use crate::core::dependency::DepKind;
use crate::core::FeatureValue::Dep;
use crate::core::{Edition, Feature, FeatureValue, Features, Manifest, Package};
use crate::util::interning::InternedString;
use crate::{CargoResult, GlobalContext};
use annotate_snippets::{Level, Snippet};
use cargo_util_schemas::manifest::{TomlLintLevel, TomlToolLints};
use pathdiff::diff_paths;
use std::collections::HashSet;
use std::fmt::Display;
use std::ops::Range;
use std::path::Path;
use toml_edit::ImDocument;

const LINT_GROUPS: &[LintGroup] = &[TEST_DUMMY_UNSTABLE];
const LINTS: &[Lint] = &[IM_A_TEAPOT, IMPLICIT_FEATURES, UNUSED_OPTIONAL_DEPENDENCY];

pub fn analyze_cargo_lints_table(
    pkg: &Package,
    path: &Path,
    pkg_lints: &TomlToolLints,
    ws_contents: &str,
    ws_document: &ImDocument<String>,
    ws_path: &Path,
    gctx: &GlobalContext,
) -> CargoResult<()> {
    let mut error_count = 0;
    let manifest = pkg.manifest();
    let manifest_path = rel_cwd_manifest_path(path, gctx);
    let ws_path = rel_cwd_manifest_path(ws_path, gctx);
    let mut unknown_lints = Vec::new();
    for lint_name in pkg_lints.keys().map(|name| name) {
        let Some((name, default_level, edition_lint_opts, feature_gate)) =
            find_lint_or_group(lint_name)
        else {
            unknown_lints.push(lint_name);
            continue;
        };

        let (_, reason, _) = level_priority(
            name,
            *default_level,
            *edition_lint_opts,
            pkg_lints,
            manifest.edition(),
        );

        // Only run analysis on user-specified lints
        if !reason.is_user_specified() {
            continue;
        }

        // Only run this on lints that are gated by a feature
        if let Some(feature_gate) = feature_gate {
            verify_feature_enabled(
                name,
                feature_gate,
                manifest,
                &manifest_path,
                ws_contents,
                ws_document,
                &ws_path,
                &mut error_count,
                gctx,
            )?;
        }
    }

    output_unknown_lints(
        unknown_lints,
        manifest,
        &manifest_path,
        pkg_lints,
        ws_contents,
        ws_document,
        &ws_path,
        &mut error_count,
        gctx,
    )?;

    if error_count > 0 {
        Err(anyhow::anyhow!(
            "encountered {error_count} errors(s) while verifying lints",
        ))
    } else {
        Ok(())
    }
}

fn find_lint_or_group<'a>(
    name: &str,
) -> Option<(
    &'static str,
    &LintLevel,
    &Option<(Edition, LintLevel)>,
    &Option<&'static Feature>,
)> {
    if let Some(lint) = LINTS.iter().find(|l| l.name == name) {
        Some((
            lint.name,
            &lint.default_level,
            &lint.edition_lint_opts,
            &lint.feature_gate,
        ))
    } else if let Some(group) = LINT_GROUPS.iter().find(|g| g.name == name) {
        Some((
            group.name,
            &group.default_level,
            &group.edition_lint_opts,
            &group.feature_gate,
        ))
    } else {
        None
    }
}

fn verify_feature_enabled(
    lint_name: &str,
    feature_gate: &Feature,
    manifest: &Manifest,
    manifest_path: &str,
    ws_contents: &str,
    ws_document: &ImDocument<String>,
    ws_path: &str,
    error_count: &mut usize,
    gctx: &GlobalContext,
) -> CargoResult<()> {
    if !manifest.unstable_features().is_enabled(feature_gate) {
        let dash_feature_name = feature_gate.name().replace("_", "-");
        let title = format!("use of unstable lint `{}`", lint_name);
        let label = format!(
            "this is behind `{}`, which is not enabled",
            dash_feature_name
        );
        let second_title = format!("`cargo::{}` was inherited", lint_name);
        let help = format!(
            "consider adding `cargo-features = [\"{}\"]` to the top of the manifest",
            dash_feature_name
        );

