//! Folder-sync bookkeeping: the folders this device mirrors, and the per-file
//! state each pass reconciles against.

use rusqlite::{OptionalExtension, params};

use super::Db;
use crate::Result;
use std::collections::HashMap;

pub struct StoredSyncFolder {
    pub id: i64,
    pub local_path: String,
    pub remote_uid: String,
    pub remote_share_id: String,
    /// `mirror` (full local copy, two-way synced) or `ondemand` (FUSE mount).
    pub mode: String,
    /// A mode the user asked for that could not be applied on the spot — the
    /// folder was mid-pass, or had un-uploaded changes. The engine applies it
    /// once the folder is safe to switch, so the request is queued rather than
    /// rejected. `None` when the folder is where the user wants it.
    pub pending_mode: Option<String>,
    /// `idle` | `syncing` | `error` | `conflict`.
    pub state: String,
    pub last_sync: i64,
}

/// One per-file sync baseline row: what a path looked like on both sides at the
/// last successful sync, so the next reconcile can tell which side changed.
/// `remote_rev`/`remote_hash` hold the remote signature —
/// its modification time and size as strings — since no cheap content hash is
/// exposed; change detection is `(mtime, size)` on each side.
#[derive(Clone, Debug, PartialEq)]
pub struct StoredSyncEntry {
    pub rel_path: String,
    pub remote_uid: Option<String>,
    pub local_mtime: i64,
    pub local_size: i64,
    /// The same modification time to nanosecond precision, when it is known.
    ///
    /// `local_mtime` alone cannot tell an edit that landed inside the same
    /// second as the last sync — and left the file the same length — from no
    /// edit at all, so those never uploaded (`docs/BUGS.md` B25). `None` on a row
    /// written before schema 28, which the comparison reads as "compare whole
    /// seconds", so upgrading does not make an entire mirror look changed.
    pub local_mtime_ns: Option<i64>,
    pub remote_rev: Option<String>,
    pub remote_hash: Option<String>,
    /// The id of the remote revision this row was synced at. A mirror upload
    /// checks it before it supersedes what Drive holds, because another client
    /// may have committed a revision since (`docs/BUGS.md` B249). `None` on a
    /// row written before schema 44, or by a pass that did not learn it; the
    /// check then falls back to `remote_rev` and `remote_hash`.
    pub remote_revision_id: Option<String>,
}

impl Db {
    pub fn sync_folder_add(
        &self,
        local_path: &str,
        remote_uid: &str,
        remote_share_id: &str,
    ) -> Result<i64> {
        let conn = self.conn.lock();
        conn.execute(
            "INSERT INTO sync_folder (local_path, remote_uid, remote_share_id)
             VALUES (?1, ?2, ?3)",
            params![local_path, remote_uid, remote_share_id],
        )?;
        Ok(conn.last_insert_rowid())
    }

    /// Every synced folder, oldest first.
    pub fn sync_folder_list(&self) -> Result<Vec<StoredSyncFolder>> {
        let conn = self.read();
        let mut stmt = conn.prepare(
            "SELECT id, local_path, remote_uid, remote_share_id, mode, pending_mode, state, last_sync
             FROM sync_folder ORDER BY id",
        )?;
        let rows = stmt.query_map([], |r| {
            Ok(StoredSyncFolder {
                id: r.get(0)?,
                local_path: r.get(1)?,
                remote_uid: r.get(2)?,
                remote_share_id: r.get(3)?,
                mode: r.get(4)?,
                pending_mode: r.get(5)?,
                state: r.get(6)?,
                last_sync: r.get(7)?,
            })
        })?;
        let mut items = Vec::new();
        for row in rows {
            items.push(row?);
        }
        Ok(items)
    }

    /// Look up one synced folder by id.
    pub fn sync_folder_get(&self, id: i64) -> Result<Option<StoredSyncFolder>> {
        let conn = self.read();
        conn.query_row(
            "SELECT id, local_path, remote_uid, remote_share_id, mode, pending_mode, state, last_sync
             FROM sync_folder WHERE id = ?1",
            params![id],
            |r| {
                Ok(StoredSyncFolder {
                    id: r.get(0)?,
                    local_path: r.get(1)?,
                    remote_uid: r.get(2)?,
                    remote_share_id: r.get(3)?,
                    mode: r.get(4)?,
                    pending_mode: r.get(5)?,
                    state: r.get(6)?,
                    last_sync: r.get(7)?,
                })
            },
        )
        .optional()
        .map_err(Into::into)
    }

