use std::borrow::Cow;

use syntax::{ast, ast::IsString, AstToken, TextRange, TextSize};

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

// Assist: make_raw_string
//
// Adds `r#` to a plain string literal.
//
// ```
// fn main() {
//     "Hello,$0 World!";
// }
// ```
// ->
// ```
// fn main() {
//     r#"Hello, World!"#;
// }
// ```
pub(crate) fn make_raw_string(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
    let token = ctx.find_token_at_offset::<ast::String>()?;
    if token.is_raw() {
        return None;
    }
    let value = token.value()?;
    let target = token.syntax().text_range();
    acc.add(
        AssistId("make_raw_string", AssistKind::RefactorRewrite),
        "Rewrite as raw string",
        target,
        |edit| {
            let hashes = "#".repeat(required_hashes(&value).max(1));
            if matches!(value, Cow::Borrowed(_)) {
                // Avoid replacing the whole string to better position the cursor.
                edit.insert(token.syntax().text_range().start(), format!("r{hashes}"));
                edit.insert(token.syntax().text_range().end(), hashes);
            } else {
                edit.replace(token.syntax().text_range(), format!("r{hashes}\"{value}\"{hashes}"));
            }
        },
    )
}

// Assist: make_usual_string
//
// Turns a raw string into a plain string.
//
// ```
// fn main() {
//     r#"Hello,$0 "World!""#;
// }
// ```
// ->
// ```
// fn main() {
//     "Hello, \"World!\"";
// }
// ```
pub(crate) fn make_usual_string(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
    let token = ctx.find_token_at_offset::<ast::String>()?;
    if !token.is_raw() {
        return None;
    }
    let value = token.value()?;
    let target = token.syntax().text_range();
    acc.add(
        AssistId("make_usual_string", AssistKind::RefactorRewrite),
        "Rewrite as regular string",
        target,
        |edit| {
            // parse inside string to escape `"`
            let escaped = value.escape_default().to_string();
            if let Some(offsets) = token.quote_offsets() {
                if token.text()[offsets.contents - token.syntax().text_range().start()] == escaped {
                    edit.replace(offsets.quotes.0, "\"");
                    edit.replace(offsets.quotes.1, "\"");
                    return;
                }
            }

            edit.replace(token.syntax().text_range(), format!("\"{escaped}\""));
        },
    )
}

// Assist: add_hash
//
// Adds a hash to a raw string literal.
//
// ```
// fn main() {
//     r#"Hello,$0 World!"#;
// }
// ```
// ->
// ```
// fn main() {
//     r##"Hello, World!"##;
// }
// ```
pub(crate) fn add_hash(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
    let token = ctx.find_token_at_offset::<ast::String>()?;
    if !token.is_raw() {
        return None;
    }
    let text_range = token.syntax().text_range();
    let target = text_range;
    acc.add(AssistId("add_hash", AssistKind::Refactor), "Add #", target, |edit| {
        edit.insert(text_range.start() + TextSize::of('r'), "#");
        edit.insert(text_range.end(), "#");
    })
}

// Assist: remove_hash
//
// Removes a hash from a raw string literal.
//
// ```
// fn main() {
//     r#"Hello,$0 World!"#;
// }
// ```
// ->
// ```
// fn main() {
//     r"Hello, World!";
// }
// ```
pub(crate) fn remove_hash(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
    let token = ctx.find_token_at_offset::<ast::String>()?;
    if !token.is_raw() {
        return None;
    }

    let text = token.text();
    if !text.starts_with("r#") && text.ends_with('#') {
        return None;
    }

    let existing_hashes = text.chars().skip(1).take_while(|&it| it == '#').count();

    let text_range = token.syntax().text_range();
    let internal_text = &text[token.text_range_between_quotes()? - text_range.start()];

    if existing_hashes == required_hashes(internal_text) {
        cov_mark::hit!(cant_remove_required_hash);
        return None;
    }

    acc.add(AssistId("remove_hash", AssistKind::RefactorRewrite), "Remove #", text_range, |edit| {
        edit.delete(TextRange::at(text_range.start() + TextSize::of('r'), TextSize::of('#')));
        edit.delete(TextRange::new(text_range.end() - TextSize::of('#'), text_range.end()));
    })
}

fn required_hashes(s: &str) -> usize {
    let mut res = 0usize;
    for idx in s.match_indices('"').map(|(i, _)| i) {
        let (_, sub) = s.split_at(idx + 1);
        let n_hashes = sub.chars().take_while(|c| *c == '#').count();
        res = res.max(n_hashes + 1)
    }
    res
}

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

    use super::*;

    #[test]
    fn test_required_hashes() {
        assert_eq!(0, required_hashes("abc"));
        assert_eq!(0, required_hashes("###"));
        assert_eq!(1, required_hashes("\""));
        assert_eq!(2, required_hashes("\"#abc"));
        assert_eq!(0, required_hashes("#abc"));
        assert_eq!(3, required_hashes("#ab\"##c"));
        assert_eq!(5, required_hashes("#ab\"##\"####c"));
    }

    #[test]
    fn make_raw_string_target() {
        check_assist_target(
            make_raw_string,
            r#"
            fn f() {
                let s = $0"random\nstring";
            }
            "#,
            r#""random\nstring""#,
        );
    }

