use std::{iter::FromIterator, sync::Arc};

use crate::{
    array::{
        specification::{check_offsets_minimal, try_check_offsets_and_utf8},
        Array, MutableArray, Offset, TryExtend, TryPush,
    },
    bitmap::MutableBitmap,
    datatypes::DataType,
    error::{Error, Result},
    trusted_len::TrustedLen,
};

use super::Utf8Array;
use crate::array::physical_binary::*;
use crate::bitmap::Bitmap;

struct StrAsBytes<P>(P);
impl<T: AsRef<str>> AsRef<[u8]> for StrAsBytes<T> {
    #[inline]
    fn as_ref(&self) -> &[u8] {
        self.0.as_ref().as_bytes()
    }
}

/// The mutable version of [`Utf8Array`]. See [`MutableArray`] for more details.
#[derive(Debug)]
pub struct MutableUtf8Array<O: Offset> {
    data_type: DataType,
    offsets: Vec<O>,
    values: Vec<u8>,
    validity: Option<MutableBitmap>,
}

impl<O: Offset> From<MutableUtf8Array<O>> for Utf8Array<O> {
    fn from(other: MutableUtf8Array<O>) -> Self {
        // Safety:
        // `MutableUtf8Array` has the same invariants as `Utf8Array` and thus
        // `Utf8Array` can be safely created from `MutableUtf8Array` without checks.
        let validity = other.validity.and_then(|x| {
            let bitmap: Bitmap = x.into();
            if bitmap.unset_bits() == 0 {
                None
            } else {
                Some(bitmap)
            }
        });

        unsafe {
            Utf8Array::<O>::from_data_unchecked(
                other.data_type,
                other.offsets.into(),
                other.values.into(),
                validity,
            )
        }
    }
}

impl<O: Offset> Default for MutableUtf8Array<O> {
    fn default() -> Self {
        Self::new()
    }
}

impl<O: Offset> MutableUtf8Array<O> {
    /// Initializes a new empty [`MutableUtf8Array`].
    pub fn new() -> Self {
        Self {
            data_type: Self::default_data_type(),
            offsets: vec![O::default()],
            values: Vec::<u8>::new(),
            validity: None,
        }
    }

    /// Returns a [`MutableUtf8Array`] created from its internal representation.
    ///
    /// # Errors
    /// This function returns an error iff:
    /// * the offsets are not monotonically increasing
    /// * The last offset is not equal to the values' length.
    /// * the validity's length is not equal to `offsets.len() - 1`.
    /// * The `data_type`'s [`crate::datatypes::PhysicalType`] is not equal to either `Utf8` or `LargeUtf8`.
    /// * The `values` between two consecutive `offsets` are not valid utf8
    /// # Implementation
    /// This function is `O(N)` - checking monotinicity and utf8 is `O(N)`
    pub fn try_new(
        data_type: DataType,
        offsets: Vec<O>,
        values: Vec<u8>,
        validity: Option<MutableBitmap>,
    ) -> Result<Self> {
        try_check_offsets_and_utf8(&offsets, &values)?;
        if validity
            .as_ref()
            .map_or(false, |validity| validity.len() != offsets.len() - 1)
        {
            return Err(Error::oos(
                "validity's length must be equal to the number of values",
            ));
        }

        if data_type.to_physical_type() != Self::default_data_type().to_physical_type() {
            return Err(Error::oos(
                "MutableUtf8Array can only be initialized with DataType::Utf8 or DataType::LargeUtf8",
            ));
        }

        Ok(Self {
            data_type,
            offsets,
            values,
            validity,
        })
    }

    /// The canonical method to create a [`MutableUtf8Array`] out of low-end APIs.
    /// # Panics
    /// This function panics iff:
    /// * The `offsets` and `values` are inconsistent
    /// * The `values` between `offsets` are not utf8 encoded
    /// * The validity is not `None` and its length is different from `offsets`'s length minus one.
    pub fn from_data(
        data_type: DataType,
        offsets: Vec<O>,
        values: Vec<u8>,
        validity: Option<MutableBitmap>,
    ) -> Self {
        Self::try_new(data_type, offsets, values, validity).unwrap()
    }