        let message = if let Some(span) =
            get_span(manifest.document(), &["lints", "cargo", lint_name], false)
        {
            Level::Error
                .title(&title)
                .snippet(
                    Snippet::source(manifest.contents())
                        .origin(&manifest_path)
                        .annotation(Level::Error.span(span).label(&label))
                        .fold(true),
                )
                .footer(Level::Help.title(&help))
        } else {
            let lint_span = get_span(
                ws_document,
                &["workspace", "lints", "cargo", lint_name],
                false,
            )
            .expect(&format!(
                "could not find `cargo::{lint_name}` in `[lints]`, or `[workspace.lints]` "
            ));

            let inherited_note = if let (Some(inherit_span_key), Some(inherit_span_value)) = (
                get_span(manifest.document(), &["lints", "workspace"], false),
                get_span(manifest.document(), &["lints", "workspace"], true),
            ) {
                Level::Note.title(&second_title).snippet(
                    Snippet::source(manifest.contents())
                        .origin(&manifest_path)
                        .annotation(
                            Level::Note.span(inherit_span_key.start..inherit_span_value.end),
                        )
                        .fold(true),
                )
            } else {
                Level::Note.title(&second_title)
            };

            Level::Error
                .title(&title)
                .snippet(
                    Snippet::source(ws_contents)
                        .origin(&ws_path)
                        .annotation(Level::Error.span(lint_span).label(&label))
                        .fold(true),
                )
                .footer(inherited_note)
                .footer(Level::Help.title(&help))
        };

        *error_count += 1;
        gctx.shell().print_message(message)?;
    }
    Ok(())
}

fn get_span(document: &ImDocument<String>, path: &[&str], get_value: bool) -> Option<Range<usize>> {
    let mut table = document.as_item().as_table_like()?;
    let mut iter = path.into_iter().peekable();
    while let Some(key) = iter.next() {
        let (key, item) = table.get_key_value(key)?;
        if iter.peek().is_none() {
            return if get_value {
                item.span()
            } else {
                let leaf_decor = key.dotted_decor();
                let leaf_prefix_span = leaf_decor.prefix().and_then(|p| p.span());
                let leaf_suffix_span = leaf_decor.suffix().and_then(|s| s.span());
                if let (Some(leaf_prefix_span), Some(leaf_suffix_span)) =
                    (leaf_prefix_span, leaf_suffix_span)
                {
                    Some(leaf_prefix_span.start..leaf_suffix_span.end)
                } else {
                    key.span()
                }
            };
        }
        if item.is_table_like() {
            table = item.as_table_like().unwrap();
        }
        if item.is_array() && iter.peek().is_some() {
            let array = item.as_array().unwrap();
            let next = iter.next().unwrap();
            return array.iter().find_map(|item| {
                if next == &item.to_string() {
                    item.span()
                } else {
                    None
                }
            });
        }
    }
    None
}

/// Gets the relative path to a manifest from the current working directory, or
/// the absolute path of the manifest if a relative path cannot be constructed
fn rel_cwd_manifest_path(path: &Path, gctx: &GlobalContext) -> String {
    diff_paths(path, gctx.cwd())
        .unwrap_or_else(|| path.to_path_buf())
        .display()
        .to_string()
}

#[derive(Copy, Clone, Debug)]
pub struct LintGroup {
    pub name: &'static str,
    pub default_level: LintLevel,
    pub desc: &'static str,
    pub edition_lint_opts: Option<(Edition, LintLevel)>,
    pub feature_gate: Option<&'static Feature>,
}

const TEST_DUMMY_UNSTABLE: LintGroup = LintGroup {
    name: "test_dummy_unstable",
    desc: "test_dummy_unstable is meant to only be used in tests",
    default_level: LintLevel::Allow,
    edition_lint_opts: None,
    feature_gate: Some(Feature::test_dummy_unstable()),
};

