use std::collections::BTreeSet;
use std::fmt::Debug;
use std::str::FromStr;

use super::diff::artificial_diff_scope;
use super::diff::compare_ast_node;
use super::diff::DiffEntry;
use super::diff::DiffStatus;
use super::sexp::unquote;
use super::sexp::Token;
use super::util::get_property;
use super::util::get_property_numeric;
use super::util::get_property_quoted_string;
use super::util::get_property_unquoted_atom;
use crate::types::AstNode;

#[derive(Debug)]
pub(crate) enum EmacsField<'s> {
    Required(&'s str),
    Optional(&'s str),
}

#[derive(Debug)]
pub(crate) enum ComparePropertiesResult<'b, 's> {
    NoChange,
    /// Return when you want the status for "this" node to change (as opposed to collecting child status).
    SelfChange(DiffStatus, Option<String>),
    DiffEntry(DiffEntry<'b, 's>),
}

/// Do no comparison.
///
/// This is for when you want to acknowledge that a field exists in the emacs token, but you do not have any validation for it when using the compare_properties!() macro. Ideally, this should be kept to a minimum since this represents untested values.
pub(crate) fn compare_noop<'b, 's, 'x, R, RG>(
    _source: &'s str,
    _emacs: &'b Token<'s>,
    _rust_node: R,
    _emacs_field: &'x str,
    _rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    Ok(ComparePropertiesResult::NoChange)
}

/// Do no comparison.
///
/// This is for when you want to acknowledge that a field exists in the emacs token, but you do not have any validation for it when using the compare_properties!() macro. Ideally, this should be kept to a minimum since this represents untested values.
pub(crate) fn compare_identity() -> () {
    ()
}

/// Assert that the emacs value is always nil or absent.
///
/// This is usually used for fields which, in my testing, are always nil. Using this compare function instead of simply doing a compare_noop will enable us to be alerted when we finally come across an org-mode document that has a value other than nil for the property.
pub(crate) fn compare_property_always_nil<'b, 's, 'x, R, RG>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    _rust_node: R,
    emacs_field: &'x str,
    _rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    let value = get_property(emacs, emacs_field)?;
    if value.is_some() {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} was expected to always be nil: {:?}",
            emacs_field, value
        ));
        Ok(ComparePropertiesResult::SelfChange(this_status, message))
    } else {
        Ok(ComparePropertiesResult::NoChange)
    }
}

pub(crate) fn compare_property_quoted_string<
    'b,
    's,
    'x,
    R,
    RV: AsRef<str> + std::fmt::Debug,
    RG: Fn(R) -> Option<RV>,
>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    let value = get_property_quoted_string(emacs, emacs_field)?;
    let rust_value = rust_value_getter(rust_node);
    if rust_value.as_ref().map(|s| s.as_ref()) != value.as_ref().map(String::as_str) {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch (emacs != rust) {:?} != {:?}",
            emacs_field, value, rust_value
        ));
        Ok(ComparePropertiesResult::SelfChange(this_status, message))
    } else {
        Ok(ComparePropertiesResult::NoChange)
    }
}

pub(crate) fn compare_property_unquoted_atom<'b, 's, 'x, R, RG: Fn(R) -> Option<&'s str>>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    let value = get_property_unquoted_atom(emacs, emacs_field)?;
    let rust_value = rust_value_getter(rust_node);
    if rust_value != value {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch (emacs != rust) {:?} != {:?}",
            emacs_field, value, rust_value
        ));
        Ok(ComparePropertiesResult::SelfChange(this_status, message))
    } else {
        Ok(ComparePropertiesResult::NoChange)
    }
}

pub(crate) fn compare_property_numeric<
    'b,
    's,
    'x,
    R,
    RV: FromStr + PartialEq + Debug,
    RG: Fn(R) -> Option<RV>,
>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error + 's>>
where
    <RV as FromStr>::Err: std::error::Error,
    <RV as FromStr>::Err: 's,
{
    let value = get_property_numeric::<RV>(emacs, emacs_field)?;
    let rust_value = rust_value_getter(rust_node);
    if rust_value != value {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch (emacs != rust) {:?} != {:?}",
            emacs_field, value, rust_value
        ));
        Ok(ComparePropertiesResult::SelfChange(this_status, message))
    } else {
        Ok(ComparePropertiesResult::NoChange)
    }
}

pub(crate) fn compare_property_list_of_quoted_string<
    'b,
    's,
    'x,
    R,
    RV: AsRef<str> + std::fmt::Debug,
    RI: Iterator<Item = RV>,
    RG: Fn(R) -> Option<RI>,
>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    let value = get_property(emacs, emacs_field)?
        .map(Token::as_list)
        .map_or(Ok(None), |r| r.map(Some))?;
    let rust_value = rust_value_getter(rust_node);
    // TODO: Seems we are needlessly coverting to a vec here.
    let rust_value: Option<Vec<RV>> = rust_value.map(|it| it.collect());
    match (value, &rust_value) {
        (None, None) => {}
        (None, Some(_)) | (Some(_), None) => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, value, rust_value
            ));
            return Ok(ComparePropertiesResult::SelfChange(this_status, message));
        }
        (Some(el), Some(rl)) if el.len() != rl.len() => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, value, rust_value
            ));
            return Ok(ComparePropertiesResult::SelfChange(this_status, message));
        }
        (Some(el), Some(rl)) => {
            for (e, r) in el.iter().zip(rl) {
                let e = unquote(e.as_atom()?)?;
                let r = r.as_ref();
                if e != r {
                    let this_status = DiffStatus::Bad;
                    let message = Some(format!(
                        "{} mismatch (emacs != rust) {:?} != {:?}. Full list: {:?} != {:?}",
                        emacs_field, e, r, value, rust_value
                    ));
                    return Ok(ComparePropertiesResult::SelfChange(this_status, message));
                }
            }
        }
    }
    Ok(ComparePropertiesResult::NoChange)
}

