//! Working-copy snapshots, commits, and the change builder (spec §12.3).

use super::*;

#[derive(Clone, Copy, Debug, PartialEq, Eq)]

pub enum ChangeStatus {

    Added,

    Modified,

    Removed,

    ModeChanged,

    /// The file is conflicted in the base state and still contains conflict markers.

    ConflictEdited,

    /// The file was conflicted in the base state and the working copy resolves it.

    Resolved,

}

/// Lines that mark a conflict region in a materialized file (spec §9.5).

pub fn has_conflict_markers(content: &[u8]) -> bool {

    split_lines(content).iter().any(|l| {

        l.starts_with(b"<<<<<<< oxy conflict") || l.starts_with(b"======= oxy conflict") || l.starts_with(b">>>>>>> oxy conflict")

    })

}

#[derive(Clone, Debug, PartialEq, Eq)]

pub struct PathStatus {

    pub path: String,

    pub status: ChangeStatus,

}

/// Operations of a change built from the working directory against a base.

pub(crate) struct BuiltChange {

    pub tree_ops: Vec<TreeOp>,

    pub edits: Vec<Edit>,

    pub contributors: Vec<ChangeHash>,

    pub resolves: bool,

    pub statuses: Vec<PathStatus>,

}

/// Result of snapshotting the working copy.

pub struct SnapshotResult {

    pub wc_hash: ChangeHash,

    pub wc: Change,

    /// The base state (closure of the working-copy change's dependencies).

    pub base: State,

    pub base_snapshot: Snapshot,

    pub statuses: Vec<PathStatus>,

    /// Whether the snapshot rewrote the working-copy change.

    pub changed: bool,

    /// Whether the working copy resolves conflicts of its base (spec §9.6).

    pub resolves: bool,

    /// Changes that contributed to the conflicts being resolved.

    pub contributors: Vec<ChangeHash>,

}

pub fn is_binary(content: &[u8]) -> bool {

    content[..content.len().min(BINARY_SNIFF)].contains(&0)

}

impl Repo {

    /// Diff the files on disk against `base` and build the operations of a

    /// change from `base` to the working directory. `reuse` maps paths to the

    /// NodeIds an earlier version of the same change assigned to new paths.

    pub(crate) fn build_against(&self, base: &State, base_snapshot: &Snapshot, reuse: HashMap<String, (NodeId, NodeKind)>) -> Result<BuiltChange> {

        let fs_entries = self.walk_working_copy()?;

        self.build_from_entries(base, base_snapshot, reuse, &fs_entries)

    }

    /// Like `build_against`, for files given in memory (imports).

    pub(crate) fn build_from_entries(&self, base: &State, base_snapshot: &Snapshot, reuse: HashMap<String, (NodeId, NodeKind)>, fs_entries: &BTreeMap<String, FsEntry>) -> Result<BuiltChange> {

        let mut b = ChangeBuilder::new(base, base_snapshot, reuse);

        for (path, fs_entry) in fs_entries {

            match base_snapshot.files.get(path) {

                None => b.add_path(self, path, fs_entry)?,

                Some(expected) => b.update_path(self, path, fs_entry, expected)?,

            }

        }

        for (path, expected) in &base_snapshot.files {

            if fs_entries.contains_key(path) {

                continue;

            }

            let still_needed = expected.kind == NodeKind::Dir && fs_entries.keys().any(|p| p.starts_with(&format!("{path}/")));

            if !still_needed {

                b.remove_path(path, expected);

            }

        }

        let mut statuses = b.statuses;

        statuses.sort_by(|a, b| a.path.cmp(&b.path));

        Ok(BuiltChange { tree_ops: b.tree_ops, edits: b.edits, contributors: b.contributors.into_iter().collect(), resolves: b.resolves, statuses })

    }

    /// Store a change and, when `core.sign = change` and we are its author,

    /// sign it. A rewritten change by another author is stored unsigned: only

    /// its author (or a delegate) can vouch for it.