#[derive(Copy, Clone, Debug)]
pub struct Lint {
    pub name: &'static str,
    pub desc: &'static str,
    pub groups: &'static [LintGroup],
    pub default_level: LintLevel,
    pub edition_lint_opts: Option<(Edition, LintLevel)>,
    pub feature_gate: Option<&'static Feature>,
}

impl Lint {
    pub fn level(
        &self,
        pkg_lints: &TomlToolLints,
        edition: Edition,
        unstable_features: &Features,
    ) -> (LintLevel, LintLevelReason) {
        // We should return `Allow` if a lint is behind a feature, but it is
        // not enabled, that way the lint does not run.
        if self
            .feature_gate
            .is_some_and(|f| !unstable_features.is_enabled(f))
        {
            return (LintLevel::Allow, LintLevelReason::Default);
        }

        self.groups
            .iter()
            .map(|g| {
                (
                    g.name,
                    level_priority(
                        g.name,
                        g.default_level,
                        g.edition_lint_opts,
                        pkg_lints,
                        edition,
                    ),
                )
            })
            .chain(std::iter::once((
                self.name,
                level_priority(
                    self.name,
                    self.default_level,
                    self.edition_lint_opts,
                    pkg_lints,
                    edition,
                ),
            )))
            .max_by_key(|(n, (l, _, p))| (l == &LintLevel::Forbid, *p, std::cmp::Reverse(*n)))
            .map(|(_, (l, r, _))| (l, r))
            .unwrap()
    }
}

#[derive(Copy, Clone, Debug, PartialEq)]
pub enum LintLevel {
    Allow,
    Warn,
    Deny,
    Forbid,
}

impl Display for LintLevel {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            LintLevel::Allow => write!(f, "allow"),
            LintLevel::Warn => write!(f, "warn"),
            LintLevel::Deny => write!(f, "deny"),
            LintLevel::Forbid => write!(f, "forbid"),
        }
    }
}

impl LintLevel {
    pub fn to_diagnostic_level(self) -> Level {
        match self {
            LintLevel::Allow => unreachable!("allow does not map to a diagnostic level"),
            LintLevel::Warn => Level::Warning,
            LintLevel::Deny => Level::Error,
            LintLevel::Forbid => Level::Error,
        }
    }
}

impl From<TomlLintLevel> for LintLevel {
    fn from(toml_lint_level: TomlLintLevel) -> LintLevel {
        match toml_lint_level {
            TomlLintLevel::Allow => LintLevel::Allow,
            TomlLintLevel::Warn => LintLevel::Warn,
            TomlLintLevel::Deny => LintLevel::Deny,
            TomlLintLevel::Forbid => LintLevel::Forbid,
        }
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum LintLevelReason {
    Default,
    Edition(Edition),
    Package,
}

impl Display for LintLevelReason {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            LintLevelReason::Default => write!(f, "by default"),
            LintLevelReason::Edition(edition) => write!(f, "in edition {}", edition),
            LintLevelReason::Package => write!(f, "in `[lints]`"),
        }
    }
}

impl LintLevelReason {
    fn is_user_specified(&self) -> bool {
        match self {
            LintLevelReason::Default => false,
            LintLevelReason::Edition(_) => false,
            LintLevelReason::Package => true,
        }
    }
}

fn level_priority(
    name: &str,
    default_level: LintLevel,
    edition_lint_opts: Option<(Edition, LintLevel)>,
    pkg_lints: &TomlToolLints,
    edition: Edition,
) -> (LintLevel, LintLevelReason, i8) {
    let (unspecified_level, reason) = if let Some(level) = edition_lint_opts
        .filter(|(e, _)| edition >= *e)
        .map(|(_, l)| l)
    {
        (level, LintLevelReason::Edition(edition))
    } else {
        (default_level, LintLevelReason::Default)
    };

