode 100644
index 0000000..0df1134
--- /dev/null
+++ b/src/bin/ngit/sub_commands/checkout.rs
@@ -0,0 +1,269 @@
+use std::collections::HashSet;
+
+use anyhow::{Context, Result, bail};
+use ngit::{
+    client::{
+        Params, get_all_proposal_patch_pr_pr_update_events_from_cache,
+        get_proposals_and_revisions_from_cache,
+    },
+    fetch::fetch_from_git_server,
+    git_events::{
+        KIND_PULL_REQUEST, KIND_PULL_REQUEST_UPDATE, get_commit_id_from_patch,
+        get_pr_tip_event_or_most_recent_patch_with_ancestors, tag_value,
+    },
+    repo_ref::{RepoRef, is_grasp_server_in_list},
+};
+use nostr::nips::nip19::Nip19;
+use nostr_sdk::{EventId, FromBech32};
+
+use crate::{
+    client::{Client, Connect, fetching_with_report, get_repo_ref_from_cache},
+    git::{Repo, RepoActions, str_to_sha1},
+    git_events::{event_to_cover_letter, patch_supports_commit_ids},
+    repo_ref::get_repo_coordinates_when_remote_unknown,
+};
+
+pub async fn launch(id: &str) -> Result<()> {
+    let event_id = parse_event_id(id)?;
+
+    let git_repo = Repo::discover().context("failed to find a git repository")?;
+    let git_repo_path = git_repo.get_path()?;
+
+    let client = Client::new(Params::with_git_config_relay_defaults(&Some(&git_repo)));
+
+    let repo_coordinates = get_repo_coordinates_when_remote_unknown(&git_repo, &client).await?;
+
+    fetching_with_report(git_repo_path, &client, &repo_coordinates).await?;
+
+    let repo_ref = get_repo_ref_from_cache(Some(git_repo_path), &repo_coordinates).await?;
+
+    let proposals_and_revisions: Vec<nostr::Event> =
+        get_proposals_and_revisions_from_cache(git_repo_path, repo_ref.coordinates()).await?;
+
+    let proposal = proposals_and_revisions
+        .iter()
+        .find(|e| e.id == event_id)
+        .context(format!("proposal with id {} not found in cache", event_id.to_hex()))?;
+
+    let cover_letter = event_to_cover_letter(proposal)
+        .context("failed to extract proposal details from proposal root event")?;
+
+    let commits_events: Vec<nostr::Event> = get_all_proposal_patch_pr_pr_update_events_from_cache(
+        git_repo_path,
+        &repo_ref,
+        &proposal.id,
+    )
+    .await?;
+
+    let most_recent_proposal_patch_chain_or_pr_or_pr_update =
+        get_pr_tip_event_or_most_recent_patch_with_ancestors(commits_events.clone())
+            .context("failed to find any PR or patch events on this proposal")?;
+
+    if most_recent_proposal_patch_chain_or_pr_or_pr_update
+        .iter()
+        .any(|e| [KIND_PULL_REQUEST, KIND_PULL_REQUEST_UPDATE].contains(&e.kind))
+    {
+        checkout_pr(
+            &git_repo,
+            &repo_ref,
+            &cover_letter,
+            &most_recent_proposal_patch_chain_or_pr_or_pr_update,
+        )
+    } else {
+        checkout_patch(
+            &git_repo,
+            &cover_letter,
+            &most_recent_proposal_patch_chain_or_pr_or_pr_update,
+        )
+    }
+}
+
+fn parse_event_id(id: &str) -> Result<EventId> {
+    if let Ok(nip19) = Nip19::from_bech32(id) {
+        match nip19 {
+            Nip19::Event(e) => return Ok(e.event_id),
+            Nip19::EventId(event_id) => return Ok(event_id),
+            _ => {}
+        }
+    }
+    if let Ok(event_id) = EventId::from_hex(id) {
+        return Ok(event_id);
+    }
+    bail!("invalid event-id or nevent: {id}")
+}
+
+fn checkout_pr(
+    git_repo: &Repo,
+    repo_ref: &RepoRef,
+    cover_letter: &crate::git_events::CoverLetter,
+    most_recent_proposal_patch_chain_or_pr_or_pr_update: &[nostr::Event],
+) -> Result<()> {
+    let branch_name = cover_letter.get_branch_name_with_pr_prefix_and_shorthand_id()?;
+    let local_branch_tip = git_repo.get_tip_of_branch(&branch_name).ok();
+    let proposal_tip_event = most_recent_proposal_patch_chain_or_pr_or_pr_update
+        .first()
+        .context("most_recent_proposal_patch_chain_or_pr_or_pr_update will always contain an event with c tag")?;
+    let proposal_tip = tag_value(proposal_tip_event, "c")?;
+
+    if let Some(local_branch_tip) = local_branch_tip {
+        git_repo
+            .checkout(&branch_name)
+            .context("cannot checkout existing proposal branch")?;
+        if local_branch_tip.to_string() == proposal_tip {
+            println!("checked out up-to-date proposal branch '{branch_name}'");
+            return Ok(());
+        }
+        if git_repo.does_commit_exist(&proposal_tip)? {
+            git_repo.create_branch_at_commit(&branch_name, &proposal_tip)?;
+            git_repo.checkout(&branch_name)?;
+            println!("checked out proposal branch and updated tip '{branch_name}'");
+            return Ok(());
+        }
+    }
+
+    fetch_oid_for_from_servers_for_pr(
+        &proposal_tip,
+        git_repo,
+        repo_ref,
+        proposal_tip_event,
+    )?;
+    git_repo.create_branch_at_commit(&branch_name, &proposal_tip)?;
+    git_repo.checkout(&branch_name)?;
+    if local_branch_tip.is_some() {
+        println!("checked out proposal branch and pulled updates '{branch_name}'");
+    } else {
+        println!("created and checked out proposal branch '{branch_name}'");
+    }
+    Ok(())
+}
+
+fn checkout_patch(
+    git_repo: &Repo,
+    cover_letter: &crate::git_events::CoverLetter,
+    most_recent_proposal_patch_chain_or_pr_or_pr_update: &[nostr::Event],
+) -> Result<()> {
+    let no_support_for_patches_as_branch = most_recent_proposal_patch_chain_or_pr_or_pr_update
+        .iter()
+        .any(|event| !patch_supports_commit_ids(event));
+
+    if no_support_for_patches_as_branch {
+        bail!(
+            "this proposal cannot be checked out as a branch because some patches do not have a parent commit.\n\
+             Try `ngit apply --stdout` to apply patches to the current branch, or use `ngit list` for interactive options."
