use std::ptr::NonNull;

use crate::bindings as ll_bindings;
use crate::metadata;
use crate::SizeType;
use crate::Time;
use crate::{tsk_id_t, TskitError};
use crate::{MutationId, NodeId, SiteId};
use ll_bindings::{tsk_mutation_table_free, tsk_mutation_table_init};

/// Row of a [`MutationTable`]
#[derive(Debug)]
pub struct MutationTableRow {
    pub id: MutationId,
    pub site: SiteId,
    pub node: NodeId,
    pub parent: MutationId,
    pub time: Time,
    pub derived_state: Option<Vec<u8>>,
    pub metadata: Option<Vec<u8>>,
}

impl PartialEq for MutationTableRow {
    fn eq(&self, other: &Self) -> bool {
        self.id == other.id
            && self.site == other.site
            && self.node == other.node
            && self.parent == other.parent
            && crate::util::partial_cmp_equal(&self.time, &other.time)
            && self.derived_state == other.derived_state
            && self.metadata == other.metadata
    }
}

fn make_mutation_table_row(table: &MutationTable, pos: tsk_id_t) -> Option<MutationTableRow> {
    let index = ll_bindings::tsk_size_t::try_from(pos).ok()?;
    match index {
        i if i < table.num_rows() => {
            let table_ref = table.as_ref();
            let derived_state = table.derived_state(pos).map(|s| s.to_vec());
            Some(MutationTableRow {
                id: pos.into(),
                site: table.site(pos)?,
                node: table.node(pos)?,
                parent: table.parent(pos)?,
                time: table.time(pos)?,
                derived_state,
                metadata: table_row_decode_metadata!(table, table_ref, pos).map(|m| m.to_vec()),
            })
        }
        _ => None,
    }
}

pub(crate) type MutationTableRefIterator<'a> =
    crate::table_iterator::TableIterator<&'a MutationTable>;
pub(crate) type MutationTableIterator = crate::table_iterator::TableIterator<MutationTable>;

impl<'a> Iterator for MutationTableRefIterator<'a> {
    type Item = MutationTableRow;

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

impl Iterator for MutationTableIterator {
    type Item = MutationTableRow;

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

/// An immutable view of site table.
///
/// These are not created directly but are accessed
/// by types implementing [`std::ops::Deref`] to
/// [`crate::table_views::TableViews`]
pub struct MutationTable {
    table_: NonNull<ll_bindings::tsk_mutation_table_t>,
}

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

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

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

    /// Return the ``site`` value from row ``row`` of the table.
    ///
    /// # Errors
    ///
    /// Will return [``IndexError``](crate::TskitError::IndexError)
    /// if ``row`` is out of range.
    pub fn site<M: Into<MutationId> + Copy>(&self, row: M) -> Option<SiteId> {
        unsafe_tsk_column_access!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            site,
            SiteId
        )
    }

    /// Return the ``node`` value from row ``row`` of the table.
    ///
    /// # Errors
    ///
    /// Will return [``IndexError``](crate::TskitError::IndexError)
    /// if ``row`` is out of range.
    pub fn node<M: Into<MutationId> + Copy>(&self, row: M) -> Option<NodeId> {
        unsafe_tsk_column_access!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            node,
            NodeId
        )
    }

    /// Return the ``parent`` value from row ``row`` of the table.
    ///
    /// # Errors
    ///
    /// Will return [``IndexError``](crate::TskitError::IndexError)
    /// if ``row`` is out of range.
    pub fn parent<M: Into<MutationId> + Copy>(&self, row: M) -> Option<MutationId> {
        unsafe_tsk_column_access!(
            row.into().0,
            0,
            self.num_rows(),
            self.as_ref(),
            parent,
            MutationId
        )
    }

    /// Return the ``time`` value from row ``row`` of the table.
    ///
    /// # Errors
    ///
    /// Will return [``IndexError``](crate::TskitError::IndexError)
    /// if ``row`` is out of range.
    pub fn time<M: Into<MutationId> + Copy>(&self, row: M) -> Option<Time> {
        unsafe_tsk_column_access!(row.into().0, 0, self.num_rows(), self.as_ref(), time, Time)
    }

    /// Get the ``derived_state`` value from row ``row`` of the table.
    ///
    /// # Return
    ///
    /// Will return `None` if there is no derived state.
    ///
    /// # Errors
    ///
    /// Will return [``IndexError``](crate::TskitError::IndexError)
    /// if ``row`` is out of range.
    pub fn derived_state<M: Into<MutationId>>(&self, row: M) -> Option<&[u8]> {
        metadata::char_column_to_slice(
            self,
            self.as_ref().derived_state,
            self.as_ref().derived_state_offset,
            row.into().0,
            self.as_ref().num_rows,
            self.as_ref().derived_state_length,
        )
    }

    /// 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::MutationMetadata>(
        &self,
        row: MutationId,
    ) -> 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 [`MutationTableRow`].
    pub fn iter(&self) -> impl Iterator<Item = MutationTableRow> + '_ {
        crate::table_iterator::make_table_iterator::<&MutationTable>(self)
    }

    /// Return row `r` of the table.
    ///
    /// # Parameters
    ///
    /// * `r`: the row id.
    ///
    /// # Returns
    ///
    /// * `Some(row)` if `r` is valid
    /// * `None` otherwise
    pub fn row<M: Into<MutationId> + Copy>(&self, r: M) -> Option<MutationTableRow> {
        let ri = r.into().0;
        table_row_access!(ri, self, make_mutation_table_row)
    }
}

build_owned_table_type!(
/// A standalone mutation table that owns its data.
///
/// # Examples
///
/// ```
/// use tskit::OwnedMutationTable;
///
/// let mut mutations = OwnedMutationTable::default();
/// let rowid = mutations.add_row(1, 2, 0, 1.0, None).unwrap();
/// assert_eq!(rowid, 0);
/// assert_eq!(mutations.num_rows(), 1);
/// ```
///
/// An example with metadata.
/// This requires the cargo feature `"derive"` for `tskit`.
///
/// ```
/// # #[cfg(any(feature="doc", feature="derive"))] {
/// use tskit::OwnedMutationTable;
///
/// #[derive(serde::Serialize,
///          serde::Deserialize,
///          tskit::metadata::MutationMetadata)]
/// #[serializer("serde_json")]
/// struct MutationMetadata {
///     value: i32,
/// }
///
/// let metadata = MutationMetadata{value: 42};
///
/// let mut mutations = OwnedMutationTable::default();
///
/// let rowid = mutations.add_row_with_metadata(0, 1, 5, 10.0, None, &metadata).unwrap();
/// assert_eq!(rowid, 0);
///
/// match mutations.metadata::<MutationMetadata>(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")
/// }
/// # }
/// ```
    => OwnedMutationTable,
    MutationTable,
    tsk_mutation_table_t,
    tsk_mutation_table_init,
    tsk_mutation_table_free,
    ll_bindings::tsk_mutation_table_clear
);

impl OwnedMutationTable {
    mutation_table_add_row!(=> add_row, self, *self.table);
    mutation_table_add_row_with_metadata!(=> add_row_with_metadata, self, *self.table);
}