    /// Create a [`MutableUtf8Array`] out of low-end APIs.
    /// # Safety
    /// The caller must ensure that every value between offsets is a valid utf8.
    /// # Panics
    /// This function panics iff:
    /// * The `offsets` and `values` are inconsistent
    /// * The validity is not `None` and its length is different from `offsets`'s length minus one.
    pub unsafe fn from_data_unchecked(
        data_type: DataType,
        offsets: Vec<O>,
        values: Vec<u8>,
        validity: Option<MutableBitmap>,
    ) -> Self {
        check_offsets_minimal(&offsets, values.len());
        if let Some(ref validity) = validity {
            assert_eq!(offsets.len() - 1, validity.len());
        }
        if data_type.to_physical_type() != Self::default_data_type().to_physical_type() {
            panic!("MutableUtf8Array can only be initialized with DataType::Utf8 or DataType::LargeUtf8")
        }
        Self {
            data_type,
            offsets,
            values,
            validity,
        }
    }

    fn default_data_type() -> DataType {
        Utf8Array::<O>::default_data_type()
    }

    /// Initializes a new [`MutableUtf8Array`] with a pre-allocated capacity of slots.
    pub fn with_capacity(capacity: usize) -> Self {
        Self::with_capacities(capacity, 0)
    }

    /// Initializes a new [`MutableUtf8Array`] with a pre-allocated capacity of slots and values.
    pub fn with_capacities(capacity: usize, values: usize) -> Self {
        let mut offsets = Vec::<O>::with_capacity(capacity + 1);
        offsets.push(O::default());

        Self {
            data_type: Self::default_data_type(),
            offsets,
            values: Vec::<u8>::with_capacity(values),
            validity: None,
        }
    }

    /// Reserves `additional` elements and `additional_values` on the values buffer.
    pub fn reserve(&mut self, additional: usize, additional_values: usize) {
        self.offsets.reserve(additional);
        if let Some(x) = self.validity.as_mut() {
            x.reserve(additional)
        }
        self.values.reserve(additional_values);
    }

    #[inline]
    fn last_offset(&self) -> O {
        *self.offsets.last().unwrap()
    }

    /// Pushes a new element to the array.
    /// # Panic
    /// This operation panics iff the length of all values (in bytes) exceeds `O` maximum value.
    #[inline]
    pub fn push<T: AsRef<str>>(&mut self, value: Option<T>) {
        self.try_push(value).unwrap()
    }

    /// Pop the last entry from [`MutableUtf8Array`].
    /// This function returns `None` iff this array is empty.
    pub fn pop(&mut self) -> Option<String> {
        if self.offsets.len() < 2 {
            return None;
        }
        self.offsets.pop()?;
        let value_start = self.offsets.iter().last().cloned()?.to_usize();
        let value = self.values.split_off(value_start);
        self.validity
            .as_mut()
            .map(|x| x.pop()?.then(|| ()))
            .unwrap_or_else(|| Some(()))
            .map(|_|
                // soundness: we always check for utf8 soundness on constructors.
                unsafe { String::from_utf8_unchecked(value) })
    }

    fn init_validity(&mut self) {
        let mut validity = MutableBitmap::with_capacity(self.offsets.capacity());
        validity.extend_constant(self.len(), true);
        validity.set(self.len() - 1, false);
        self.validity = Some(validity);
    }

    /// Converts itself into an [`Array`].
    pub fn into_arc(self) -> Arc<dyn Array> {
        let a: Utf8Array<O> = self.into();
        Arc::new(a)
    }

    /// Shrinks the capacity of the [`MutableUtf8Array`] to fit its current length.
    pub fn shrink_to_fit(&mut self) {
        self.values.shrink_to_fit();
        self.offsets.shrink_to_fit();
        if let Some(validity) = &mut self.validity {
            validity.shrink_to_fit()
        }
    }