    // Don't allow the group to be overridden if the level is `Forbid`
    if unspecified_level == LintLevel::Forbid {
        return (unspecified_level, reason, 0);
    }

    if let Some(defined_level) = pkg_lints.get(name) {
        (
            defined_level.level().into(),
            LintLevelReason::Package,
            defined_level.priority(),
        )
    } else {
        (unspecified_level, reason, 0)
    }
}

const IM_A_TEAPOT: Lint = Lint {
    name: "im_a_teapot",
    desc: "`im_a_teapot` is specified",
    groups: &[TEST_DUMMY_UNSTABLE],
    default_level: LintLevel::Allow,
    edition_lint_opts: None,
    feature_gate: Some(Feature::test_dummy_unstable()),
};

pub fn check_im_a_teapot(
    pkg: &Package,
    path: &Path,
    pkg_lints: &TomlToolLints,
    error_count: &mut usize,
    gctx: &GlobalContext,
) -> CargoResult<()> {
    let manifest = pkg.manifest();
    let (lint_level, reason) =
        IM_A_TEAPOT.level(pkg_lints, manifest.edition(), manifest.unstable_features());

    if lint_level == LintLevel::Allow {
        return Ok(());
    }

    if manifest
        .resolved_toml()
        .package()
        .is_some_and(|p| p.im_a_teapot.is_some())
    {
        if lint_level == LintLevel::Forbid || lint_level == LintLevel::Deny {
            *error_count += 1;
        }
        let level = lint_level.to_diagnostic_level();
        let manifest_path = rel_cwd_manifest_path(path, gctx);
        let emitted_reason = format!(
            "`cargo::{}` is set to `{lint_level}` {reason}",
            IM_A_TEAPOT.name
        );

        let key_span = get_span(manifest.document(), &["package", "im-a-teapot"], false).unwrap();
        let value_span = get_span(manifest.document(), &["package", "im-a-teapot"], true).unwrap();
        let message = level
            .title(IM_A_TEAPOT.desc)
            .snippet(
                Snippet::source(manifest.contents())
                    .origin(&manifest_path)
                    .annotation(level.span(key_span.start..value_span.end))
                    .fold(true),
            )
            .footer(Level::Note.title(&emitted_reason));

        gctx.shell().print_message(message)?;
    }
    Ok(())
}

/// By default, cargo will treat any optional dependency as a [feature]. As of
/// cargo 1.60, these can be disabled by declaring a feature that activates the
/// optional dependency as `dep:<name>` (see [RFC #3143]).
///
/// In the 2024 edition, `cargo` will stop exposing optional dependencies as
/// features implicitly, requiring users to add `foo = ["dep:foo"]` if they
/// still want it exposed.
///
/// For more information, see [RFC #3491]
///
/// [feature]: https://doc.rust-lang.org/cargo/reference/features.html
/// [RFC #3143]: https://rust-lang.github.io/rfcs/3143-cargo-weak-namespaced-features.html
/// [RFC #3491]: https://rust-lang.github.io/rfcs/3491-remove-implicit-features.html
const IMPLICIT_FEATURES: Lint = Lint {
    name: "implicit_features",
    desc: "implicit features for optional dependencies is deprecated and will be unavailable in the 2024 edition",
    groups: &[],
    default_level: LintLevel::Allow,
    edition_lint_opts: None,
    feature_gate: None,
};

pub fn check_implicit_features(
    pkg: &Package,
    path: &Path,
    pkg_lints: &TomlToolLints,
    error_count: &mut usize,
    gctx: &GlobalContext,
) -> CargoResult<()> {
    let manifest = pkg.manifest();
    let edition = manifest.edition();
    // In Edition 2024+, instead of creating optional features, the dependencies are unused.
    // See `UNUSED_OPTIONAL_DEPENDENCY`
    if edition >= Edition::Edition2024 {
        return Ok(());
    }

    let (lint_level, reason) =
        IMPLICIT_FEATURES.level(pkg_lints, edition, manifest.unstable_features());
    if lint_level == LintLevel::Allow {
        return Ok(());
    }