    pub(crate) fn store_signed(&self, change: &Change) -> Result<ChangeHash> {

        let ours = change.author == self.author();

        if self.config.sign_changes && ours && self.secret_key()?.is_none() {

            return fail("core.sign is \"change\" but no secret key is available for author.key");

        }

        let hash = self.store.put_change(change)?;

        if self.config.sign_changes && ours {

            self.sign_change(&hash)?;

        }

        Ok(hash)

    }

    /// Snapshot the working copy into the working-copy change (spec §12.3).

    pub fn snapshot(&self, command: &str) -> Result<SnapshotResult> {

        let (op_ref, op) = self.head_op()?;

        let (old_hash, old_wc) = self.working_copy()?;

        let base = self.load_state(&old_wc.deps)?;

        let base_snapshot = base.materialize();

        // Reuse the NodeIds the previous working-copy version assigned to new

        // paths, so an unchanged working copy hashes identically (spec §12.3).

        let reuse = added_node_paths(&old_wc, &base_snapshot);

        let built = self.build_against(&base, &base_snapshot, reuse)?;

        let mut wc = Change {

            change_id: old_wc.change_id,

            deps: vec![],

            author: self.author(),

            hlc: old_wc.hlc,

            message: old_wc.message.clone(),

            tree_ops: built.tree_ops,

            edits: built.edits,

            kind: ChangeKind::WorkingCopy,

        };

        let base_heads = base.maximal(&old_wc.deps);

        let mut deps: BTreeSet<ChangeHash> = base_heads.into_iter().collect();

        deps.extend(referenced_changes(&wc, &base));

        deps.extend(built.contributors.iter().copied());

        wc.deps = deps.into_iter().collect();

        wc.normalize();

        let resolves = built.resolves;

        let contributors = built.contributors;

        let statuses = built.statuses;

        // Empty snapshot: hash the candidate before storing; only record an op on change.

        let new_hash = wc.hash();

        let changed = new_hash != old_hash;

        if changed {

            self.store.put_change(&wc)?;

            let mut view = op.view.clone();

            view.workspaces.insert(self.workspace, new_hash);

            self.record_op(&[op_ref], &format!("{command}{SNAPSHOT_SUFFIX}"), view)?;

        }

        Ok(SnapshotResult { wc_hash: new_hash, wc, base, base_snapshot, statuses, changed, resolves, contributors })

    }

    /// Turn the working-copy change into a normal change on the bookmark (spec §12.3).

    pub fn commit(&self, message: &str, extra_deps: &[ChangeHash]) -> Result<ChangeHash> {

        let snap = self.snapshot("oxy commit")?;

        if snap.wc.tree_ops.is_empty() && snap.wc.edits.is_empty() {

            return fail("nothing to commit: the working copy matches its base");

        }

        if let Some(s) = snap.statuses.iter().find(|s| s.status == ChangeStatus::ConflictEdited) {

            return fail(format!("{} still contains conflict markers", s.path));

        }

        if message.trim().is_empty() {

            return fail("a commit message is required");

        }

        let (op_ref, op) = self.head_op()?;

        let mut deps: BTreeSet<ChangeHash> = referenced_changes(&snap.wc, &snap.base);

        // A resolution depends on every change that contributed to the

        // conflict (spec §8.1). Tree and opaque conflicts are resolved through

        // ordinary operations whose references already cover the contributors.

        deps.extend(snap.contributors.iter().copied());

        for d in extra_deps {

            if !snap.base.contains(d) {

                return fail(format!("--depends-on {d}: not in the working copy's base state"));

            }

            deps.insert(*d);

        }

        let mut change = Change {

            change_id: snap.wc.change_id,

            deps: deps.into_iter().collect(),

            author: self.author(),

            hlc: Hlc::now(),

            message: message.trim_end().to_string(),

            tree_ops: snap.wc.tree_ops.clone(),

            edits: snap.wc.edits.clone(),

            kind: if snap.resolves { ChangeKind::Resolution } else { ChangeKind::Normal },

        };

        change.normalize();

        let hash = self.store_signed(&change)?;

        // New bookmark heads: maximal elements of old heads plus the new change.