    /// Extract the low-end APIs from the [`MutableUtf8Array`].
    pub fn into_data(self) -> (DataType, Vec<O>, Vec<u8>, Option<MutableBitmap>) {
        (self.data_type, self.offsets, self.values, self.validity)
    }
}

impl<O: Offset> MutableUtf8Array<O> {
    /// returns its values.
    pub fn values(&self) -> &Vec<u8> {
        &self.values
    }

    /// returns its offsets.
    pub fn offsets(&self) -> &Vec<O> {
        &self.offsets
    }
}

impl<O: Offset> MutableArray for MutableUtf8Array<O> {
    fn len(&self) -> usize {
        self.offsets.len() - 1
    }

    fn validity(&self) -> Option<&MutableBitmap> {
        self.validity.as_ref()
    }

    fn as_box(&mut self) -> Box<dyn Array> {
        // Safety:
        // `MutableUtf8Array` has the same invariants as `Utf8Array` and thus
        // `Utf8Array` can be safely created from `MutableUtf8Array` without checks.
        Box::new(unsafe {
            Utf8Array::from_data_unchecked(
                self.data_type.clone(),
                std::mem::take(&mut self.offsets).into(),
                std::mem::take(&mut self.values).into(),
                std::mem::take(&mut self.validity).map(|x| x.into()),
            )
        })
    }

    fn as_arc(&mut self) -> Arc<dyn Array> {
        // Safety:
        // `MutableUtf8Array` has the same invariants as `Utf8Array` and thus
        // `Utf8Array` can be safely created from `MutableUtf8Array` without checks.
        Arc::new(unsafe {
            Utf8Array::from_data_unchecked(
                self.data_type.clone(),
                std::mem::take(&mut self.offsets).into(),
                std::mem::take(&mut self.values).into(),
                std::mem::take(&mut self.validity).map(|x| x.into()),
            )
        })
    }

    fn data_type(&self) -> &DataType {
        if O::IS_LARGE {
            &DataType::LargeUtf8
        } else {
            &DataType::Utf8
        }
    }

    fn as_any(&self) -> &dyn std::any::Any {
        self
    }

    fn as_mut_any(&mut self) -> &mut dyn std::any::Any {
        self
    }

    #[inline]
    fn push_null(&mut self) {
        self.push::<&str>(None)
    }

    fn reserve(&mut self, additional: usize) {
        self.reserve(additional, 0)
    }

    fn shrink_to_fit(&mut self) {
        self.shrink_to_fit()
    }
}

impl<O: Offset, P: AsRef<str>> FromIterator<Option<P>> for MutableUtf8Array<O> {
    fn from_iter<I: IntoIterator<Item = Option<P>>>(iter: I) -> Self {
        Self::try_from_iter(iter).unwrap()
    }
}

impl<O: Offset> MutableUtf8Array<O> {
    /// Extends the [`MutableUtf8Array`] from an iterator of values of trusted len.
    /// This differs from `extended_trusted_len` which accepts iterator of optional values.
    #[inline]
    pub fn extend_trusted_len_values<I, P>(&mut self, iterator: I)
    where
        P: AsRef<str>,
        I: TrustedLen<Item = P>,
    {
        unsafe { self.extend_trusted_len_values_unchecked(iterator) }
    }

    /// Extends the [`MutableUtf8Array`] from an iterator of values.
    /// This differs from `extended_trusted_len` which accepts iterator of optional values.
    #[inline]
    pub fn extend_values<I, P>(&mut self, iterator: I)
    where
        P: AsRef<str>,
        I: Iterator<Item = P>,
    {
        let iterator = iterator.map(StrAsBytes);
        let additional = extend_from_values_iter(&mut self.offsets, &mut self.values, iterator);

        if let Some(validity) = self.validity.as_mut() {
            validity.extend_constant(additional, true);
        }
    }

