use crate::{
    gather_all, gen_changelog_lint_list, gen_deprecated, gen_lint_group_list, gen_modules_list, gen_register_lint_list,
    replace_region_in_file, Lint, DOCS_LINK,
};
use std::fs;
use std::path::Path;

#[derive(Clone, Copy, PartialEq)]
pub enum UpdateMode {
    Check,
    Change,
}

/// Runs the `update_lints` command.
///
/// This updates various generated values from the lint source code.
///
/// `update_mode` indicates if the files should be updated or if updates should be checked for.
///
/// # Panics
///
/// Panics if a file path could not read from or then written to
#[allow(clippy::too_many_lines)]
pub fn run(update_mode: UpdateMode) {
    let lint_list: Vec<Lint> = gather_all().collect();

    let internal_lints = Lint::internal_lints(&lint_list);
    let deprecated_lints = Lint::deprecated_lints(&lint_list);
    let usable_lints = Lint::usable_lints(&lint_list);
    let mut sorted_usable_lints = usable_lints.clone();
    sorted_usable_lints.sort_by_key(|lint| lint.name.clone());

    let usable_lint_count = round_to_fifty(usable_lints.len());

    let mut file_change = false;

    file_change |= replace_region_in_file(
        Path::new("README.md"),
        &format!(
            r#"\[There are over \d+ lints included in this crate!\]\({}\)"#,
            DOCS_LINK
        ),
        "",
        true,
        update_mode == UpdateMode::Change,
        || {
            vec![format!(
                "[There are over {} lints included in this crate!]({})",
                usable_lint_count, DOCS_LINK
            )]
        },
    )
    .changed;

    file_change |= replace_region_in_file(
        Path::new("CHANGELOG.md"),
        "<!-- begin autogenerated links to lint list -->",
        "<!-- end autogenerated links to lint list -->",
        false,
        update_mode == UpdateMode::Change,
        || gen_changelog_lint_list(usable_lints.iter().chain(deprecated_lints.iter())),
    )
    .changed;

    if file_change && update_mode == UpdateMode::Check {
        exit_with_failure();
    }

    for (name, lines) in [
        ("mods", gen_modules_list(usable_lints.iter())),
        ("deprecated", gen_deprecated(deprecated_lints.iter())),
        (
            "register_lints",
            gen_register_lint_list(internal_lints.iter(), usable_lints.iter()),
        ),
        ("register_all", {
            let all_group_lints = usable_lints.iter().filter(|l| {
                matches!(
                    &*l.group,
                    "correctness" | "suspicious" | "style" | "complexity" | "perf"
                )
            });

            gen_lint_group_list("all", all_group_lints)
        }),
    ] {
        process_file(&format!("clippy_lints/src/lib.{}.rs", name), update_mode, &lines[..]);
    }

    for (lint_group, lints) in Lint::by_lint_group(usable_lints.into_iter().chain(internal_lints)) {
        process_file(
            &format!("clippy_lints/src/lib.register_{}.rs", lint_group),
            update_mode,
            &gen_lint_group_list(&lints.get(0).expect("group non-empty").group, lints.iter())[..],
        );
    }
}

pub fn print_lints() {
    let lint_list: Vec<Lint> = gather_all().collect();
    let usable_lints = Lint::usable_lints(&lint_list);
    let usable_lint_count = usable_lints.len();
    let grouped_by_lint_group = Lint::by_lint_group(usable_lints.into_iter());

    for (lint_group, mut lints) in grouped_by_lint_group {
        if lint_group == "Deprecated" {
            continue;
        }
        println!("\n## {}", lint_group);

        lints.sort_by_key(|l| l.name.clone());

        for lint in lints {
            println!("* [{}]({}#{}) ({})", lint.name, DOCS_LINK, lint.name, lint.desc);
        }
    }

    println!("there are {} lints", usable_lint_count);
}

fn round_to_fifty(count: usize) -> usize {
    count / 50 * 50
}

fn process_file(path: impl AsRef<Path>, update_mode: UpdateMode, new_lines: &[String]) {
    let mut new_content = "// This file was generated by `cargo dev update_lints`.\n\
                       // Use that command to update this file and do not edit by hand.\n\
                       // Manual edits will be overwritten.\n\n"
        .to_string();
    new_content.push_str(&new_lines.join("\n"));

    if update_mode == UpdateMode::Check {
        let old_content =
            fs::read_to_string(&path).unwrap_or_else(|e| panic!("Cannot read from {}: {}", path.as_ref().display(), e));
        if new_content != old_content {
            exit_with_failure();
        }
    } else {
        fs::write(&path, new_content.as_bytes())
            .unwrap_or_else(|e| panic!("Cannot write to {}: {}", path.as_ref().display(), e));
    }
}

fn exit_with_failure() {
    println!(
        "Not all lints defined properly. \
                 Please run `cargo dev update_lints` to make sure all lints are defined properly."
    );
    std::process::exit(1);
}