    /// Remove a synced folder and its per-file baseline.
    pub fn sync_folder_remove(&self, id: i64) -> Result<bool> {
        let mut conn = self.conn.lock();
        let tx = conn.transaction()?;
        tx.execute("DELETE FROM sync_entry WHERE folder_id = ?1", params![id])?;
        let n = tx.execute("DELETE FROM sync_folder WHERE id = ?1", params![id])?;
        tx.commit()?;
        Ok(n > 0)
    }

    /// Update a synced folder's mode (`mirror`/`ondemand`). A queued request for
    /// that mode is satisfied and cleared in the same write. An opposite pending
    /// mode arrived after this transition started, so preserve it as the newer
    /// last-request intent.
    pub fn sync_folder_set_mode(&self, id: i64, mode: &str) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "UPDATE sync_folder
                SET mode = ?2,
                    pending_mode = CASE WHEN pending_mode = ?2 THEN NULL ELSE pending_mode END
              WHERE id = ?1",
            params![id, mode],
        )?;
        Ok(())
    }

    /// Re-point a synced folder at the share that now holds its remote folder,
    /// after the folder moved to another device without changing its uid.
    pub fn sync_folder_set_share(&self, id: i64, share_id: &str) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "UPDATE sync_folder SET remote_share_id = ?2 WHERE id = ?1",
            params![id, share_id],
        )?;
        Ok(())
    }

    /// Queue (or, with `None`, withdraw) a mode the folder should move to once it
    /// is safe to switch.
    pub fn sync_folder_set_pending_mode(&self, id: i64, mode: Option<&str>) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "UPDATE sync_folder SET pending_mode = ?2 WHERE id = ?1",
            params![id, mode],
        )?;
        Ok(())
    }

    /// Withdraw a queued mode only if it is still the intent the caller
    /// inspected. A newer request must survive an older settlement attempt.
    pub fn sync_folder_clear_pending_mode_if(&self, id: i64, expected: &str) -> Result<bool> {
        let conn = self.conn.lock();
        let changed = conn.execute(
            "UPDATE sync_folder SET pending_mode = NULL
             WHERE id = ?1 AND pending_mode = ?2",
            params![id, expected],
        )?;
        Ok(changed > 0)
    }

    /// Update a synced folder's state and stamp `last_sync` to now.
    pub fn sync_folder_set_state(&self, id: i64, state: &str, last_sync: i64) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "UPDATE sync_folder SET state = ?2, last_sync = ?3 WHERE id = ?1",
            params![id, state, last_sync],
        )?;
        Ok(())
    }

    /// The whole per-file sync baseline for a folder, keyed by relative path.
    pub fn sync_entries(&self, folder_id: i64) -> Result<HashMap<String, StoredSyncEntry>> {
        let conn = self.read();
        let mut stmt = conn.prepare(
            "SELECT rel_path, remote_uid, local_mtime, local_size, remote_rev, remote_hash,
                    local_mtime_ns, remote_revision_id
             FROM sync_entry WHERE folder_id = ?1",
        )?;
        let rows = stmt.query_map(params![folder_id], |r| {
            Ok(StoredSyncEntry {
                rel_path: r.get(0)?,
                remote_uid: r.get(1)?,
                local_mtime: r.get(2)?,
                local_size: r.get(3)?,
                remote_rev: r.get(4)?,
                remote_hash: r.get(5)?,
                local_mtime_ns: r.get(6)?,
                remote_revision_id: r.get(7)?,
            })
        })?;
        let mut map = HashMap::new();
        for row in rows {
            let e = row?;
            map.insert(e.rel_path.clone(), e);
        }
        Ok(map)
    }

    /// Whether `uid` is represented by a mirror location.
    ///
    /// An on-demand location proves residency through its live inode state.
    /// Mirror locations have no FUSE state, so their folder root comes from
    /// `sync_folder` and descendants come from the last successful
    /// `sync_entry` baseline.
    pub fn mirror_contains_uid(&self, uid: &str) -> Result<bool> {
        let conn = self.read();
        conn.query_row(
            "SELECT EXISTS(
                 SELECT 1
                   FROM sync_folder AS folder
              LEFT JOIN sync_entry AS entry ON entry.folder_id = folder.id
                  WHERE folder.mode = 'mirror'
                    AND (folder.remote_uid = ?1 OR entry.remote_uid = ?1)
             )",
            params![uid],
            |row| row.get(0),
        )
        .map_err(Into::into)
    }