    /// Extends the [`MutableUtf8Array`] from an iterator of values of trusted len.
    /// This differs from `extended_trusted_len_unchecked` which accepts iterator of optional
    /// values.
    /// # Safety
    /// The iterator must be trusted len.
    #[inline]
    pub unsafe fn extend_trusted_len_values_unchecked<I, P>(&mut self, iterator: I)
    where
        P: AsRef<str>,
        I: Iterator<Item = P>,
    {
        let (_, upper) = iterator.size_hint();
        let additional = upper.expect("extend_trusted_len_values requires an upper limit");

        let iterator = iterator.map(StrAsBytes);
        extend_from_trusted_len_values_iter(&mut self.offsets, &mut self.values, iterator);

        if let Some(validity) = self.validity.as_mut() {
            validity.extend_constant(additional, true);
        }
    }

    /// Extends the [`MutableUtf8Array`] from an iterator of trusted len.
    #[inline]
    pub fn extend_trusted_len<I, P>(&mut self, iterator: I)
    where
        P: AsRef<str>,
        I: TrustedLen<Item = Option<P>>,
    {
        unsafe { self.extend_trusted_len_unchecked(iterator) }
    }

    /// Extends [`MutableUtf8Array`] from an iterator of trusted len.
    /// # Safety
    /// The iterator must be trusted len.
    #[inline]
    pub unsafe fn extend_trusted_len_unchecked<I, P>(&mut self, iterator: I)
    where
        P: AsRef<str>,
        I: Iterator<Item = Option<P>>,
    {
        if self.validity.is_none() {
            let mut validity = MutableBitmap::new();
            validity.extend_constant(self.len(), true);
            self.validity = Some(validity);
        }

        let iterator = iterator.map(|x| x.map(StrAsBytes));
        extend_from_trusted_len_iter(
            &mut self.offsets,
            &mut self.values,
            self.validity.as_mut().unwrap(),
            iterator,
        );
    }

    /// Creates a [`MutableUtf8Array`] from an iterator of trusted length.
    /// # Safety
    /// The iterator must be [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html).
    /// I.e. that `size_hint().1` correctly reports its length.
    #[inline]
    pub unsafe fn from_trusted_len_iter_unchecked<I, P>(iterator: I) -> Self
    where
        P: AsRef<str>,
        I: Iterator<Item = Option<P>>,
    {
        let iterator = iterator.map(|x| x.map(StrAsBytes));
        let (validity, offsets, values) = trusted_len_unzip(iterator);

        // soundness: P is `str`
        Self::from_data_unchecked(Self::default_data_type(), offsets, values, validity)
    }

    /// Creates a [`MutableUtf8Array`] from an iterator of trusted length.
    #[inline]
    pub fn from_trusted_len_iter<I, P>(iterator: I) -> Self
    where
        P: AsRef<str>,
        I: TrustedLen<Item = Option<P>>,
    {
        // soundness: I is `TrustedLen`
        unsafe { Self::from_trusted_len_iter_unchecked(iterator) }
    }

    /// Creates a [`MutableUtf8Array`] from an iterator of trusted length of `&str`.
    /// # Safety
    /// The iterator must be [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html).
    /// I.e. that `size_hint().1` correctly reports its length.
    #[inline]
    pub unsafe fn from_trusted_len_values_iter_unchecked<T: AsRef<str>, I: Iterator<Item = T>>(
        iterator: I,
    ) -> Self {
        let iterator = iterator.map(StrAsBytes);
        let (offsets, values) = unsafe { trusted_len_values_iter(iterator) };
        // soundness: T is AsRef<str>
        Self::from_data_unchecked(Self::default_data_type(), offsets, values, None)
    }

    /// Creates a new [`MutableUtf8Array`] from a [`TrustedLen`] of `&str`.
    #[inline]
    pub fn from_trusted_len_values_iter<T: AsRef<str>, I: TrustedLen<Item = T>>(
        iterator: I,
    ) -> Self {
        // soundness: I is `TrustedLen`
        unsafe { Self::from_trusted_len_values_iter_unchecked(iterator) }
    }

