use std::ptr::NonNull;

use crate::bindings as ll_bindings;
use crate::metadata;
use crate::Position;
use crate::{tsk_id_t, TskitError};
use crate::{EdgeId, NodeId};
use ll_bindings::{tsk_edge_table_free, tsk_edge_table_init};

/// Row of an [`EdgeTable`]
#[derive(Debug)]
pub struct EdgeTableRow {
    pub id: EdgeId,
    pub left: Position,
    pub right: Position,
    pub parent: NodeId,
    pub child: NodeId,
    pub metadata: Option<Vec<u8>>,
}

impl PartialEq for EdgeTableRow {
    fn eq(&self, other: &Self) -> bool {
        self.id == other.id
            && self.parent == other.parent
            && self.child == other.child
            && crate::util::partial_cmp_equal(&self.left, &other.left)
            && crate::util::partial_cmp_equal(&self.right, &other.right)
            && self.metadata == other.metadata
    }
}

fn make_edge_table_row(table: &EdgeTable, pos: tsk_id_t) -> Option<EdgeTableRow> {
    let table_ref = table.as_ref();
    Some(EdgeTableRow {
        id: pos.into(),
        left: table.left(pos)?,
        right: table.right(pos)?,
        parent: table.parent(pos)?,
        child: table.child(pos)?,
        metadata: table_row_decode_metadata!(table, table_ref, pos).map(|m| m.to_vec()),
    })
}

pub(crate) type EdgeTableRefIterator<'a> = crate::table_iterator::TableIterator<&'a EdgeTable>;
pub(crate) type EdgeTableIterator = crate::table_iterator::TableIterator<EdgeTable>;

impl<'a> Iterator for EdgeTableRefIterator<'a> {
    type Item = EdgeTableRow;

    fn next(&mut self) -> Option<Self::Item> {
        let rv = make_edge_table_row(self.table, self.pos);
        self.pos += 1;
        rv
    }
}

impl Iterator for EdgeTableIterator {
    type Item = EdgeTableRow;

    fn next(&mut self) -> Option<Self::Item> {
        let rv = make_edge_table_row(&self.table, self.pos);
        self.pos += 1;
        rv
    }
}

/// An immutable view of an edge table.
///
/// These are not created directly but are accessed
/// by types implementing [`std::ops::Deref`] to
/// [`crate::table_views::TableViews`]
#[repr(transparent)]
pub struct EdgeTable {
    pub(crate) table_: NonNull<ll_bindings::tsk_edge_table_t>,
}

impl EdgeTable {
    pub(crate) fn new_from_table(
        edges: *mut ll_bindings::tsk_edge_table_t,
    ) -> Result<Self, TskitError> {
        let n = NonNull::new(edges).ok_or_else(|| {
            TskitError::LibraryError("null pointer to tsk_edge_table_t".to_string())
        })?;
        Ok(EdgeTable { table_: n })
    }

    pub(crate) fn as_ref(&self) -> &ll_bindings::tsk_edge_table_t {
        // SAFETY: NonNull
        unsafe { self.table_.as_ref() }
    }

    /// Return the number of rows
    pub fn num_rows(&self) -> crate::SizeType {
        self.as_ref().num_rows.into()
    }

    /// Return the ``parent`` value from row ``row`` of the table.
    ///
    /// # Returns
    ///
    /// * `Some(parent)` if `u` is valid.
    /// * `None` otherwise.
    pub fn parent<E: Into<EdgeId> + Copy>(&self, row: E) -> Option<NodeId> {
        unsafe_tsk_column_access!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            parent,
            NodeId
        )
    }

    /// Return the ``child`` value from row ``row`` of the table.
    ///
    /// # Returns
    ///
    /// * `Some(child)` if `u` is valid.
    /// * `None` otherwise.
    pub fn child<E: Into<EdgeId> + Copy>(&self, row: E) -> Option<NodeId> {
        unsafe_tsk_column_access!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            child,
            NodeId
        )
    }

    /// Return the ``left`` value from row ``row`` of the table.
    ///
    /// # Returns
    ///
    /// * `Some(position)` if `u` is valid.
    /// * `None` otherwise.
    pub fn left<E: Into<EdgeId> + Copy>(&self, row: E) -> Option<Position> {
        unsafe_tsk_column_access!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            left,
            Position
        )
    }