    /// Insert or replace one baseline row.
    pub fn sync_entry_upsert(&self, folder_id: i64, e: &StoredSyncEntry) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "INSERT INTO sync_entry
               (folder_id, rel_path, remote_uid, local_mtime, local_size, remote_rev,
                remote_hash, local_mtime_ns, remote_revision_id)
             VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9)
             ON CONFLICT(folder_id, rel_path) DO UPDATE SET
               remote_uid         = excluded.remote_uid,
               local_mtime        = excluded.local_mtime,
               local_size         = excluded.local_size,
               remote_rev         = excluded.remote_rev,
               remote_hash        = excluded.remote_hash,
               local_mtime_ns     = excluded.local_mtime_ns,
               remote_revision_id = excluded.remote_revision_id",
            params![
                folder_id,
                e.rel_path,
                e.remote_uid,
                e.local_mtime,
                e.local_size,
                e.remote_rev,
                e.remote_hash,
                e.local_mtime_ns,
                e.remote_revision_id,
            ],
        )?;
        Ok(())
    }

    /// Drop one baseline row (a path that left the sync set on both sides).
    pub fn sync_entry_remove(&self, folder_id: i64, rel_path: &str) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "DELETE FROM sync_entry WHERE folder_id = ?1 AND rel_path = ?2",
            params![folder_id, rel_path],
        )?;
        Ok(())
    }

    /// Drop the baseline rows of `rel_path` and everything under it.
    ///
    /// Used when a subtree leaves a mirror folder through a move on Drive: its
    /// local copy is about to be removed, and rows left behind would read as
    /// "deleted locally" and trash the moved nodes at their new place.
    pub fn sync_entries_remove_subtree(&self, folder_id: i64, rel_path: &str) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "DELETE FROM sync_entry
              WHERE folder_id = ?1
                AND (rel_path = ?2 OR substr(rel_path, 1, length(?2) + 1) = ?2 || '/')",
            params![folder_id, rel_path],
        )?;
        Ok(())
    }

    /// Move the baseline rows of `from_rel` and everything under it to `to_rel`
    /// in folder `to_folder`, in one transaction.
    ///
    /// Used when a move on Drive took a mirror subtree along with its local
    /// copy: the rows still describe both sides correctly, only under a new
    /// path, so the next pass on either folder has nothing to do. The two
    /// folders may be the same one.
    pub fn sync_entries_move(
        &self,
        from_folder: i64,
        from_rel: &str,
        to_folder: i64,
        to_rel: &str,
    ) -> Result<()> {
        let mut conn = self.conn.lock();
        let tx = conn.transaction()?;
        {
            let mut select = tx.prepare(
                "SELECT rel_path, remote_uid, local_mtime, local_size, remote_rev, remote_hash,
                        local_mtime_ns, remote_revision_id
                   FROM sync_entry
                  WHERE folder_id = ?1
                    AND (rel_path = ?2 OR substr(rel_path, 1, length(?2) + 1) = ?2 || '/')",
            )?;
            let rows = select
                .query_map(params![from_folder, from_rel], |r| {
                    Ok(StoredSyncEntry {
                        rel_path: r.get(0)?,
                        remote_uid: r.get(1)?,
                        local_mtime: r.get(2)?,
                        local_size: r.get(3)?,
                        remote_rev: r.get(4)?,
                        remote_hash: r.get(5)?,
                        local_mtime_ns: r.get(6)?,
                        remote_revision_id: r.get(7)?,
                    })
                })?
                .collect::<rusqlite::Result<Vec<_>>>()?;
            let mut delete =
                tx.prepare("DELETE FROM sync_entry WHERE folder_id = ?1 AND rel_path = ?2")?;
            for row in &rows {
                delete.execute(params![from_folder, row.rel_path])?;
            }
            let mut insert = tx.prepare(
                "INSERT OR REPLACE INTO sync_entry
                   (folder_id, rel_path, remote_uid, local_mtime, local_size, remote_rev,
                    remote_hash, local_mtime_ns, remote_revision_id)
                 VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9)",
            )?;
            for row in rows {
                let rel = format!("{to_rel}{}", &row.rel_path[from_rel.len()..]);
                insert.execute(params![
                    to_folder,
                    rel,
                    row.remote_uid,
                    row.local_mtime,
                    row.local_size,
                    row.remote_rev,
                    row.remote_hash,
                    row.local_mtime_ns,
                    row.remote_revision_id,
                ])?;
            }
        }
        tx.commit()?;
        Ok(())
    }

    /// Drop the entire baseline for a folder. Used when flipping ondemand→mirror:
    /// the local tree was evicted, so the old baseline is stale and would make the
    /// next reconcile mistake "locally deleted" for "must re-download". Clearing it
    /// leaves an empty baseline + full remote = pure download.
    pub fn sync_entries_clear(&self, folder_id: i64) -> Result<()> {
        let conn = self.conn.lock();
        conn.execute(
            "DELETE FROM sync_entry WHERE folder_id = ?1",
            params![folder_id],
        )?;
        Ok(())
    }
}