//! Perform basic linting on source code.
//! What is implemented here affects subsequent optimizations,
//! and `erg_linter` does linting that does not affect optimizations.

#[allow(unused_imports)]
use erg_common::log;
use erg_common::traits::{Locational, Runnable, Stream};
use erg_common::Str;

use crate::ty::{HasType, Type};

use crate::error::{LowerError, LowerResult, LowerWarning, LowerWarnings, SingleLowerResult};
use crate::hir;
use crate::lower::ASTLowerer;
use crate::varinfo::VarInfo;

impl ASTLowerer {
    pub(crate) fn var_result_t_check(
        &self,
        loc: &impl Locational,
        name: &Str,
        expect: &Type,
        found: &Type,
    ) -> SingleLowerResult<()> {
        self.module
            .context
            .sub_unify(found, expect, loc, Some(name))
            .map_err(|_| {
                LowerError::type_mismatch_error(
                    self.cfg().input.clone(),
                    line!() as usize,
                    loc.loc(),
                    self.module.context.caused_by(),
                    name,
                    None,
                    expect,
                    found,
                    None, // self.ctx.get_candidates(found),
                    self.module
                        .context
                        .get_simple_type_mismatch_hint(expect, found),
                )
            })
    }

    pub(crate) fn warn_unused_expr(&mut self, module: &hir::Module, mode: &str) {
        if mode == "eval" {
            return;
        }
        for chunk in module.iter() {
            if let Err(warns) = self.expr_use_check(chunk) {
                self.warns.extend(warns);
            }
        }
    }

    /// OK: exec `i: Int`
    /// OK: exec `i: Int = 1`
    /// NG: exec `1 + 2`
    /// OK: exec `None`
    fn expr_use_check(&self, expr: &hir::Expr) -> LowerResult<()> {
        if !expr.ref_t().is_nonelike() && !expr.is_type_asc() && !expr.is_doc_comment() {
            if expr.ref_t().is_subr() {
                Err(LowerWarnings::from(
                    LowerWarning::unused_subroutine_warning(
                        self.cfg().input.clone(),
                        line!() as usize,
                        expr,
                        String::from(&self.module.context.name[..]),
                    ),
                ))
            } else {
                Err(LowerWarnings::from(LowerWarning::unused_expr_warning(
                    self.cfg().input.clone(),
                    line!() as usize,
                    expr,
                    String::from(&self.module.context.name[..]),
                )))
            }
        } else {
            self.block_use_check(expr)
        }
    }

    fn block_use_check(&self, expr: &hir::Expr) -> LowerResult<()> {
        let mut warns = LowerWarnings::empty();
        match expr {
            hir::Expr::Def(def) => {
                let last = def.body.block.len() - 1;
                for (i, chunk) in def.body.block.iter().enumerate() {
                    if i == last {
                        if let Err(ws) = self.block_use_check(chunk) {
                            warns.extend(ws);
                        }
                        break;
                    }
                    if let Err(ws) = self.expr_use_check(chunk) {
                        warns.extend(ws);
                    }
                }
            }
            hir::Expr::Lambda(lambda) => {
                let last = lambda.body.len() - 1;
                for (i, chunk) in lambda.body.iter().enumerate() {
                    if i == last {
                        if let Err(ws) = self.block_use_check(chunk) {
                            warns.extend(ws);
                        }
                        break;
                    }
                    if let Err(ws) = self.expr_use_check(chunk) {
                        warns.extend(ws);
                    }
                }
            }
            hir::Expr::ClassDef(class_def) => {
                for chunk in class_def.methods.iter() {
                    if let Err(ws) = self.expr_use_check(chunk) {
                        warns.extend(ws);
                    }
                }
            }
            hir::Expr::PatchDef(patch_def) => {
                for chunk in patch_def.methods.iter() {
                    if let Err(ws) = self.expr_use_check(chunk) {
                        warns.extend(ws);
                    }
                }
            }
            hir::Expr::Call(call) => {
                for arg in call.args.pos_args.iter() {
                    if let Err(ws) = self.block_use_check(&arg.expr) {
                        warns.extend(ws);
                    }
                }
                if let Some(var_args) = &call.args.var_args {
                    if let Err(ws) = self.block_use_check(&var_args.expr) {
                        warns.extend(ws);
                    }
                }
                for arg in call.args.kw_args.iter() {
                    if let Err(ws) = self.block_use_check(&arg.expr) {
                        warns.extend(ws);
                    }
                }
            }
            // TODO: unary, binary, array, ...
            _ => {}
        }
        if warns.is_empty() {
            Ok(())
        } else {
            Err(warns)
        }
    }

    pub(crate) fn inc_ref<L: Locational>(&self, vi: &VarInfo, name: &L) {
        self.module.context.inc_ref(vi, name);
    }

    pub(crate) fn warn_unused_vars(&mut self, mode: &str) {
        if mode == "eval" {
            return;
        }
        for (referee, value) in self.module.context.index().iter() {
            let code = referee.code();
            let name = code.as_ref().map(|s| &s[..]).unwrap_or("");
            let name_is_auto = name == "_"; // || name.starts_with(['%']);
            if value.referrers.is_empty() && value.vi.vis.is_private() && !name_is_auto {
                let input = referee
                    .module
                    .as_ref()
                    .map_or(self.input().clone(), |path| path.as_path().into());
                let warn = LowerWarning::unused_warning(
                    input,
                    line!() as usize,
                    referee.loc,
                    name,
                    self.module.context.caused_by(),
                );
                self.warns.push(warn);
            }
        }
    }
}