use std::collections::HashSet;

use rustc_hash::FxHashSet;

use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
use ruff_macros::{derive_message_formats, violation};
use ruff_python_ast::comparable::ComparableExpr;
use ruff_python_ast::{self as ast, Expr, ExprContext};
use ruff_python_semantic::analyze::typing::traverse_literal;
use ruff_text_size::{Ranged, TextRange};

use crate::checkers::ast::Checker;

/// ## What it does
/// Checks for duplicate members in a `typing.Literal[]` slice.
///
/// ## Why is this bad?
/// Duplicate literal members are redundant and should be removed.
///
/// ## Example
/// ```python
/// foo: Literal["a", "b", "a"]
/// ```
///
/// Use instead:
/// ```python
/// foo: Literal["a", "b"]
/// ```
///
/// ## Fix safety
/// This rule's fix is marked as safe; however, the fix will flatten nested
/// literals into a single top-level literal.
///
/// ## References
/// - [Python documentation: `typing.Literal`](https://docs.python.org/3/library/typing.html#typing.Literal)
#[violation]
pub struct DuplicateLiteralMember {
    duplicate_name: String,
}

impl AlwaysFixableViolation for DuplicateLiteralMember {
    #[derive_message_formats]
    fn message(&self) -> String {
        format!("Duplicate literal member `{}`", self.duplicate_name)
    }

    fn fix_title(&self) -> String {
        "Remove duplicates".to_string()
    }
}

/// PYI062
pub(crate) fn duplicate_literal_member<'a>(checker: &mut Checker, expr: &'a Expr) {
    let mut seen_nodes: HashSet<ComparableExpr<'_>, _> = FxHashSet::default();
    let mut unique_nodes: Vec<&Expr> = Vec::new();
    let mut diagnostics: Vec<Diagnostic> = Vec::new();

    // Adds a member to `literal_exprs` if it is a `Literal` annotation
    let mut check_for_duplicate_members = |expr: &'a Expr, _: &'a Expr| {
        // If we've already seen this literal member, raise a violation.
        if seen_nodes.insert(expr.into()) {
            unique_nodes.push(expr);
        } else {
            diagnostics.push(Diagnostic::new(
                DuplicateLiteralMember {
                    duplicate_name: checker.generator().expr(expr),
                },
                expr.range(),
            ));
        }
    };

    // Traverse the literal, collect all diagnostic members.
    traverse_literal(&mut check_for_duplicate_members, checker.semantic(), expr);

    // If there's at least one diagnostic, create a fix to remove the duplicate members.
    if !diagnostics.is_empty() {
        if let Expr::Subscript(subscript) = expr {
            let subscript = Expr::Subscript(ast::ExprSubscript {
                slice: Box::new(if let [elt] = unique_nodes.as_slice() {
                    (*elt).clone()
                } else {
                    Expr::Tuple(ast::ExprTuple {
                        elts: unique_nodes.into_iter().cloned().collect(),
                        range: TextRange::default(),
                        ctx: ExprContext::Load,
                        parenthesized: false,
                    })
                }),
                value: subscript.value.clone(),
                range: TextRange::default(),
                ctx: ExprContext::Load,
            });
            let fix = Fix::safe_edit(Edit::range_replacement(
                checker.generator().expr(&subscript),
                expr.range(),
            ));
            for diagnostic in &mut diagnostics {
                diagnostic.set_fix(fix.clone());
            }
        }
    }

    checker.diagnostics.append(&mut diagnostics);
}