        // The working copy continues on its own base plus the new change, which

        // is exactly what the files on disk contain; the bookmark may hold

        // other heads (and conflicts) the working copy has not checked out.

        let old_heads = self.heads_of(&op.view, &self.config.bookmark)?;

        let old_base = snap.base.maximal(&snap.wc.deps);

        let mut all: Vec<ChangeHash> = old_heads.clone();

        all.extend(old_base.iter().copied());

        all.push(hash);

        let mut st = self.load_state(&all)?;

        st.add(change)?;

        let mut with_new = old_heads.clone();

        with_new.push(hash);

        let new_heads = st.maximal(&with_new);

        // Automatic checkpoint once enough changes accumulated (spec §11).

        let since = self.latest_checkpoint(&self.config.bookmark)?.map(|(_, cp)| cp.count).unwrap_or(0);

        if self.config.checkpoint_interval > 0 && (st.len() as u64).saturating_sub(since) >= self.config.checkpoint_interval {

            let cp_state = self.load_state_full(&new_heads)?;

            self.write_checkpoint(&self.config.bookmark, &cp_state, &new_heads)?;

        }

        let mut wc_base = old_base.clone();

        wc_base.push(hash);

        let wc_base = st.maximal(&wc_base);

        let wc = self.new_working_copy(wc_base, "");

        let wc_hash = self.store.put_change(&wc)?;

        let mut view = op.view.clone();

        view.bookmarks.insert(self.config.bookmark.clone(), self.store.put_state(&StateObject::new(new_heads))?);

        view.workspaces.insert(self.workspace, wc_hash);

        self.record_op(&[op_ref], &format!("oxy commit -m {message:?}"), view)?;

        self.maybe_autopack()?;

        Ok(hash)

    }

}

/// Builds the tree ops and edits of a working-copy change against a base.

struct ChangeBuilder<'a> {

    base: &'a State,

    base_snapshot: &'a Snapshot,

    tree_ops: Vec<TreeOp>,

    edits: Vec<Edit>,

    statuses: Vec<PathStatus>,

    dir_nodes: HashMap<String, NodeId>,

    reuse: HashMap<String, (NodeId, NodeKind)>,

    /// Changes that contributed to conflicts this working copy resolves.

    contributors: BTreeSet<ChangeHash>,

    resolves: bool,

}

impl<'a> ChangeBuilder<'a> {

    fn new(base: &'a State, base_snapshot: &'a Snapshot, reuse: HashMap<String, (NodeId, NodeKind)>) -> Self {

        let mut dir_nodes: HashMap<String, NodeId> = HashMap::new();

        dir_nodes.insert(String::new(), NodeId::ROOT);

        for (p, f) in &base_snapshot.files {

            if f.kind == NodeKind::Dir {

                dir_nodes.insert(p.clone(), f.node);

            }

        }

        ChangeBuilder { base, base_snapshot, tree_ops: vec![], edits: vec![], statuses: vec![], dir_nodes, reuse, contributors: BTreeSet::new(), resolves: false }

    }

    fn reused_node(&self, path: &str, kind: NodeKind) -> Option<NodeId> {

        self.reuse.get(path).filter(|(_, k)| *k == kind).map(|(n, _)| *n)

    }

    fn ensure_dir(&mut self, path: &str) -> NodeId {

        if let Some(n) = self.dir_nodes.get(path) {

            return *n;

        }

        let mut parent = NodeId::ROOT;

        let mut prefix = String::new();

        for comp in path.split('/') {

            if !prefix.is_empty() {

                prefix.push('/');

