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use crate::{
    config::InlayHintsConfig,
    core::{
        session::Session,
        token::{get_range_from_span, TypedAstToken},
    },
};
use std::sync::Arc;
use sway_core::{language::ty::TyDecl, type_system::TypeInfo, Engines};
use sway_types::Spanned;
use tower_lsp::lsp_types::{self, Range, Url};

// Future PR's will add more kinds
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum InlayKind {
    TypeHint,
}

#[derive(Debug)]
pub struct InlayHint {
    pub range: Range,
    pub kind: InlayKind,
    pub label: String,
}

pub(crate) fn inlay_hints(
    session: Arc<Session>,
    uri: &Url,
    range: &Range,
    config: &InlayHintsConfig,
) -> Option<Vec<lsp_types::InlayHint>> {
    // 1. Loop through all our tokens and filter out all tokens that aren't TypedVariableDeclaration tokens
    // 2. Also filter out all tokens that have a span that fall outside of the provided range
    // 3. Filter out all variable tokens that have a type_ascription
    // 4. Look up the type id for the remaining tokens
    // 5. Convert the type into a string
    if !config.type_hints {
        return None;
    }

    let type_engine = session.type_engine.read();
    let decl_engine = session.decl_engine.read();
    let engines = Engines::new(&type_engine, &decl_engine);

    let hints: Vec<lsp_types::InlayHint> = session
        .token_map()
        .tokens_for_file(uri)
        .filter_map(|(_, token)| {
            token.typed.as_ref().and_then(|t| match t {
                TypedAstToken::TypedDeclaration(TyDecl::VariableDecl(var_decl)) => {
                    match var_decl.type_ascription.call_path_tree {
                        Some(_) => None,
                        None => {
                            let var_range = get_range_from_span(&var_decl.name.span());
                            if var_range.start >= range.start && var_range.end <= range.end {
                                Some(var_decl.clone())
                            } else {
                                None
                            }
                        }
                    }
                }
                _ => None,
            })
        })
        .filter_map(|var| {
            let type_info = type_engine.get(var.type_ascription.type_id);
            match type_info {
                TypeInfo::Unknown | TypeInfo::UnknownGeneric { .. } => None,
                _ => Some(var),
            }
        })
        .map(|var| {
            let range = get_range_from_span(&var.name.span());
            let kind = InlayKind::TypeHint;
            let label = format!("{}", engines.help_out(var.type_ascription));
            let inlay_hint = InlayHint { range, kind, label };
            self::inlay_hint(config.render_colons, inlay_hint)
        })
        .collect();

    Some(hints)
}

fn inlay_hint(render_colons: bool, inlay_hint: InlayHint) -> lsp_types::InlayHint {
    lsp_types::InlayHint {
        position: match inlay_hint.kind {
            // after annotated thing
            InlayKind::TypeHint => inlay_hint.range.end,
        },
        label: lsp_types::InlayHintLabel::String(match inlay_hint.kind {
            InlayKind::TypeHint if render_colons => format!(": {}", inlay_hint.label),
            _ => inlay_hint.label,
        }),
        kind: match inlay_hint.kind {
            InlayKind::TypeHint => Some(lsp_types::InlayHintKind::TYPE),
        },
        tooltip: None,
        padding_left: Some(match inlay_hint.kind {
            InlayKind::TypeHint => !render_colons,
        }),
        padding_right: Some(match inlay_hint.kind {
            InlayKind::TypeHint => false,
        }),
        text_edits: None,
        data: None,
    }
}