use syntax::{
    ast::{
        self,
        edit::{AstNodeEdit, IndentLevel},
    },
    AstNode, SyntaxKind, TextRange, T,
};

use crate::{utils::unwrap_trivial_block, AssistContext, AssistId, AssistKind, Assists};

// Assist: unwrap_block
//
// This assist removes if...else, for, while and loop control statements to just keep the body.
//
// ```
// fn foo() {
//     if true {$0
//         println!("foo");
//     }
// }
// ```
// ->
// ```
// fn foo() {
//     println!("foo");
// }
// ```
pub(crate) fn unwrap_block(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
    let assist_id = AssistId("unwrap_block", AssistKind::RefactorRewrite);
    let assist_label = "Unwrap block";

    let l_curly_token = ctx.find_token_syntax_at_offset(T!['{'])?;
    let mut block = ast::BlockExpr::cast(l_curly_token.parent()?)?;
    let target = block.syntax().text_range();
    let mut parent = block.syntax().parent()?;
    if ast::MatchArm::can_cast(parent.kind()) {
        parent = parent.ancestors().find(|it| ast::MatchExpr::can_cast(it.kind()))?
    }

    if matches!(parent.kind(), SyntaxKind::BLOCK_EXPR | SyntaxKind::EXPR_STMT) {
        return acc.add(assist_id, assist_label, target, |builder| {
            builder.replace(block.syntax().text_range(), update_expr_string(block.to_string()));
        });
    }

    let parent = ast::Expr::cast(parent)?;

    match parent.clone() {
        ast::Expr::ForExpr(_) | ast::Expr::WhileExpr(_) | ast::Expr::LoopExpr(_) => (),
        ast::Expr::MatchExpr(_) => block = block.dedent(IndentLevel(1)),
        ast::Expr::IfExpr(if_expr) => {
            let then_branch = if_expr.then_branch()?;
            if then_branch == block {
                if let Some(ancestor) = if_expr.syntax().parent().and_then(ast::IfExpr::cast) {
                    // For `else if` blocks
                    let ancestor_then_branch = ancestor.then_branch()?;

                    return acc.add(assist_id, assist_label, target, |edit| {
                        let range_to_del_else_if = TextRange::new(
                            ancestor_then_branch.syntax().text_range().end(),
                            l_curly_token.text_range().start(),
                        );
                        let range_to_del_rest = TextRange::new(
                            then_branch.syntax().text_range().end(),
                            if_expr.syntax().text_range().end(),
                        );

                        edit.delete(range_to_del_rest);
                        edit.delete(range_to_del_else_if);
                        edit.replace(
                            target,
                            update_expr_string_without_newline(then_branch.to_string()),
                        );
                    });
                }
            } else {
                return acc.add(assist_id, assist_label, target, |edit| {
                    let range_to_del = TextRange::new(
                        then_branch.syntax().text_range().end(),
                        l_curly_token.text_range().start(),
                    );

                    edit.delete(range_to_del);
                    edit.replace(target, update_expr_string_without_newline(block.to_string()));
                });
            }
        }
        _ => return None,
    };

    let unwrapped = unwrap_trivial_block(block);
    acc.add(assist_id, assist_label, target, |builder| {
        builder.replace(parent.syntax().text_range(), update_expr_string(unwrapped.to_string()));
    })
}

fn update_expr_string(expr_string: String) -> String {
    update_expr_string_with_pat(expr_string, &[' ', '\n'])
}

fn update_expr_string_without_newline(expr_string: String) -> String {
    update_expr_string_with_pat(expr_string, &[' '])
}

fn update_expr_string_with_pat(expr_str: String, whitespace_pat: &[char]) -> String {
    // Remove leading whitespace, index [1..] to remove the leading '{',
    // then continue to remove leading whitespace.
    let expr_str =
        expr_str.trim_start_matches(whitespace_pat)[1..].trim_start_matches(whitespace_pat);

    // Remove trailing whitespace, index [..expr_str.len() - 1] to remove the trailing '}',
    // then continue to remove trailing whitespace.
    let expr_str = expr_str.trim_end_matches(whitespace_pat);
    let expr_str = expr_str[..expr_str.len() - 1].trim_end_matches(whitespace_pat);

    expr_str
        .lines()
        .map(|line| line.replacen("    ", "", 1)) // Delete indentation
        .collect::<Vec<String>>()
        .join("\n")
}

#[cfg(test)]
mod tests {
    use crate::tests::{check_assist, check_assist_not_applicable};

    use super::*;

    #[test]
    fn unwrap_tail_expr_block() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    $0{
        92
    }
}
"#,
            r#"
fn main() {
    92
}
"#,
        )
    }

    #[test]
    fn unwrap_stmt_expr_block() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    $0{
        92;
    }
    ()
}
"#,
            r#"
fn main() {
    92;
    ()
}
"#,
        );
        // Pedantically, we should add an `;` here...
        check_assist(
            unwrap_block,
            r#"
fn main() {
    $0{
        92
    }
    ()
}
"#,
            r#"
fn main() {
    92
    ()
}
"#,
        );
    }