            }

            prefix.push_str(comp);

            parent = match self.dir_nodes.get(&prefix) {

                Some(n) => *n,

                None => {

                    let node = self.reused_node(&prefix, NodeKind::Dir).unwrap_or_else(NodeId::random);

                    self.tree_ops.push(TreeOp::AddNode { node, kind: NodeKind::Dir, mode: Mode::default(), parent, name: comp.to_string() });

                    self.dir_nodes.insert(prefix.clone(), node);

                    node

                }

            };

        }

        parent

    }

    fn add_path(&mut self, repo: &Repo, path: &str, e: &FsEntry) -> Result<()> {

        let (dir, name) = split_path(path);

        let parent = self.ensure_dir(dir);

        let node = self.reused_node(path, e.kind).unwrap_or_else(NodeId::random);

        let opaque = e.kind == NodeKind::Symlink || is_binary(&e.content);

        self.tree_ops.push(TreeOp::AddNode { node, kind: e.kind, mode: Mode { exec: e.exec, opaque }, parent, name: name.to_string() });

        if opaque {

            let blob = repo.store_blob(&e.content)?;

            self.edits.push(Edit::Replace { node, old: None, new: Some(blob) });

        } else if !e.content.is_empty() {

            self.edits.push(Edit::Insert {

                node,

                after: crate::objects::AtomRef::Start,

                before: crate::objects::AtomRef::End,

                lines: split_lines(&e.content).iter().map(|l| l.to_vec()).collect(),

            });

        }

        self.statuses.push(PathStatus { path: path.to_string(), status: ChangeStatus::Added });

        Ok(())

    }

    fn remove_path(&mut self, path: &str, expected: &crate::state::FileState) {

        let entry = &self.base_snapshot.tree.entries[path];

        self.tree_ops.push(TreeOp::RemoveNode { node: expected.node, placement: op_ref(entry.placement) });

        if path.contains(".oxy-conflict-") || expected.is_conflicted() {

            self.resolves = true;

        }

        self.statuses.push(PathStatus { path: path.to_string(), status: ChangeStatus::Removed });

    }

    fn update_path(&mut self, repo: &Repo, path: &str, e: &FsEntry, expected: &crate::state::FileState) -> Result<()> {

        if expected.kind != e.kind {

            self.remove_path(path, expected);

            self.statuses.pop();

            self.add_path(repo, path, e)?;

            self.statuses.pop();

            self.statuses.push(PathStatus { path: path.to_string(), status: ChangeStatus::Modified });

            return Ok(());

        }

        let entry = &self.base_snapshot.tree.entries[path];

        let node = expected.node;

        let mode_atom = entry.mode_atom.map(op_ref);

        let mut status: Option<ChangeStatus> = None;

        match &expected.content {

            FileContent::Dir => {}

            FileContent::Text { bytes, materialized } => {

                if materialized.is_conflicted() {

                    if bytes == &e.content {

                        return Ok(());

                    }

                    if has_conflict_markers(&e.content) {

                        self.statuses.push(PathStatus { path: path.to_string(), status: ChangeStatus::ConflictEdited });

                        return Ok(());

                    }

                    // Resolution (spec §9.6): diff against the unconflicted lines

                    // with each region as a gap, then retire every region atom.

                    // Whatever the author kept from a region is re-inserted as

                    // new atoms, which leaves the graph totally ordered.

                    let regions = self.base.conflict_regions(&node);

                    let mut edits = text_edits(node, &regions.plain, &e.content);

                    if !regions.region_atoms.is_empty() {

                        edits.insert(0, Edit::Delete { node, atoms: ranges(&regions.region_atoms) });

                    }

                    self.edits.extend(edits);

                    self.contributors.extend(regions.contributors);

                    self.resolves = true;

                    if e.exec != expected.mode.exec {

                        if let Some(old) = mode_atom {

                            self.tree_ops.push(TreeOp::SetMode { node, old, mode: Mode { exec: e.exec, opaque: false } });

                        }

                    }

                    self.statuses.push(PathStatus { path: path.to_string(), status: ChangeStatus::Resolved });

                    return Ok(());

                }

                if bytes != &e.content {

                    if is_binary(&e.content) {

                        // Text → opaque (spec §7.5).

