//! Operation log objects (spec §12.1): every mutation of local repository
//! state records an `Op` whose `view` is the complete set of references and
//! workspaces afterwards.
//!
//! Encoding: `bookmarks` is an array of `[name, state_ref]` sorted by name and
//! `workspaces` an array of `[workspace_id, change_hash]` sorted by id, since
//! canonical maps carry only integer keys. Repository format 1 encoded a
//! bookmark as `[name, [heads]]`; `Op::decode_format1` reads that for migration.

use crate::cbor::{self, Value};
use crate::hash::{hash_object, ChangeHash, ObjectRef, ObjectType};
use crate::ids::WorkspaceId;
use crate::objects::{
    array, bytes, check_version, field, oref, text, Hlc, ObjectError, FORMAT_VERSION,
};
use std::collections::BTreeMap;

#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct View {
    /// Bookmark name → ObjectRef of a `state` object (spec §10.1).
    pub bookmarks: BTreeMap<String, ObjectRef>,
    pub workspaces: BTreeMap<WorkspaceId, ChangeHash>,
    /// `remotes/<remote>/bookmarks/<name>`: remote → bookmark → state ObjectRef.
    pub remotes: BTreeMap<String, BTreeMap<String, ObjectRef>>,
    /// The `policy` reference (spec §10.1, §14.5): ObjectRef of the current policy.
    pub policy: Option<ObjectRef>,
    /// `tags/<name>`: immutable states (spec §10.1).
    pub tags: BTreeMap<String, ObjectRef>,
}

/// A format-1 view, only produced by `Op::decode_format1`.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct Format1View {
    pub bookmarks: BTreeMap<String, Vec<ChangeHash>>,
    pub workspaces: BTreeMap<WorkspaceId, ChangeHash>,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Op {
    pub parents: Vec<ObjectRef>,
    pub hlc: Hlc,
    pub command: String,
    pub view: View,
    /// The workspace whose command recorded it (oxygen#99); absent in
    /// operations written before it was kept.
    pub workspace: Option<WorkspaceId>,
    /// For an undo that reverted an older operation in place: that
    /// operation, so a further undo goes on past it.
    pub undoes: Option<ObjectRef>,
}

impl View {
    fn to_value(&self) -> Value {
        Value::map([
            (
                0,
                Value::Array(
                    self.bookmarks
                        .iter()
                        .map(|(n, st)| {
                            Value::Array(vec![Value::Text(n.clone()), Value::Bytes(st.0.to_vec())])
                        })
                        .collect(),
                ),
            ),
            (
                1,
                Value::Array(
                    self.workspaces
                        .iter()
                        .map(|(w, h)| {
                            Value::Array(vec![
                                Value::Bytes(w.0.to_vec()),
                                Value::Bytes(h.0.to_vec()),
                            ])
                        })
                        .collect(),
                ),
            ),
            (
                2,
                Value::Array(
                    self.remotes
                        .iter()
                        .map(|(r, bms)| {
                            Value::Array(vec![
                                Value::Text(r.clone()),
                                Value::Array(
                                    bms.iter()
                                        .map(|(n, st)| {
                                            Value::Array(vec![
                                                Value::Text(n.clone()),
                                                Value::Bytes(st.0.to_vec()),
                                            ])
                                        })
                                        .collect(),
                                ),
                            ])
                        })
                        .collect(),
                ),
            ),
            (
                3,
                self.policy
                    .map(|p| Value::Bytes(p.0.to_vec()))
                    .unwrap_or(Value::Null),
            ),
            (
                4,
                Value::Array(
                    self.tags
                        .iter()
                        .map(|(n, st)| {
                            Value::Array(vec![Value::Text(n.clone()), Value::Bytes(st.0.to_vec())])
                        })
                        .collect(),
                ),
            ),
        ])
    }

