//! The `search` module.
//!
//! Focused on providing search functionalities within crates. This module might contain
//! implementations for searching through crate contents, such as source code files, documentation,
//! and other relevant data. It could include various search algorithms and data structures optimized
//! for quick and efficient search operations, like `SearchIndex`.
//!
use fnv::FnvHashMap;
use serde::{Deserialize, Serialize};
use std::num::NonZeroUsize;
use std::path::Path;
use std::sync::Arc;
use syn::spanned::Spanned;
use syn::{Attribute, ItemEnum, ItemFn, ItemImpl, ItemMacro, ItemStruct, ItemTrait};

use crate::{Item, ItemQuery, ItemType};

/// A mutable search index containing categorized items for searching within a crate.
///
/// This struct stores various items like structs, enums, traits, etc., in categorized hash maps,
/// facilitating efficient search operations.
///
#[derive(Debug, Default, Serialize, Deserialize)]
pub struct SearchIndexMut {
    pub structs: FnvHashMap<String, Vec<Item>>,
    pub enums: FnvHashMap<String, Vec<Item>>,
    pub traits: FnvHashMap<String, Vec<Item>>,
    pub impl_types: FnvHashMap<String, Vec<Item>>,
    pub impl_trait_for_types: FnvHashMap<String, Vec<Item>>,
    pub macros: FnvHashMap<String, Vec<Item>>,
    pub attribute_macros: FnvHashMap<String, Vec<Item>>,
    pub functions: FnvHashMap<String, Vec<Item>>,
    pub type_aliases: FnvHashMap<String, Vec<Item>>,
}

impl SearchIndexMut {
    /// Searches for items within the index based on the provided query.
    ///
    pub fn search(&self, query: &ItemQuery) -> Vec<Item> {
        let ItemQuery { type_, query, path } = query;
        let query = query.to_lowercase();
        let path = path.as_ref().map(|p| p.as_path());
        match type_ {
            ItemType::All => {
                let mut all = Vec::new();
                all.extend(filter_items(&query, &self.structs, path));
                all.extend(filter_items(&query, &self.enums, path));
                all.extend(filter_items(&query, &self.traits, path));
                all.extend(filter_items(&query, &self.impl_types, path));
                all.extend(filter_items(&query, &self.impl_trait_for_types, path));
                all.extend(filter_items(&query, &self.macros, path));
                all.extend(filter_items(&query, &self.attribute_macros, path));
                all.extend(filter_items(&query, &self.functions, path));
                all.extend(filter_items(&query, &self.type_aliases, path));
                all
            }
            ItemType::Struct => filter_items(&query, &self.structs, path),
            ItemType::Enum => filter_items(&query, &self.enums, path),
            ItemType::Trait => filter_items(&query, &self.traits, path),
            ItemType::ImplType => filter_items(&query, &self.impl_types, path),
            ItemType::ImplTraitForType => filter_items(&query, &self.impl_trait_for_types, path),
            ItemType::Macro => filter_items(&query, &self.macros, path),
            ItemType::AttributeMacro => filter_items(&query, &self.attribute_macros, path),
            ItemType::Function => filter_items(&query, &self.functions, path),
            ItemType::TypeAlias => filter_items(&query, &self.type_aliases, path),
        }
    }
}

/// Filters items from a hashmap based on a query and optional path.
///
fn filter_items(
    query: &str,
    items: &FnvHashMap<String, Vec<Item>>,
    path: Option<&Path>,
) -> Vec<Item> {
    let flatten = items
        .iter()
        .filter(|(name, _)| name.contains(&query))
        .map(|(_, item)| item)
        .flatten();
    match path {
        None => flatten.cloned().collect::<Vec<Item>>(),
        Some(path) => flatten
            .filter(|item| item.file.starts_with(path))
            .cloned()
            .collect::<Vec<Item>>(),
    }
}

/// Shared immutable search index, used for efficient read access across multiple threads.
pub type SearchIndex = Arc<SearchIndexMut>;

impl SearchIndexMut {
    /// Freezes the mutable search index into an immutable one.
    ///
    pub fn freeze(self) -> SearchIndex {
        Arc::new(self)
    }
}

/// A builder for constructing a `SearchIndex`.
///
/// This struct facilitates the creation and population of a `SearchIndexMut`
/// by parsing Rust source files and adding items to the index.
#[derive(Debug, Default)]
pub struct SearchIndexBuilder {
    index: SearchIndexMut,
}

impl SearchIndexBuilder {
    /// Updates the search index with items parsed from a Rust source file.
    ///
    pub fn update<P: AsRef<Path>>(&mut self, file: P, content: &str) -> bool {
        let mut visitor = IndexVisitor::new(&mut self.index, file);
        if let Ok(ast) = syn::parse_file(content) {
            syn::visit::visit_file(&mut visitor, &ast);
            true
        } else {
            false
        }
    }

    /// Finalizes the construction of the `SearchIndex`.
    ///
    pub fn finish(self) -> SearchIndex {
        self.index.freeze()
    }
}

