use std::vec;

use cairo_lang_defs::patcher::PatchBuilder;
use cairo_lang_defs::plugin::{MacroPlugin, PluginDiagnostic, PluginGeneratedFile, PluginResult};
use cairo_lang_filesystem::cfg::{Cfg, CfgSet};
use cairo_lang_syntax::attribute::structured::{
    Attribute, AttributeArg, AttributeArgVariant, AttributeStructurize,
};
use cairo_lang_syntax::node::db::SyntaxGroup;
use cairo_lang_syntax::node::helpers::QueryAttrs;
use cairo_lang_syntax::node::{ast, Terminal, TypedSyntaxNode};
use cairo_lang_utils::try_extract_matches;

/// Plugin that enables ignoring modules not involved in the current config.
/// Mostly useful for marking test modules to prevent usage of their functionality out of tests,
/// and reduce compilation time when the tests data isn't required.
#[derive(Debug, Default)]
#[non_exhaustive]
pub struct ConfigPlugin;

const CFG_ATTR: &str = "cfg";

impl MacroPlugin for ConfigPlugin {
    fn generate_code(&self, db: &dyn SyntaxGroup, item_ast: ast::ModuleItem) -> PluginResult {
        let cfg_set = db.cfg_set();
        let mut diagnostics = vec![];
        if should_drop(db, &cfg_set, &item_ast, &mut diagnostics) {
            PluginResult { code: None, diagnostics, remove_original_item: true }
        } else if let Some(builder) =
            handle_undropped_item(db, &cfg_set, item_ast, &mut diagnostics)
        {
            PluginResult {
                code: Some(PluginGeneratedFile {
                    name: "config".into(),
                    content: builder.code,
                    code_mappings: builder.code_mappings,
                    aux_data: None,
                }),
                diagnostics,
                remove_original_item: true,
            }
        } else {
            PluginResult { code: None, diagnostics, remove_original_item: false }
        }
    }

    fn declared_attributes(&self) -> Vec<String> {
        vec![CFG_ATTR.to_string()]
    }
}

/// Handles an item that is not dropped from the AST completely due to not matching the config.
/// In case it includes dropped elements and needs to be rewritten, it returns the appropriate
/// PatchBuilder. Otherwise returns `None`, and it won't be rewritten or dropped.
fn handle_undropped_item<'a>(
    db: &'a dyn SyntaxGroup,
    cfg_set: &CfgSet,
    item_ast: ast::ModuleItem,
    diagnostics: &mut Vec<PluginDiagnostic>,
) -> Option<PatchBuilder<'a>> {
    match item_ast {
        ast::ModuleItem::Trait(trait_item) => {
            let body = try_extract_matches!(trait_item.body(db), ast::MaybeTraitBody::Some)?;
            let items =
                get_kept_items_nodes(db, cfg_set, &body.items(db).elements(db), diagnostics)?;
            let mut builder = PatchBuilder::new(db);
            builder.add_node(trait_item.attributes(db).as_syntax_node());
            builder.add_node(trait_item.trait_kw(db).as_syntax_node());
            builder.add_node(trait_item.name(db).as_syntax_node());
            builder.add_node(trait_item.generic_params(db).as_syntax_node());
            builder.add_node(body.lbrace(db).as_syntax_node());
            for item in items {
                builder.add_node(item);
            }
            builder.add_node(body.rbrace(db).as_syntax_node());
            Some(builder)
        }
        ast::ModuleItem::Impl(impl_item) => {
            let body = try_extract_matches!(impl_item.body(db), ast::MaybeImplBody::Some)?;
            let items =
                get_kept_items_nodes(db, cfg_set, &body.items(db).elements(db), diagnostics)?;
            let mut builder = PatchBuilder::new(db);
            builder.add_node(impl_item.attributes(db).as_syntax_node());
            builder.add_node(impl_item.impl_kw(db).as_syntax_node());
            builder.add_node(impl_item.name(db).as_syntax_node());
            builder.add_node(impl_item.generic_params(db).as_syntax_node());
            builder.add_node(impl_item.of_kw(db).as_syntax_node());
            builder.add_node(impl_item.trait_path(db).as_syntax_node());
            builder.add_node(body.lbrace(db).as_syntax_node());
            for item in items {
                builder.add_node(item);
            }
            builder.add_node(body.rbrace(db).as_syntax_node());
            Some(builder)
        }
        _ => None,
    }
}