    fn from_value(v: &Value) -> Result<View, ObjectError> {
        let m = v
            .as_map()
            .ok_or_else(|| ObjectError::Schema("view: expected map".into()))?;
        let mut view = View::default();
        for b in array(field(m, 0, "bookmarks")?, "bookmarks")? {
            let pair = array(b, "bookmark")?;
            if pair.len() != 2 {
                return Err(ObjectError::Schema(
                    "bookmark: expected [name, heads]".into(),
                ));
            }
            let name = text(&pair[0], "bookmark name")?.to_owned();
            view.bookmarks
                .insert(name, oref(&pair[1], "bookmark state")?);
        }
        view.workspaces = workspaces_from_value(field(m, 1, "workspaces")?)?;
        if let Some(rs) = m.get(&2) {
            for r in array(rs, "remotes")? {
                let pair = array(r, "remote")?;
                if pair.len() != 2 {
                    return Err(ObjectError::Schema(
                        "remote: expected [name, bookmarks]".into(),
                    ));
                }
                let name = text(&pair[0], "remote name")?.to_owned();
                let mut bms = BTreeMap::new();
                for b in array(&pair[1], "remote bookmarks")? {
                    let bp = array(b, "remote bookmark")?;
                    if bp.len() != 2 {
                        return Err(ObjectError::Schema(
                            "remote bookmark: expected [name, state]".into(),
                        ));
                    }
                    bms.insert(
                        text(&bp[0], "bookmark name")?.to_owned(),
                        oref(&bp[1], "bookmark state")?,
                    );
                }
                view.remotes.insert(name, bms);
            }
        }
        if let Some(p) = m.get(&3) {
            view.policy = if p.is_null() {
                None
            } else {
                Some(oref(p, "policy")?)
            };
        }
        if let Some(ts) = m.get(&4) {
            for t in array(ts, "tags")? {
                let pair = array(t, "tag")?;
                if pair.len() != 2 {
                    return Err(ObjectError::Schema("tag: expected [name, state]".into()));
                }
                view.tags.insert(
                    text(&pair[0], "tag name")?.to_owned(),
                    oref(&pair[1], "tag state")?,
                );
            }
        }
        Ok(view)
    }
}

fn workspaces_from_value(v: &Value) -> Result<BTreeMap<WorkspaceId, ChangeHash>, ObjectError> {
    let mut out = BTreeMap::new();
    for w in array(v, "workspaces")? {
        let pair = array(w, "workspace")?;
        if pair.len() != 2 {
            return Err(ObjectError::Schema(
                "workspace: expected [id, change]".into(),
            ));
        }
        let id = WorkspaceId::from_slice(bytes(&pair[0], "workspace id")?)
            .ok_or_else(|| ObjectError::Schema("workspace id: expected 16 bytes".into()))?;
        out.insert(id, oref(&pair[1], "workspace change")?);
    }
    Ok(out)
}

impl Format1View {
    fn from_value(v: &Value) -> Result<Format1View, ObjectError> {
        let m = v
            .as_map()
            .ok_or_else(|| ObjectError::Schema("view: expected map".into()))?;
        let mut view = Format1View::default();
        for b in array(field(m, 0, "bookmarks")?, "bookmarks")? {
            let pair = array(b, "bookmark")?;
            if pair.len() != 2 {
                return Err(ObjectError::Schema(
                    "bookmark: expected [name, heads]".into(),
                ));
            }
            let name = text(&pair[0], "bookmark name")?.to_owned();
            let mut heads = array(&pair[1], "heads")?
                .iter()
                .map(|h| oref(h, "head"))
                .collect::<Result<Vec<_>, _>>()?;
            heads.sort();
            heads.dedup();
            view.bookmarks.insert(name, heads);
        }
        view.workspaces = workspaces_from_value(field(m, 1, "workspaces")?)?;
        Ok(view)
    }

    /// Format-1 encoding, kept for the migration test.
    #[cfg(test)]
    pub(crate) fn to_value(&self) -> Value {
        Value::map([
            (
                0,
                Value::Array(
                    self.bookmarks
                        .iter()
                        .map(|(n, hs)| {
                            Value::Array(vec![
                                Value::Text(n.clone()),
                                Value::Array(
                                    hs.iter().map(|h| Value::Bytes(h.0.to_vec())).collect(),
                                ),
                            ])
                        })
                        .collect(),
                ),
            ),
            (
                1,
                Value::Array(
                    self.workspaces
                        .iter()
                        .map(|(w, h)| {
                            Value::Array(vec![
                                Value::Bytes(w.0.to_vec()),
                                Value::Bytes(h.0.to_vec()),
                            ])
                        })
                        .collect(),
                ),
            ),
        ])
    }
}

/// A format-1 operation as read for migration.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Format1Op {
    pub parents: Vec<ObjectRef>,
    pub hlc: Hlc,
    pub command: String,
    pub view: Format1View,
}

impl Format1Op {
    #[cfg(test)]
    pub(crate) fn encode(&self) -> Vec<u8> {
        cbor::encode(&Value::map([
            (0, Value::Uint(FORMAT_VERSION)),
            (
                1,
                Value::Array(
                    self.parents
                        .iter()
                        .map(|p| Value::Bytes(p.0.to_vec()))
                        .collect(),
                ),
            ),
            (2, self.hlc.to_value()),
            (3, Value::Text(self.command.clone())),
            (4, self.view.to_value()),
        ]))
    }
}