/// A visitor struct for traversing and indexing Rust syntax trees.
///
/// This struct is used in conjunction with `syn::visit::Visit` to extract items from Rust source files
/// and add them to a `SearchIndexMut`.
pub struct IndexVisitor<'i> {
    index: &'i mut SearchIndexMut,
    current_file: Arc<Path>,
}

impl<'i> IndexVisitor<'i> {
    /// Creates a new `IndexVisitor`.
    ///
    pub fn new<P: AsRef<Path>>(index: &'i mut SearchIndexMut, current_file: P) -> Self {
        IndexVisitor {
            index,
            current_file: Arc::from(current_file.as_ref()),
        }
    }

    fn create_item(
        &self,
        name: String,
        type_: ItemType,
        item_span: proc_macro2::Span,
        attrs: &[Attribute],
    ) -> Item {
        // 获取项的 span
        let mut start_line = item_span.start().line;
        let end_line = item_span.end().line;

        // 检查并调整起始行号以包含文档注释
        for attr in attrs {
            if attr.path().is_ident("doc") {
                let attr_span = attr.span();
                start_line = start_line.min(attr_span.start().line);
            }
        }

        let start_line = NonZeroUsize::new(start_line).unwrap_or(NonZeroUsize::MIN);
        let end_line = NonZeroUsize::new(end_line).unwrap_or(NonZeroUsize::MAX);

        Item {
            name,
            type_,
            file: self.current_file.clone(),
            line_range: start_line..=end_line,
        }
    }
}

impl<'i, 'ast> syn::visit::Visit<'ast> for IndexVisitor<'i> {
    fn visit_item_enum(&mut self, i: &'ast ItemEnum) {
        let name = i.ident.to_string();
        let item = self.create_item(name, ItemType::Enum, i.span(), &i.attrs);
        self.index
            .enums
            .entry(item.name.to_lowercase())
            .or_default()
            .push(item);
    }

    fn visit_item_fn(&mut self, i: &'ast ItemFn) {
        if is_attribute_macro(&i.attrs) {
            let name = i.sig.ident.to_string();
            let item = self.create_item(name, ItemType::AttributeMacro, i.span(), &i.attrs);
            self.index
                .attribute_macros
                .entry(item.name.to_lowercase())
                .or_default()
                .push(item);
        } else {
            let name = i.sig.ident.to_string();
            let item = self.create_item(name, ItemType::Function, i.span(), &i.attrs);
            self.index
                .functions
                .entry(item.name.to_lowercase())
                .or_default()
                .push(item);
        }
    }

    fn visit_item_impl(&mut self, i: &'ast ItemImpl) {
        let self_ty = &i.self_ty;

        match &i.trait_ {
            Some((_, path, _)) => {
                // impl Trait for Type
                let impl_name = format!(
                    "impl {} for {}",
                    quote::quote! { #path },
                    quote::quote! { #self_ty }
                );
                let item =
                    self.create_item(impl_name, ItemType::ImplTraitForType, i.span(), &i.attrs);
                self.index
                    .impl_trait_for_types
                    .entry(item.name.to_lowercase())
                    .or_default()
                    .push(item);
            }
            None => {
                // impl Type
                let impl_name = format!("impl {}", quote::quote! { #self_ty });
                let item = self.create_item(impl_name, ItemType::ImplType, i.span(), &i.attrs);
                self.index
                    .impl_types
                    .entry(item.name.to_lowercase())
                    .or_default()
                    .push(item);
            }
        };
    }

    fn visit_item_macro(&mut self, i: &'ast ItemMacro) {
        if let Some(ident) = &i.ident {
            let name = ident.to_string();
            let item = self.create_item(name, ItemType::Macro, i.span(), &i.attrs);
            self.index
                .macros
                .entry(item.name.to_lowercase())
                .or_default()
                .push(item);
        }
    }

    fn visit_item_struct(&mut self, i: &'ast ItemStruct) {
        let name = i.ident.to_string();
        let item = self.create_item(name, ItemType::Struct, i.span(), &i.attrs);
        self.index
            .structs
            .entry(item.name.to_lowercase())
            .or_default()
            .push(item);
    }

    fn visit_item_trait(&mut self, i: &'ast ItemTrait) {
        let name = i.ident.to_string();
        let item = self.create_item(name, ItemType::Trait, i.span(), &i.attrs);
        self.index
            .traits
            .entry(item.name.to_lowercase())
            .or_default()
            .push(item);
    }

    fn visit_item_type(&mut self, i: &'ast syn::ItemType) {
        let name = i.ident.to_string();
        let item = self.create_item(name, ItemType::TypeAlias, i.span(), &i.attrs);
        self.index
            .type_aliases
            .entry(item.name.to_lowercase())
            .or_default()
            .push(item);
    }
}

fn is_attribute_macro(attrs: &[Attribute]) -> bool {
    attrs.iter().any(|attr| {
        // check proc_macro_attribute
        attr.path().is_ident("proc_macro_attribute")
    })
}