pub(crate) fn compare_property_set_of_quoted_string<
    'a,
    'b,
    's,
    'x,
    R,
    RV: AsRef<str> + std::fmt::Debug + Ord + 'a + ?Sized,
    RI: Iterator<Item = &'a RV>,
    RG: Fn(R) -> Option<RI>,
>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    let value = get_property(emacs, emacs_field)?
        .map(Token::as_list)
        .map_or(Ok(None), |r| r.map(Some))?;
    let empty = Vec::new();
    let value = value.unwrap_or(&empty);
    let rust_value = rust_value_getter(rust_node);
    let rust_value = if let Some(rust_value) = rust_value {
        let slices: BTreeSet<&str> = rust_value.map(|rv| rv.as_ref()).collect();
        slices
    } else {
        BTreeSet::new()
    };
    let value: Vec<&str> = value
        .iter()
        .map(|e| e.as_atom())
        .collect::<Result<Vec<_>, _>>()?;
    let value: Vec<String> = value
        .into_iter()
        .map(unquote)
        .collect::<Result<Vec<_>, _>>()?;
    let value: BTreeSet<&str> = value.iter().map(|e| e.as_str()).collect();
    let mismatched: Vec<_> = value
        .symmetric_difference(&rust_value)
        .map(|val| *val)
        .collect();
    if !mismatched.is_empty() {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch. Mismatched values: {}",
            emacs_field,
            mismatched.join(", ")
        ));
        return Ok(ComparePropertiesResult::SelfChange(this_status, message));
    }
    Ok(ComparePropertiesResult::NoChange)
}

pub(crate) fn compare_property_boolean<'b, 's, 'x, R, RG: Fn(R) -> bool>(
    _source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>> {
    // get_property already converts nil to None.
    let value = get_property(emacs, emacs_field)?.is_some();
    let rust_value = rust_value_getter(rust_node);
    if rust_value != value {
        let this_status = DiffStatus::Bad;
        let message = Some(format!(
            "{} mismatch (emacs != rust) {:?} != {:?}",
            emacs_field, value, rust_value
        ));
        Ok(ComparePropertiesResult::SelfChange(this_status, message))
    } else {
        Ok(ComparePropertiesResult::NoChange)
    }
}

pub(crate) fn compare_property_single_ast_node<
    'b,
    's,
    'x: 'b + 's,
    R,
    RV: std::fmt::Debug,
    RG: Fn(R) -> Option<RV>,
>(
    source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>>
where
    AstNode<'b, 's>: From<RV>,
{
    let value = get_property(emacs, emacs_field)?;
    let rust_value = rust_value_getter(rust_node);
    match (value, rust_value) {
        (None, None) => {}
        (None, rv @ Some(_)) | (Some(_), rv @ None) => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, value, rv
            ));
            return Ok(ComparePropertiesResult::SelfChange(this_status, message));
        }
        (Some(ev), Some(rv)) => {
            let child_status: Vec<DiffEntry<'b, 's>> =
                vec![compare_ast_node(source, ev, rv.into())?];
            let diff_scope = artificial_diff_scope(emacs_field, child_status)?;
            return Ok(ComparePropertiesResult::DiffEntry(diff_scope));
        }
    }
    Ok(ComparePropertiesResult::NoChange)
}

pub(crate) fn compare_property_list_of_ast_nodes<
    'b,
    's,
    'x: 'b + 's,
    R,
    RV: std::fmt::Debug,
    RI: Iterator<Item = RV>,
    RG: Fn(R) -> Option<RI>,
>(
    source: &'s str,
    emacs: &'b Token<'s>,
    rust_node: R,
    emacs_field: &'x str,
    rust_value_getter: RG,
) -> Result<ComparePropertiesResult<'b, 's>, Box<dyn std::error::Error>>
where
    AstNode<'b, 's>: From<RV>,
{
    let value = get_property(emacs, emacs_field)?
        .map(Token::as_list)
        .map_or(Ok(None), |r| r.map(Some))?;
    let rust_value = rust_value_getter(rust_node);
    // TODO: Seems we are needlessly coverting to a vec here.
    let rust_value: Option<Vec<RV>> = rust_value.map(|it| it.collect());
    match (value, rust_value) {
        (None, None) => {}
        (None, rv @ Some(_)) | (Some(_), rv @ None) => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, value, rv
            ));
            return Ok(ComparePropertiesResult::SelfChange(this_status, message));
        }
        (Some(el), Some(rl)) if el.len() != rl.len() => {
            let this_status = DiffStatus::Bad;
            let message = Some(format!(
                "{} mismatch (emacs != rust) {:?} != {:?}",
                emacs_field, el, rl
            ));
            return Ok(ComparePropertiesResult::SelfChange(this_status, message));
        }
        (Some(el), Some(rl)) => {
            let mut child_status: Vec<DiffEntry<'b, 's>> = Vec::with_capacity(rl.len());
            for (e, r) in el.iter().zip(rl) {
                child_status.push(compare_ast_node(source, e, r.into())?);
            }
            let diff_scope = artificial_diff_scope(emacs_field, child_status)?;
            return Ok(ComparePropertiesResult::DiffEntry(diff_scope));
        }
    }
    Ok(ComparePropertiesResult::NoChange)
}