/// Gets the list of items that should be kept in the AST.
/// Returns `None` if all items should be kept.
fn get_kept_items_nodes<Item: QueryAttrs + TypedSyntaxNode>(
    db: &dyn SyntaxGroup,
    cfg_set: &CfgSet,
    all_items: &[Item],
    diagnostics: &mut Vec<PluginDiagnostic>,
) -> Option<Vec<cairo_lang_syntax::node::SyntaxNode>> {
    let mut any_dropped = false;
    let mut kept_items_nodes = vec![];
    for item in all_items {
        if should_drop(db, cfg_set, item, diagnostics) {
            any_dropped = true;
        } else {
            kept_items_nodes.push(item.as_syntax_node());
        }
    }
    if any_dropped { Some(kept_items_nodes) } else { None }
}

/// Check if the given item should be dropped from the AST.
fn should_drop<Item: QueryAttrs>(
    db: &dyn SyntaxGroup,
    cfg_set: &CfgSet,
    item: &Item,
    diagnostics: &mut Vec<PluginDiagnostic>,
) -> bool {
    item.query_attr(db, CFG_ATTR).into_iter().any(|attr| {
        matches!(
            parse_predicate(db, attr.structurize(db), diagnostics),
            Some(pattern) if !cfg_set.is_superset(&pattern)
        )
    })
}

/// Parse `#[cfg(...)]` attribute arguments as a predicate matching [`Cfg`] items.
fn parse_predicate(
    db: &dyn SyntaxGroup,
    attr: Attribute,
    diagnostics: &mut Vec<PluginDiagnostic>,
) -> Option<CfgSet> {
    attr
        .args
        .into_iter()
        .map(|arg| parse_predicate_item(db, arg, diagnostics))
        // NOTE: Try to parse each item eagerly, so that we will report any possible issues for all
        //   arguments at once. Take into account that Rust's `Iterator::collect::<Option<_>>`
        //   by itself would stop collection on first `None`.
        .collect::<Vec<_>>()
        .into_iter()
        .collect::<Option<Vec<Cfg>>>()
        .map(CfgSet::from_iter)
}

/// Parse single `#[cfg(...)]` attribute argument as a [`Cfg`] item.
fn parse_predicate_item(
    db: &dyn SyntaxGroup,
    arg: AttributeArg,
    diagnostics: &mut Vec<PluginDiagnostic>,
) -> Option<Cfg> {
    match arg.variant {
        AttributeArgVariant::FieldInitShorthand { .. } => {
            diagnostics.push(PluginDiagnostic::error(
                arg.arg_stable_ptr.untyped(),
                "This attribute does not support field initialization shorthands.".into(),
            ));
            None
        }
        AttributeArgVariant::Named { name, value, value_stable_ptr, .. } => {
            let value = match value {
                ast::Expr::ShortString(terminal) => terminal.string_value(db).unwrap_or_default(),
                ast::Expr::String(terminal) => terminal.string_value(db).unwrap_or_default(),
                _ => {
                    diagnostics.push(PluginDiagnostic::error(
                        value_stable_ptr.untyped(),
                        "Expected a string/short-string literal.".into(),
                    ));
                    return None;
                }
            };

            Some(Cfg::kv(name, value))
        }
        AttributeArgVariant::Unnamed { value, value_stable_ptr, .. } => {
            let ast::Expr::Path(path) = value else {
                diagnostics.push(PluginDiagnostic::error(
                    value_stable_ptr.untyped(),
                    "Expected identifier.".into(),
                ));
                return None;
            };
            let [ast::PathSegment::Simple(segment)] = &path.elements(db)[..] else {
                diagnostics.push(PluginDiagnostic::error(
                    value_stable_ptr.untyped(),
                    "Expected simple path.".into(),
                ));
                return None;
            };
            let key = segment.ident(db).text(db);
            Some(Cfg::name(key))
        }
    }
}