                        if let Some(old) = mode_atom {

                            self.tree_ops.push(TreeOp::SetMode { node, old, mode: Mode { exec: e.exec, opaque: true } });

                        }

                        let live: Vec<_> = repo_live_keys(self.base, &node);

                        if !live.is_empty() {

                            self.edits.push(Edit::Delete { node, atoms: ranges(&live) });

                        }

                        let blob = repo.store_blob(&e.content)?;

                        self.edits.push(Edit::Replace { node, old: None, new: Some(blob) });

                        status = Some(ChangeStatus::Modified);

                    } else {

                        let old = self.base.live_lines(&node);

                        let edits = text_edits(node, &old, &e.content);

                        if !edits.is_empty() {

                            self.edits.extend(edits);

                            status = Some(ChangeStatus::Modified);

                        }

                    }

                }

                let switched_to_opaque = status == Some(ChangeStatus::Modified) && is_binary(&e.content);

                if !switched_to_opaque && e.exec != expected.mode.exec {

                    if let Some(old) = mode_atom {

                        self.tree_ops.push(TreeOp::SetMode { node, old, mode: Mode { exec: e.exec, opaque: false } });

                        status.get_or_insert(ChangeStatus::ModeChanged);

                    }

                }

            }

            FileContent::Opaque { blobs } => {

                let new_ref = Repo::blob_ref(&e.content);

                if blobs.len() > 1 {

                    if !blobs.contains(&new_ref) {

                        self.statuses.push(PathStatus { path: path.to_string(), status: ChangeStatus::ConflictEdited });

                    }

                    return Ok(());

                }

                let current = blobs.first().copied();

                if current != Some(new_ref) {

                    if e.kind == NodeKind::File && !is_binary(&e.content) {

                        // Opaque → text (spec §7.5).

                        if let Some(old) = mode_atom {

                            self.tree_ops.push(TreeOp::SetMode { node, old, mode: Mode { exec: e.exec, opaque: false } });

                        }

                        self.edits.push(Edit::Replace { node, old: current, new: None });

                        if !e.content.is_empty() {

                            self.edits.push(Edit::Insert {

                                node,

                                after: crate::objects::AtomRef::Start,

                                before: crate::objects::AtomRef::End,

                                lines: split_lines(&e.content).iter().map(|l| l.to_vec()).collect(),

                            });

                        }

                    } else {

                        let blob = repo.store_blob(&e.content)?;

                        self.edits.push(Edit::Replace { node, old: current, new: Some(blob) });

                    }

                    status = Some(ChangeStatus::Modified);

                } else if e.kind == NodeKind::File && e.exec != expected.mode.exec {

                    if let Some(old) = mode_atom {

                        self.tree_ops.push(TreeOp::SetMode { node, old, mode: Mode { exec: e.exec, opaque: true } });

                        status = Some(ChangeStatus::ModeChanged);

                    }

                }

            }

        }

        if let Some(s) = status {

            self.statuses.push(PathStatus { path: path.to_string(), status: s });

        }

        Ok(())

    }

}

fn repo_live_keys(base: &State, node: &NodeId) -> Vec<crate::graph::AtomKey> {

    base.live_lines(node).into_iter().map(|(k, _)| k).collect()

}

/// The changes a change's scope references (spec §8.1): introducers of every

/// atom, placement, and mode it touches, and of every node it operates on.

pub fn referenced_changes(change: &Change, base: &State) -> BTreeSet<ChangeHash> {

    let mut out = BTreeSet::new();

    let opref = |r: &OpRef, out: &mut BTreeSet<ChangeHash>| {

        if !r.change.is_zero() {

            out.insert(r.change);

        }

    };

    let mut nodes: Vec<NodeId> = Vec::new();