    #[test]
    fn make_raw_string_works() {
        check_assist(
            make_raw_string,
            r#"
fn f() {
    let s = $0"random\nstring";
}
"#,
            r##"
fn f() {
    let s = r#"random
string"#;
}
"##,
        )
    }

    #[test]
    fn make_raw_string_works_inside_macros() {
        check_assist(
            make_raw_string,
            r#"
            fn f() {
                format!($0"x = {}", 92)
            }
            "#,
            r##"
            fn f() {
                format!(r#"x = {}"#, 92)
            }
            "##,
        )
    }

    #[test]
    fn make_raw_string_hashes_inside_works() {
        check_assist(
            make_raw_string,
            r###"
fn f() {
    let s = $0"#random##\nstring";
}
"###,
            r####"
fn f() {
    let s = r#"#random##
string"#;
}
"####,
        )
    }

    #[test]
    fn make_raw_string_closing_hashes_inside_works() {
        check_assist(
            make_raw_string,
            r###"
fn f() {
    let s = $0"#random\"##\nstring";
}
"###,
            r####"
fn f() {
    let s = r###"#random"##
string"###;
}
"####,
        )
    }

    #[test]
    fn make_raw_string_nothing_to_unescape_works() {
        check_assist(
            make_raw_string,
            r#"
            fn f() {
                let s = $0"random string";
            }
            "#,
            r##"
            fn f() {
                let s = r#"random string"#;
            }
            "##,
        )
    }

    #[test]
    fn make_raw_string_not_works_on_partial_string() {
        check_assist_not_applicable(
            make_raw_string,
            r#"
            fn f() {
                let s = "foo$0
            }
            "#,
        )
    }

    #[test]
    fn make_usual_string_not_works_on_partial_string() {
        check_assist_not_applicable(
            make_usual_string,
            r#"
            fn main() {
                let s = r#"bar$0
            }
            "#,
        )
    }

    #[test]
    fn add_hash_target() {
        check_assist_target(
            add_hash,
            r#"
            fn f() {
                let s = $0r"random string";
            }
            "#,
            r#"r"random string""#,
        );
    }

    #[test]
    fn add_hash_works() {
        check_assist(
            add_hash,
            r#"
            fn f() {
                let s = $0r"random string";
            }
            "#,
            r##"
            fn f() {
                let s = r#"random string"#;
            }
            "##,
        )
    }

    #[test]
    fn add_more_hash_works() {
        check_assist(
            add_hash,
            r##"
            fn f() {
                let s = $0r#"random"string"#;
            }
            "##,
            r###"
            fn f() {
                let s = r##"random"string"##;
            }
            "###,
        )
    }

    #[test]
    fn add_hash_not_works() {
        check_assist_not_applicable(
            add_hash,
            r#"
            fn f() {
                let s = $0"random string";
            }
            "#,
        );
    }

    #[test]
    fn remove_hash_target() {
        check_assist_target(
            remove_hash,
            r##"
            fn f() {
                let s = $0r#"random string"#;
            }
            "##,
            r##"r#"random string"#"##,
        );
    }

    #[test]
    fn remove_hash_works() {
        check_assist(
            remove_hash,
            r##"fn f() { let s = $0r#"random string"#; }"##,
            r#"fn f() { let s = r"random string"; }"#,
        )
    }

    #[test]
    fn cant_remove_required_hash() {
        cov_mark::check!(cant_remove_required_hash);
        check_assist_not_applicable(
            remove_hash,
            r##"
            fn f() {
                let s = $0r#"random"str"ing"#;
            }
            "##,
        )
    }

    #[test]
    fn remove_more_hash_works() {
        check_assist(
            remove_hash,
            r###"
            fn f() {
                let s = $0r##"random string"##;
            }
            "###,
            r##"
            fn f() {
                let s = r#"random string"#;
            }
            "##,
        )
    }

    #[test]
    fn remove_hash_doesnt_work() {
        check_assist_not_applicable(remove_hash, r#"fn f() { let s = $0"random string"; }"#);
    }

    #[test]
    fn remove_hash_no_hash_doesnt_work() {
        check_assist_not_applicable(remove_hash, r#"fn f() { let s = $0r"random string"; }"#);
    }

    #[test]
    fn make_usual_string_target() {
        check_assist_target(
            make_usual_string,
            r##"
            fn f() {
                let s = $0r#"random string"#;
            }
            "##,
            r##"r#"random string"#"##,
        );
    }

    #[test]
    fn make_usual_string_works() {
        check_assist(
            make_usual_string,
            r##"
            fn f() {
                let s = $0r#"random string"#;
            }
            "##,
            r#"
            fn f() {
                let s = "random string";
            }
            "#,
        )
    }

    #[test]
    fn make_usual_string_with_quote_works() {
        check_assist(
            make_usual_string,
            r##"
            fn f() {
                let s = $0r#"random"str"ing"#;
            }
            "##,
            r#"
            fn f() {
                let s = "random\"str\"ing";
            }
            "#,
        )
    }

    #[test]
    fn make_usual_string_more_hash_works() {
        check_assist(
            make_usual_string,
            r###"
            fn f() {
                let s = $0r##"random string"##;
            }
            "###,
            r##"
            fn f() {
                let s = "random string";
            }
            "##,
        )
    }

    #[test]
    fn make_usual_string_not_works() {
        check_assist_not_applicable(
            make_usual_string,
            r#"
            fn f() {
                let s = $0"random string";
            }
            "#,
        );
    }
}