    /// Creates a new [`MutableUtf8Array`] from an iterator.
    /// # Error
    /// This operation errors iff the total length in bytes on the iterator exceeds `O`'s maximum value.
    /// (`i32::MAX` or `i64::MAX` respectively).
    fn try_from_iter<P: AsRef<str>, I: IntoIterator<Item = Option<P>>>(iter: I) -> Result<Self> {
        let iterator = iter.into_iter();
        let (lower, _) = iterator.size_hint();
        let mut array = Self::with_capacity(lower);
        for item in iterator {
            array.try_push(item)?;
        }
        Ok(array)
    }

    /// Creates a [`MutableUtf8Array`] from an falible iterator of trusted length.
    /// # Safety
    /// The iterator must be [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html).
    /// I.e. that `size_hint().1` correctly reports its length.
    #[inline]
    pub unsafe fn try_from_trusted_len_iter_unchecked<E, I, P>(
        iterator: I,
    ) -> std::result::Result<Self, E>
    where
        P: AsRef<str>,
        I: IntoIterator<Item = std::result::Result<Option<P>, E>>,
    {
        let iterator = iterator.into_iter();

        let iterator = iterator.map(|x| x.map(|x| x.map(StrAsBytes)));
        let (validity, offsets, values) = try_trusted_len_unzip(iterator)?;

        // soundness: P is `str`
        Ok(Self::from_data_unchecked(
            Self::default_data_type(),
            offsets,
            values,
            validity,
        ))
    }

    /// Creates a [`MutableUtf8Array`] from an falible iterator of trusted length.
    #[inline]
    pub fn try_from_trusted_len_iter<E, I, P>(iterator: I) -> std::result::Result<Self, E>
    where
        P: AsRef<str>,
        I: TrustedLen<Item = std::result::Result<Option<P>, E>>,
    {
        // soundness: I: TrustedLen
        unsafe { Self::try_from_trusted_len_iter_unchecked(iterator) }
    }

    /// Creates a new [`MutableUtf8Array`] from a [`Iterator`] of `&str`.
    pub fn from_iter_values<T: AsRef<str>, I: Iterator<Item = T>>(iterator: I) -> Self {
        let iterator = iterator.map(StrAsBytes);
        let (offsets, values) = values_iter(iterator);
        // soundness: T: AsRef<str>
        unsafe { Self::from_data_unchecked(Self::default_data_type(), offsets, values, None) }
    }
}

impl<O: Offset, T: AsRef<str>> Extend<Option<T>> for MutableUtf8Array<O> {
    fn extend<I: IntoIterator<Item = Option<T>>>(&mut self, iter: I) {
        self.try_extend(iter).unwrap();
    }
}

impl<O: Offset, T: AsRef<str>> TryExtend<Option<T>> for MutableUtf8Array<O> {
    fn try_extend<I: IntoIterator<Item = Option<T>>>(&mut self, iter: I) -> Result<()> {
        let mut iter = iter.into_iter();
        self.reserve(iter.size_hint().0, 0);
        iter.try_for_each(|x| self.try_push(x))
    }
}

impl<O: Offset, T: AsRef<str>> TryPush<Option<T>> for MutableUtf8Array<O> {
    #[inline]
    fn try_push(&mut self, value: Option<T>) -> Result<()> {
        match value {
            Some(value) => {
                let bytes = value.as_ref().as_bytes();
                self.values.extend_from_slice(bytes);

                let size = O::from_usize(self.values.len()).ok_or(Error::Overflow)?;

                self.offsets.push(size);

                match &mut self.validity {
                    Some(validity) => validity.push(true),
                    None => {}
                }
            }
            None => {
                self.offsets.push(self.last_offset());
                match &mut self.validity {
                    Some(validity) => validity.push(false),
                    None => self.init_validity(),
                }
            }
        }
        Ok(())
    }
}