use std::{collections::HashSet, str::FromStr};

use futures::Sink;
use tokio::io::AsyncWrite;

use crate::{
    element::{Element, Name, NamespaceDeclaration},
    error::Error,
    xml::{self, composers::Composer, parsers_complete::Parser, ETag},
    Result,
};

// pub struct Writer<W, C = Composer> {
pub struct Writer<W> {
    inner: W,
    depth: Vec<Name>,
    namespace_declarations: Vec<HashSet<NamespaceDeclaration>>,
}

impl<W: AsyncWrite + Unpin> Writer<W> {
    pub async fn write(&mut self, element: Element) -> Result<()> {
        todo!()
    }

    pub async fn write_start(&mut self, element: Element) -> Result<()> {
        let mut namespace_declarations_stack: Vec<_> = self
            .namespace_declarations
            .iter()
            .flatten()
            .chain(&element.namespace_declarations)
            .collect();
        let name_namespace_declaration = namespace_declarations_stack
            .iter()
            .rfind(|namespace_declaration| {
                namespace_declaration.namespace == element.name.namespace
            })
            .ok_or(Error::UndeclaredNamespace(element.name.namespace.clone()))?;
        let prefix = &name_namespace_declaration.prefix;
        let name;
        if let Some(prefix) = &prefix {
            name = xml::QName::PrefixedName(xml::PrefixedName {
                prefix: xml::Prefix::parse_full(prefix)?,
                local_part: xml::LocalPart::parse_full(&element.name.local_name)?,
            })
        } else {
            name = xml::QName::UnprefixedName(xml::UnprefixedName::parse_full(
                &element.name.local_name,
            )?)
        }

        namespace_declarations_stack.push(name_namespace_declaration);

        let mut attributes = Vec::new();

        for namespace_declaration in &element.namespace_declarations {
            let ns_name = namespace_declaration
                .prefix
                .as_ref()
                .map(|prefix| -> Result<_> {
                    Ok(xml::NSAttName::PrefixedAttName(
                        xml::PrefixedAttName::parse_full(&prefix)?,
                    ))
                })
                .unwrap_or(Ok(xml::NSAttName::DefaultAttName))?;
            let value = xml::AttValue::from(namespace_declaration.namespace.as_str());
            let xml_attribute = xml::Attribute::NamespaceDeclaration { ns_name, value };
            attributes.push(xml_attribute);
        }

        let s_tag = xml::STag { name, attributes };

        s_tag.write(&mut self.inner).await?;

        self.depth.push(element.name);
        self.namespace_declarations
            .push(element.namespace_declarations);
        Ok(())
    }

    pub async fn write_end(&mut self) -> Result<()> {
        if let Some(name) = &self.depth.pop() {
            let e_tag;
            let namespace_declarations_stack: Vec<_> =
                self.namespace_declarations.iter().flatten().collect();
            let namespace_declaration = namespace_declarations_stack
                .iter()
                .rfind(|namespace_declaration| namespace_declaration.namespace == name.namespace)
                // will always be in this vector
                .unwrap();
            let prefix = &namespace_declaration.prefix;
            if let Some(prefix) = &prefix {
                e_tag = xml::ETag {
                    name: xml::QName::PrefixedName(xml::PrefixedName {
                        prefix: xml::Prefix::parse_full(prefix)?,
                        local_part: xml::LocalPart::parse_full(&name.local_name)?,
                    }),
                };
            } else {
                e_tag = xml::ETag {
                    name: xml::QName::UnprefixedName(xml::UnprefixedName::parse_full(
                        &name.local_name,
                    )?),
                };
            }
            e_tag.write(&mut self.inner).await?;
            self.namespace_declarations.pop();
            Ok(())
        } else {
            return Err(Error::NotInElement("".to_string()));
        }
    }
}

impl<W: AsyncWrite, E: Into<Element>> Sink<E> for Writer<W> {
    type Error = Error;

    fn poll_ready(
        self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Result<()>> {
        todo!()
    }

    fn start_send(self: std::pin::Pin<&mut Self>, item: E) -> Result<()> {
        todo!()
    }

    fn poll_flush(
        self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Result<()>> {
        todo!()
    }

    fn poll_close(
        self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Result<()>> {
        todo!()
    }
}