// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

//! Lint engine.
//!
//! The overall design is generally inspired by
//! [Arcanist](https://secure.phabricator.com/book/phabricator/article/arcanist_lint)'s lint engine.

pub mod content;
pub mod file_path;
pub mod package;
pub mod project;
pub mod runner;

use camino::Utf8Path;
use guppy::PackageId;
use std::{borrow::Cow, fmt};

/// Represents a linter.
pub trait Linter: Send + Sync + fmt::Debug {
    /// Returns the name of the linter.
    fn name(&self) -> &'static str;
}

/// Represents common functionality among various `Context` instances.
trait LintContext<'l> {
    /// Returns the kind of this lint context.
    fn kind(&self) -> LintKind<'l>;

    /// Returns a `LintSource` for this lint context.
    fn source(&self, name: &'static str) -> LintSource<'l> {
        LintSource::new(name, self.kind())
    }
}

/// A lint formatter.
///
/// Lints write `LintMessage` instances to this.
pub struct LintFormatter<'l, 'a> {
    source: LintSource<'l>,
    messages: &'a mut Vec<(LintSource<'l>, LintMessage)>,
}

impl<'l, 'a> LintFormatter<'l, 'a> {
    pub fn new(
        source: LintSource<'l>,
        messages: &'a mut Vec<(LintSource<'l>, LintMessage)>,
    ) -> Self {
        Self { source, messages }
    }

    /// Writes a new lint message to this formatter.
    pub fn write(&mut self, level: LintLevel, message: impl Into<Cow<'static, str>>) {
        self.messages
            .push((self.source, LintMessage::new(level, message)));
    }

    /// Writes a new lint message to this formatter with a custom kind.
    pub fn write_kind(
        &mut self,
        kind: LintKind<'l>,
        level: LintLevel,
        message: impl Into<Cow<'static, str>>,
    ) {
        self.messages.push((
            LintSource::new(self.source.name(), kind),
            LintMessage::new(level, message),
        ));
    }
}

/// The run status of a lint.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum RunStatus<'l> {
    /// This lint run was successful, with messages possibly written into the `LintFormatter`.
    Executed,
    /// This lint was skipped.
    Skipped(SkipReason<'l>),
}

/// The reason for why this lint was skipped.
#[derive(Clone, Debug, Eq, PartialEq)]
#[non_exhaustive]
pub enum SkipReason<'l> {
    /// This file's content was not valid UTF-8.
    NonUtf8Content,
    /// This extension was unsupported.
    UnsupportedExtension(Option<&'l str>),
    /// The given file was unsupported by this linter.
    UnsupportedFile(&'l Utf8Path),
    /// The given package was unsupported by this linter.
    UnsupportedPackage(&'l PackageId),
    /// The given file was excepted by a glob rule
    GlobExemption(&'l str),
    // TODO: Add more reasons.
}

/// A message raised by a lint.
#[derive(Debug)]
pub struct LintMessage {
    level: LintLevel,
    message: Cow<'static, str>,
}

impl LintMessage {
    pub fn new(level: LintLevel, message: impl Into<Cow<'static, str>>) -> Self {
        Self {
            level,
            message: message.into(),
        }
    }

    pub fn level(&self) -> LintLevel {
        self.level
    }

    pub fn message(&self) -> &str {
        &self.message
    }
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
#[allow(dead_code)]
#[non_exhaustive]
pub enum LintLevel {
    Error,
    Warning,
    // TODO: add more levels?
}

impl fmt::Display for LintLevel {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            LintLevel::Error => write!(f, "ERROR"),
            LintLevel::Warning => write!(f, "WARNING"),
        }
    }
}

/// Message source for lints.
#[derive(Copy, Clone, Debug)]
pub struct LintSource<'l> {
    name: &'static str,
    kind: LintKind<'l>,
}

impl<'l> LintSource<'l> {
    fn new(name: &'static str, kind: LintKind<'l>) -> Self {
        Self { name, kind }
    }

    pub fn name(&self) -> &'static str {
        self.name
    }

    pub fn kind(&self) -> LintKind<'l> {
        self.kind
    }
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum LintKind<'l> {
    Project,
    Package {
        name: &'l str,
        workspace_path: &'l Utf8Path,
    },
    FilePath(&'l Utf8Path),
    Content(&'l Utf8Path),
}

impl<'l> fmt::Display for LintKind<'l> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            LintKind::Project => write!(f, "project"),
            LintKind::Package {
                name,
                workspace_path,
            } => write!(f, "package '{}' (at {})", name, workspace_path),
            LintKind::FilePath(path) => write!(f, "file path {}", path),
            LintKind::Content(path) => write!(f, "content {}", path),
        }
    }
}

pub mod prelude {
    pub use super::{
        content::{ContentContext, ContentLinter},
        file_path::{FilePathContext, FilePathLinter},
        package::{PackageContext, PackageLinter},
        project::{ProjectContext, ProjectLinter},
        runner::{LintEngine, LintEngineConfig, LintResults},
        LintFormatter, LintKind, LintLevel, LintMessage, LintSource, Linter, RunStatus, SkipReason,
    };
    pub use x_core::{Result, SystemError};
}