    /// Return the ``right`` value from row ``row`` of the table.
    ///
    /// # Returns
    ///
    /// * `Some(position)` if `u` is valid.
    /// * `None` otherwise.
    pub fn right<E: Into<EdgeId> + Copy>(&self, row: E) -> Option<Position> {
        unsafe_tsk_column_access_and_map_into!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            right
        )
    }

    /// Retrieve decoded metadata for a `row`.
    ///
    /// # Returns
    ///
    /// * `Some(Ok(T))` if `row` is valid and decoding succeeded.
    /// * `Some(Err(_))` if `row` is not valid and decoding failed.
    /// * `None` if `row` is not valid.
    ///
    /// # Errors
    ///
    /// * [`TskitError::MetadataError`] if decoding fails.
    ///
    /// # Examples.
    ///
    /// The big-picture semantics are the same for all table types.
    /// See [`crate::IndividualTable::metadata`] for examples.
    pub fn metadata<T: metadata::EdgeMetadata>(
        &self,
        row: EdgeId,
    ) -> Option<Result<T, TskitError>> {
        let table_ref = self.as_ref();
        let buffer = metadata_to_vector!(self, table_ref, row.0)?;
        Some(decode_metadata_row!(T, buffer).map_err(|e| e.into()))
    }

    /// Return an iterator over rows of the table.
    /// The value of the iterator is [`EdgeTableRow`].
    ///
    pub fn iter(&self) -> impl Iterator<Item = EdgeTableRow> + '_ {
        crate::table_iterator::make_table_iterator::<&EdgeTable>(self)
    }

    /// Return row `r` of the table.
    ///
    /// # Parameters
    ///
    /// * `r`: the row id.
    ///
    /// # Returns
    ///
    /// * `Some(row)` if `r` is valid
    /// * `None` otherwise
    pub fn row<E: Into<EdgeId> + Copy>(&self, r: E) -> Option<EdgeTableRow> {
        table_row_access!(r.into().0, self, make_edge_table_row)
    }
}

build_owned_table_type!(
    /// A standalone edge table that owns its data.
    ///
    /// # Examples
    ///
    /// ```
    /// use tskit::OwnedEdgeTable;
    ///
    /// let mut edges = OwnedEdgeTable::default();
    /// let rowid = edges.add_row(1., 2., 0, 1).unwrap();
    /// assert_eq!(rowid, 0);
    /// assert_eq!(edges.num_rows(), 1);
    ///
    /// edges.clear().unwrap();
    /// assert_eq!(edges.num_rows(), 0);
    /// ```
    ///
    /// An example with metadata.
    /// This requires the cargo feature `"derive"` for `tskit`.
    ///
    /// ```
    /// # #[cfg(any(feature="doc", feature="derive"))] {
    /// use tskit::OwnedEdgeTable;
    ///
    /// #[derive(serde::Serialize,
    ///          serde::Deserialize,
    ///          tskit::metadata::EdgeMetadata)]
    /// #[serializer("serde_json")]
    /// struct EdgeMetadata {
    ///     value: i32,
    /// }
    ///
    /// let metadata = EdgeMetadata{value: 42};
    ///
    /// let mut edges = OwnedEdgeTable::default();
    ///
    /// let rowid = edges.add_row_with_metadata(0., 1., 5, 10, &metadata).unwrap();
    /// assert_eq!(rowid, 0);
    ///
    /// match edges.metadata::<EdgeMetadata>(rowid) {
    ///     // rowid is in range, decoding succeeded
    ///     Some(Ok(decoded)) => assert_eq!(decoded.value, 42),
    ///     // rowid is in range, decoding failed
    ///     Some(Err(e)) => panic!("error decoding metadata: {:?}", e),
    ///     None => panic!("row id out of range")
    /// }
    /// # }
    /// ```
    => OwnedEdgeTable,
    EdgeTable,
    tsk_edge_table_t,
    tsk_edge_table_init,
    tsk_edge_table_free,
    crate::bindings::tsk_edge_table_clear
);

impl OwnedEdgeTable {
    edge_table_add_row!(=> add_row, self, *self.table);
    edge_table_add_row_with_metadata!(=> add_row_with_metadata, self, *self.table);
}