+        );
+    }
+
+    let proposal_base_commit = str_to_sha1(&tag_value(
+        most_recent_proposal_patch_chain_or_pr_or_pr_update
+            .last()
+            .context("there should be at least one patch")?,
+        "parent-commit",
+    )?)
+    .context("failed to get valid parent commit id from patch")?;
+
+    let (main_branch_name, _master_tip) = git_repo.get_main_or_master_branch()?;
+
+    if !git_repo.does_commit_exist(&proposal_base_commit.to_string())? {
+        bail!(
+            "the proposal parent commit doesn't exist in your local repository.\n\
+             Try running `git pull` on '{main_branch_name}' first, or use `ngit apply --stdout` to apply patches to the current branch."
+        );
+    }
+
+    if git_repo.has_outstanding_changes()? {
+        bail!(
+            "working directory is not clean. Discard or stash (un)staged changes and try again."
+        );
+    }
+
+    let branch_name = cover_letter.get_branch_name_with_pr_prefix_and_shorthand_id()?;
+    let branch_exists = git_repo
+        .get_local_branch_names()
+        .context("failed to get local branch names")?
+        .iter()
+        .any(|n| n.eq(&branch_name));
+
+    if !branch_exists {
+        let _ = git_repo
+            .apply_patch_chain(&branch_name, most_recent_proposal_patch_chain_or_pr_or_pr_update.to_vec())
+            .context("failed to apply patch chain")?;
+        println!("checked out proposal as '{branch_name}' branch");
+        return Ok(());
+    }
+
+    let local_branch_tip = git_repo.get_tip_of_branch(&branch_name)?;
+
+    let proposal_tip = str_to_sha1(
+        &get_commit_id_from_patch(
+            most_recent_proposal_patch_chain_or_pr_or_pr_update
+                .first()
+                .context("there should be at least one patch")?,
+        )
+        .context("failed to get valid commit_id from patch")?,
+    )
+    .context("failed to get valid commit_id from patch")?;
+
+    if proposal_tip.eq(&local_branch_tip) {
+        git_repo.checkout(&branch_name)?;
+        println!("branch '{branch_name}' checked out and up-to-date");
+        return Ok(());
+    }
+
+    git_repo.create_branch_at_commit(&branch_name, &proposal_base_commit.to_string())?;
+    git_repo.checkout(&branch_name)?;
+    let _ = git_repo
+        .apply_patch_chain(&branch_name, most_recent_proposal_patch_chain_or_pr_or_pr_update.to_vec())
+        .context("failed to apply patch chain")?;
+    println!("checked out updated proposal as '{branch_name}' branch");
+    Ok(())
+}
+
+fn fetch_oid_for_from_servers_for_pr(
+    oid: &str,
+    git_repo: &Repo,
+    repo_ref: &RepoRef,
+    pr_or_pr_update_event: &nostr::Event,
+) -> Result<()> {
+    let git_servers = {
+        let mut seen: HashSet<String> = HashSet::new();
+        let mut out: Vec<String> = vec![];
+        for tag in pr_or_pr_update_event.tags.as_slice() {
+            if tag.kind().eq(&nostr::event::TagKind::Clone) {
+                for clone_url in tag.as_slice().iter().skip(1) {
+                    seen.insert(clone_url.clone());
+                }
+            }
+        }
+        for server in &repo_ref.git_server {
+            if seen.insert(server.clone()) {
+                out.push(server.clone());
+            }
+        }
+        out
+    };
+
+    let mut errors = vec![];
+    let term = console::Term::stderr();
+
+    for git_server_url in &git_servers {
+        if let Err(error) = fetch_from_git_server(
+            git_repo,
+            &[oid.to_string()],
+            git_server_url,
+            &repo_ref.to_nostr_git_url(&None),
+            &term,
+            is_grasp_server_in_list(git_server_url, &repo_ref.grasp_servers()),
+        ) {
+            errors.push(error);
+        } else {
+            println!("fetched proposal git data from {git_server_url}");
+            break;
+        }
+    }
+    if !git_repo.does_commit_exist(oid)? {
+        bail!(
+            "cannot find proposal git data from proposal git server hint or repository git servers"
+        )
+    }
+    Ok(())
+}
diff --git a/src/bin/ngit/sub_commands/mod.rs b/src/bin/ngit/sub_commands/mod.rs
index 9c84ef2..e9f91db 100644
--- a/src/bin/ngit/sub_commands/mod.rs
+++ b/src/bin/ngit/sub_commands/mod.rs
@@ -1,3 +1,4 @@
+pub mod checkout;
 pub mod create;
 pub mod export_keys;
 pub mod init;