//! 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)?;
        }
        // The prompt compares against this without recording anything.
        self.write_manifest(base_snapshot.is_conflicted(), !wc.tree_ops.is_empty() || !wc.edits.is_empty())?;
        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.write_manifest(snap.base_snapshot.is_conflicted() && !snap.resolves, false)?;
        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();
    for op in &change.tree_ops {
        match op {
            TreeOp::AddNode { parent, .. } => nodes.push(*parent),
            TreeOp::RemoveNode { node, placement } => {
                nodes.push(*node);
                opref(placement, &mut out);
            }
            TreeOp::Move { node, old, parent, .. } => {
                nodes.push(*node);
                nodes.push(*parent);
                opref(old, &mut out);
            }
            TreeOp::SetMode { node, old, .. } => {
                nodes.push(*node);
                opref(old, &mut out);
            }
        }
    }
    for e in &change.edits {
        nodes.push(e.node());
        match e {
            Edit::Insert { after, before, .. } => {
                for r in [after, before] {
                    if let crate::objects::AtomRef::Atom { change, .. } = r {
                        if !change.is_zero() {
                            out.insert(*change);
                        }
                    }
                }
            }
            Edit::Delete { atoms, .. } => {
                for r in atoms {
                    if !r.change.is_zero() {
                        out.insert(r.change);
                    }
                }
            }
            Edit::Replace { .. } => {}
        }
    }
    for n in nodes {
        if let Some(h) = base.tree().introducer(&n) {
            out.insert(h);
        }
    }
    out
}

/// Paths of the nodes a change adds on top of `base_snapshot`.
pub fn added_node_paths(change: &Change, base_snapshot: &Snapshot) -> HashMap<String, (NodeId, NodeKind)> {
    let by_node = base_snapshot.tree.by_node();
    let mut new_names: HashMap<NodeId, (NodeId, String, NodeKind)> = HashMap::new();
    for op in &change.tree_ops {
        if let TreeOp::AddNode { node, parent, name, kind, .. } = op {
            new_names.insert(*node, (*parent, name.clone(), *kind));
        }
    }
    let mut out = HashMap::new();
    for (node, (_, _, kind)) in &new_names {
        if let Some(path) = path_of_node(node, &by_node, &new_names) {
            out.insert(path, (*node, *kind));
        }
    }
    out
}

fn path_of_node(
    n: &NodeId,
    by_node: &HashMap<NodeId, &crate::tree::TreeEntry>,
    new_names: &HashMap<NodeId, (NodeId, String, NodeKind)>,
) -> Option<String> {
    if let Some(e) = by_node.get(n) {
        return Some(e.path.clone());
    }
    let mut parts = Vec::new();
    let mut cur = *n;
    loop {
        if cur.is_root() {
            break;
        }
        if let Some(e) = by_node.get(&cur) {
            if !e.path.is_empty() {
                parts.push(e.path.clone());
            }
            break;
        }
        let (parent, name, _) = new_names.get(&cur)?;
        parts.push(name.clone());
        cur = *parent;
    }
    parts.reverse();
    Some(parts.join("/"))
}

/// Render a change's operations with line content, using `base` for deleted lines.
pub fn render_change(change: &Change, base: &State, base_snapshot: &Snapshot) -> String {
    let by_node = base_snapshot.tree.by_node();
    let mut new_names: HashMap<NodeId, (NodeId, String, NodeKind)> = HashMap::new();
    for op in &change.tree_ops {
        if let TreeOp::AddNode { node, parent, name, kind, .. } = op {
            new_names.insert(*node, (*parent, name.clone(), *kind));
        }
    }
    let path_of = |n: &NodeId| -> String { path_of_node(n, &by_node, &new_names).unwrap_or_else(|| format!("<node {}>", n.short(8))) };

    let mut out = String::new();
    for op in &change.tree_ops {
        match op {
            TreeOp::AddNode { node, kind, mode, .. } => {
                out.push_str(&format!("A {} ({:?}{}{})\n", path_of(node), kind, if mode.exec { ", exec" } else { "" }, if mode.opaque { ", opaque" } else { "" }));
            }
            TreeOp::RemoveNode { node, .. } => out.push_str(&format!("D {}\n", path_of(node))),
            TreeOp::Move { node, name, .. } => out.push_str(&format!("R {} -> {}\n", path_of(node), name)),
            TreeOp::SetMode { node, mode, .. } => {
                out.push_str(&format!("M {} mode: exec={} opaque={}\n", path_of(node), mode.exec, mode.opaque));
            }
        }
    }
    let mut last_node: Option<NodeId> = None;
    for e in &change.edits {
        let n = e.node();
        if last_node != Some(n) {
            out.push_str(&format!("--- {}\n", path_of(&n)));
            last_node = Some(n);
        }
        match e {
            Edit::Insert { lines, .. } => {
                for l in lines {
                    out.push('+');
                    out.push_str(&String::from_utf8_lossy(l));
                    if !l.ends_with(b"\n") {
                        out.push('\n');
                    }
                }
            }
            Edit::Delete { atoms, .. } => {
                for r in atoms {
                    for i in r.from..r.to {
                        let content = base.file(&n).and_then(|g| g.content(&(r.change, i))).unwrap_or(b"<unknown>\n");
                        out.push('-');
                        out.push_str(&String::from_utf8_lossy(content));
                        if !content.ends_with(b"\n") {
                            out.push('\n');
                        }
                    }
                }
            }
            Edit::Replace { old, new, .. } => {
                out.push_str(&format!(
                    "  opaque content {} -> {}\n",
                    old.map(|o| o.short(12)).unwrap_or_else(|| "none".into()),
                    new.map(|o| o.short(12)).unwrap_or_else(|| "none".into())
                ));
            }
        }
    }
    out
}