use std::{
    fmt, fs, mem,
    path::{Path, PathBuf},
};

use xshell::{cmd, Shell};

use crate::{flags, project_root};

pub(crate) mod assists_doc_tests;
pub(crate) mod diagnostics_docs;
mod grammar;
mod lints;

impl flags::Codegen {
    pub(crate) fn run(self, _sh: &Shell) -> anyhow::Result<()> {
        match self.codegen_type.unwrap_or_default() {
            flags::CodegenType::All => {
                diagnostics_docs::generate(self.check);
                assists_doc_tests::generate(self.check);
                // lints::generate(self.check) Updating clones the rust repo, so don't run it unless
                // explicitly asked for
            }
            flags::CodegenType::Grammar => grammar::generate(self.check),
            flags::CodegenType::AssistsDocTests => assists_doc_tests::generate(self.check),
            flags::CodegenType::DiagnosticsDocs => diagnostics_docs::generate(self.check),
            flags::CodegenType::LintDefinitions => lints::generate(self.check),
        }
        Ok(())
    }
}

fn list_rust_files(dir: &Path) -> Vec<PathBuf> {
    let mut res = list_files(dir);
    res.retain(|it| {
        it.file_name().unwrap_or_default().to_str().unwrap_or_default().ends_with(".rs")
    });
    res
}

fn list_files(dir: &Path) -> Vec<PathBuf> {
    let mut res = Vec::new();
    let mut work = vec![dir.to_path_buf()];
    while let Some(dir) = work.pop() {
        for entry in dir.read_dir().unwrap() {
            let entry = entry.unwrap();
            let file_type = entry.file_type().unwrap();
            let path = entry.path();
            let is_hidden =
                path.file_name().unwrap_or_default().to_str().unwrap_or_default().starts_with('.');
            if !is_hidden {
                if file_type.is_dir() {
                    work.push(path);
                } else if file_type.is_file() {
                    res.push(path);
                }
            }
        }
    }
    res
}

#[derive(Clone)]
pub(crate) struct CommentBlock {
    pub(crate) id: String,
    pub(crate) line: usize,
    pub(crate) contents: Vec<String>,
    is_doc: bool,
}

impl CommentBlock {
    fn extract(tag: &str, text: &str) -> Vec<CommentBlock> {
        assert!(tag.starts_with(char::is_uppercase));

        let tag = format!("{tag}:");
        let mut blocks = CommentBlock::extract_untagged(text);
        blocks.retain_mut(|block| {
            let first = block.contents.remove(0);
            let Some(id) = first.strip_prefix(&tag) else {
                return false;
            };

            if block.is_doc {
                panic!("Use plain (non-doc) comments with tags like {tag}:\n    {first}");
            }

            id.trim().clone_into(&mut block.id);
            true
        });
        blocks
    }

    fn extract_untagged(text: &str) -> Vec<CommentBlock> {
        let mut res = Vec::new();

        let lines = text.lines().map(str::trim_start);

        let dummy_block =
            CommentBlock { id: String::new(), line: 0, contents: Vec::new(), is_doc: false };
        let mut block = dummy_block.clone();
        for (line_num, line) in lines.enumerate() {
            match line.strip_prefix("//") {
                Some(mut contents) => {
                    if let Some('/' | '!') = contents.chars().next() {
                        contents = &contents[1..];
                        block.is_doc = true;
                    }
                    if let Some(' ') = contents.chars().next() {
                        contents = &contents[1..];
                    }
                    block.contents.push(contents.to_owned());
                }
                None => {
                    if !block.contents.is_empty() {
                        let block = mem::replace(&mut block, dummy_block.clone());
                        res.push(block);
                    }
                    block.line = line_num + 2;
                }
            }
        }
        if !block.contents.is_empty() {
            res.push(block);
        }
        res
    }
}

#[derive(Debug)]
pub(crate) struct Location {
    pub(crate) file: PathBuf,
    pub(crate) line: usize,
}

impl fmt::Display for Location {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let path = self.file.strip_prefix(project_root()).unwrap().display().to_string();
        let path = path.replace('\\', "/");
        let name = self.file.file_name().unwrap();
        write!(
            f,
            "https://github.com/rust-lang/rust-analyzer/blob/master/{}#L{}[{}]",
            path,
            self.line,
            name.to_str().unwrap()
        )
    }
}

fn ensure_rustfmt(sh: &Shell) {
    let version = cmd!(sh, "rustup run stable rustfmt --version").read().unwrap_or_default();
    if !version.contains("stable") {
        panic!(
            "Failed to run rustfmt from toolchain 'stable'. \
                 Please run `rustup component add rustfmt --toolchain stable` to install it.",
        );
    }
}

fn reformat(text: String) -> String {
    let sh = Shell::new().unwrap();
    ensure_rustfmt(&sh);
    let rustfmt_toml = project_root().join("rustfmt.toml");
    let mut stdout = cmd!(
        sh,
        "rustup run stable rustfmt --config-path {rustfmt_toml} --config fn_single_line=true"
    )
    .stdin(text)
    .read()
    .unwrap();
    if !stdout.ends_with('\n') {
        stdout.push('\n');
    }
    stdout
}

fn add_preamble(generator: &'static str, mut text: String) -> String {
    let preamble = format!("//! Generated by `{generator}`, do not edit by hand.\n\n");
    text.insert_str(0, &preamble);
    text
}

/// Checks that the `file` has the specified `contents`. If that is not the
/// case, updates the file and then fails the test.
#[allow(clippy::print_stderr)]
fn ensure_file_contents(file: &Path, contents: &str, check: bool) {
    if let Ok(old_contents) = fs::read_to_string(file) {
        if normalize_newlines(&old_contents) == normalize_newlines(contents) {
            // File is already up to date.
            return;
        }
    }

    let display_path = file.strip_prefix(project_root()).unwrap_or(file);
    if check {
        panic!(
            "{} was not up-to-date{}",
            file.display(),
            if std::env::var("CI").is_ok() {
                "\n    NOTE: run `cargo codegen` locally and commit the updated files\n"
            } else {
                ""
            }
        );
    } else {
        eprintln!(
            "\n\x1b[31;1merror\x1b[0m: {} was not up-to-date, updating\n",
            display_path.display()
        );

        if let Some(parent) = file.parent() {
            let _ = fs::create_dir_all(parent);
        }
        fs::write(file, contents).unwrap();
    }
}

fn normalize_newlines(s: &str) -> String {
    s.replace("\r\n", "\n")
}