/// Suffix on the `command` of operations recorded by an automatic
/// working-copy snapshot rather than by a user command.
pub const SNAPSHOT_SUFFIX: &str = " (snapshot)";

impl Op {
    /// Whether this operation only recorded a working-copy snapshot.
    pub fn is_snapshot(&self) -> bool {
        self.command.ends_with(SNAPSHOT_SUFFIX)
    }

    pub fn to_value(&self) -> Value {
        let mut fields = vec![
            (0, Value::Uint(FORMAT_VERSION)),
            (
                1,
                Value::Array(
                    self.parents
                        .iter()
                        .map(|p| Value::Bytes(p.0.to_vec()))
                        .collect(),
                ),
            ),
            (2, self.hlc.to_value()),
            (3, Value::Text(self.command.clone())),
            (4, self.view.to_value()),
        ];
        // Absent when unknown, so older operations keep their encoding.
        if let Some(w) = &self.workspace {
            fields.push((5, Value::Bytes(w.0.to_vec())));
        }
        if let Some(u) = &self.undoes {
            fields.push((6, Value::Bytes(u.0.to_vec())));
        }
        Value::map(fields)
    }
    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&self.to_value())
    }
    pub fn hash(&self) -> ObjectRef {
        hash_object(ObjectType::Op, &self.encode())
    }
    pub fn decode(b: &[u8]) -> Result<Op, ObjectError> {
        let v = cbor::decode(b)?;
        let m = v
            .as_map()
            .ok_or_else(|| ObjectError::Schema("op: expected map".into()))?;
        check_version(m)?;
        Ok(Op {
            parents: array(field(m, 1, "parents")?, "parents")?
                .iter()
                .map(|p| oref(p, "parent"))
                .collect::<Result<Vec<_>, _>>()?,
            hlc: Hlc::from_value(field(m, 2, "hlc")?)?,
            command: text(field(m, 3, "command")?, "command")?.to_owned(),
            view: View::from_value(field(m, 4, "view")?)?,
            workspace: match m.get(&5) {
                Some(v) => Some(
                    WorkspaceId::from_slice(bytes(v, "workspace")?).ok_or_else(|| {
                        ObjectError::Schema("workspace: expected 16 bytes".into())
                    })?,
                ),
                None => None,
            },
            undoes: m.get(&6).map(|v| oref(v, "undoes")).transpose()?,
        })
    }

    /// Read an operation written by repository format 1.
    pub fn decode_format1(b: &[u8]) -> Result<Format1Op, ObjectError> {
        let v = cbor::decode(b)?;
        let m = v
            .as_map()
            .ok_or_else(|| ObjectError::Schema("op: expected map".into()))?;
        check_version(m)?;
        Ok(Format1Op {
            parents: array(field(m, 1, "parents")?, "parents")?
                .iter()
                .map(|p| oref(p, "parent"))
                .collect::<Result<Vec<_>, _>>()?,
            hlc: Hlc::from_value(field(m, 2, "hlc")?)?,
            command: text(field(m, 3, "command")?, "command")?.to_owned(),
            view: Format1View::from_value(field(m, 4, "view")?)?,
        })
    }
}

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

    #[test]
    fn op_round_trip() {
        let mut view = View::default();
        view.bookmarks.insert("main".into(), ObjectRef([2; 32]));
        view.bookmarks.insert("dev".into(), ObjectRef([3; 32]));
        view.workspaces
            .insert(WorkspaceId([5; 16]), ObjectRef([9; 32]));
        view.remotes
            .entry("origin".into())
            .or_default()
            .insert("main".into(), ObjectRef([4; 32]));
        view.policy = Some(ObjectRef([6; 32]));
        view.tags.insert("v1".into(), ObjectRef([8; 32]));
        let op = Op {
            parents: vec![ObjectRef([7; 32])],
            hlc: Hlc {
                wall_ms: 5,
                logical: 1,
            },
            command: "oxy commit".into(),
            view,
            workspace: None,
            undoes: None,
        };
        let d = Op::decode(&op.encode()).unwrap();
        assert_eq!(d, op);
        // The workspace and an undo's target travel when known.
        let mut known = op.clone();
        known.workspace = Some(WorkspaceId([3; 16]));
        known.undoes = Some(ObjectRef([1; 32]));
        assert_eq!(Op::decode(&known.encode()).unwrap(), known);
        assert_ne!(known.hash(), op.hash());
        assert_eq!(d.hash(), Op::decode(&d.encode()).unwrap().hash());
        // A format-1 op does not decode as format 2, but does through the migration reader.
        let mut v1 = Format1View::default();
        v1.bookmarks
            .insert("main".into(), vec![ObjectRef([2; 32]), ObjectRef([1; 32])]);
        v1.workspaces
            .insert(WorkspaceId([5; 16]), ObjectRef([9; 32]));
        let old = Format1Op {
            parents: vec![],
            hlc: Hlc::default(),
            command: "oxy init".into(),
            view: v1,
        };
        assert!(Op::decode(&old.encode()).is_err());
        let back = Op::decode_format1(&old.encode()).unwrap();
        assert_eq!(
            back.view.bookmarks["main"],
            vec![ObjectRef([1; 32]), ObjectRef([2; 32])]
        );
    }
}