    #[test]
    fn simple_if() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    bar();
    if true {$0
        foo();

        // comment
        bar();
    } else {
        println!("bar");
    }
}
"#,
            r#"
fn main() {
    bar();
    foo();

    // comment
    bar();
}
"#,
        );
    }

    #[test]
    fn simple_if_else() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    bar();
    if true {
        foo();

        // comment
        bar();
    } else {$0
        println!("bar");
    }
}
"#,
            r#"
fn main() {
    bar();
    if true {
        foo();

        // comment
        bar();
    }
    println!("bar");
}
"#,
        );
    }

    #[test]
    fn simple_if_else_if() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {$0
        println!("bar");
    } else {
        println!("foo");
    }
}
"#,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    }
    println!("bar");
}
"#,
        );
    }

    #[test]
    fn simple_if_else_if_nested() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {
        println!("bar");
    } else if true {$0
        println!("foo");
    }
}
"#,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {
        println!("bar");
    }
    println!("foo");
}
"#,
        );
    }

    #[test]
    fn simple_if_else_if_nested_else() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {
        println!("bar");
    } else if true {
        println!("foo");
    } else {$0
        println!("else");
    }
}
"#,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {
        println!("bar");
    } else if true {
        println!("foo");
    }
    println!("else");
}
"#,
        );
    }

    #[test]
    fn simple_if_else_if_nested_middle() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {
        println!("bar");
    } else if true {$0
        println!("foo");
    } else {
        println!("else");
    }
}
"#,
            r#"
fn main() {
    // bar();
    if true {
        println!("true");

        // comment
        // bar();
    } else if false {
        println!("bar");
    }
    println!("foo");
}
"#,
        );
    }

    #[test]
    fn simple_if_bad_cursor_position() {
        check_assist_not_applicable(
            unwrap_block,
            r#"
fn main() {
    bar();$0
    if true {
        foo();

        // comment
        bar();
    } else {
        println!("bar");
    }
}
"#,
        );
    }

    #[test]
    fn simple_for() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    for i in 0..5 {$0
        if true {
            foo();

            // comment
            bar();
        } else {
            println!("bar");
        }
    }
}
"#,
            r#"
fn main() {
    if true {
        foo();

        // comment
        bar();
    } else {
        println!("bar");
    }
}
"#,
        );
    }

    #[test]
    fn simple_if_in_for() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    for i in 0..5 {
        if true {$0
            foo();

            // comment
            bar();
        } else {
            println!("bar");
        }
    }
}
"#,
            r#"
fn main() {
    for i in 0..5 {
        foo();

        // comment
        bar();
    }
}
"#,
        );
    }

    #[test]
    fn simple_loop() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    loop {$0
        if true {
            foo();

            // comment
            bar();
        } else {
            println!("bar");
        }
    }
}
"#,
            r#"
fn main() {
    if true {
        foo();

        // comment
        bar();
    } else {
        println!("bar");
    }
}
"#,
        );
    }

    #[test]
    fn simple_while() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    while true {$0
        if true {
            foo();

            // comment
            bar();
        } else {
            println!("bar");
        }
    }
}
"#,
            r#"
fn main() {
    if true {
        foo();

        // comment
        bar();
    } else {
        println!("bar");
    }
}
"#,
        );
    }

    #[test]
    fn unwrap_match_arm() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    match rel_path {
        Ok(rel_path) => {$0
            let rel_path = RelativePathBuf::from_path(rel_path).ok()?;
            Some((*id, rel_path))
        }
        Err(_) => None,
    }
}
"#,
            r#"
fn main() {
    let rel_path = RelativePathBuf::from_path(rel_path).ok()?;
    Some((*id, rel_path))
}
"#,
        );
    }

    #[test]
    fn simple_if_in_while_bad_cursor_position() {
        check_assist_not_applicable(
            unwrap_block,
            r#"
fn main() {
    while true {
        if true {
            foo();$0

            // comment
            bar();
        } else {
            println!("bar");
        }
    }
}
"#,
        );
    }

    #[test]
    fn simple_single_line() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    {$0 0 }
}
"#,
            r#"
fn main() {
    0
}
"#,
        );
    }

    #[test]
    fn simple_nested_block() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    $0{
        {
            3
        }
    }
}
"#,
            r#"
fn main() {
    {
        3
    }
}
"#,
        );
    }

    #[test]
    fn nested_single_line() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    {$0 { println!("foo"); } }
}
"#,
            r#"
fn main() {
    { println!("foo"); }
}
"#,
        );

        check_assist(
            unwrap_block,
            r#"
fn main() {
    {$0 { 0 } }
}
"#,
            r#"
fn main() {
    { 0 }
}
"#,
        );
    }

    #[test]
    fn simple_if_single_line() {
        check_assist(
            unwrap_block,
            r#"
fn main() {
    if true {$0 /* foo */ foo() } else { bar() /* bar */}
}
"#,
            r#"
fn main() {
    /* foo */ foo()
}
"#,
        );
    }
}