    let activated_opt_deps = manifest
        .resolved_toml()
        .features()
        .map(|map| {
            map.values()
                .flatten()
                .filter_map(|f| match FeatureValue::new(InternedString::new(f)) {
                    Dep { dep_name } => Some(dep_name.as_str()),
                    _ => None,
                })
                .collect::<HashSet<_>>()
        })
        .unwrap_or_default();

    let mut emitted_source = None;
    for dep in manifest.dependencies() {
        let dep_name_in_toml = dep.name_in_toml();
        if !dep.is_optional() || activated_opt_deps.contains(dep_name_in_toml.as_str()) {
            continue;
        }
        if lint_level == LintLevel::Forbid || lint_level == LintLevel::Deny {
            *error_count += 1;
        }
        let mut toml_path = vec![dep.kind().kind_table(), dep_name_in_toml.as_str()];
        let platform = dep.platform().map(|p| p.to_string());
        if let Some(platform) = platform.as_ref() {
            toml_path.insert(0, platform);
            toml_path.insert(0, "target");
        }
        let level = lint_level.to_diagnostic_level();
        let manifest_path = rel_cwd_manifest_path(path, gctx);
        let mut message = level.title(IMPLICIT_FEATURES.desc).snippet(
            Snippet::source(manifest.contents())
                .origin(&manifest_path)
                .annotation(level.span(get_span(manifest.document(), &toml_path, false).unwrap()))
                .fold(true),
        );
        if emitted_source.is_none() {
            emitted_source = Some(format!(
                "`cargo::{}` is set to `{lint_level}` {reason}",
                IMPLICIT_FEATURES.name
            ));
            message = message.footer(Level::Note.title(emitted_source.as_ref().unwrap()));
        }
        gctx.shell().print_message(message)?;
    }
    Ok(())
}

const UNKNOWN_LINTS: Lint = Lint {
    name: "unknown_lints",
    desc: "unknown lint",
    groups: &[],
    default_level: LintLevel::Warn,
    edition_lint_opts: None,
    feature_gate: None,
};

fn output_unknown_lints(
    unknown_lints: Vec<&String>,
    manifest: &Manifest,
    manifest_path: &str,
    pkg_lints: &TomlToolLints,
    ws_contents: &str,
    ws_document: &ImDocument<String>,
    ws_path: &str,
    error_count: &mut usize,
    gctx: &GlobalContext,
) -> CargoResult<()> {
    let (lint_level, reason) =
        UNKNOWN_LINTS.level(pkg_lints, manifest.edition(), manifest.unstable_features());
    if lint_level == LintLevel::Allow {
        return Ok(());
    }

    let level = lint_level.to_diagnostic_level();
    let mut emitted_source = None;
    for lint_name in unknown_lints {
        if lint_level == LintLevel::Forbid || lint_level == LintLevel::Deny {
            *error_count += 1;
        }
        let title = format!("{}: `{lint_name}`", UNKNOWN_LINTS.desc);
        let second_title = format!("`cargo::{}` was inherited", lint_name);
        let underscore_lint_name = lint_name.replace("-", "_");
        let matching = if let Some(lint) = LINTS.iter().find(|l| l.name == underscore_lint_name) {
            Some((lint.name, "lint"))
        } else if let Some(group) = LINT_GROUPS.iter().find(|g| g.name == underscore_lint_name) {
            Some((group.name, "group"))
        } else {
            None
        };
        let help =
            matching.map(|(name, kind)| format!("there is a {kind} with a similar name: `{name}`"));

        let mut message = if let Some(span) =
            get_span(manifest.document(), &["lints", "cargo", lint_name], false)
        {
            level.title(&title).snippet(
                Snippet::source(manifest.contents())
                    .origin(&manifest_path)
                    .annotation(Level::Error.span(span))
                    .fold(true),
            )
        } else {
            let lint_span = get_span(
                ws_document,
                &["workspace", "lints", "cargo", lint_name],
                false,
            )
            .expect(&format!(
                "could not find `cargo::{lint_name}` in `[lints]`, or `[workspace.lints]` "
            ));

            let inherited_note = if let (Some(inherit_span_key), Some(inherit_span_value)) = (
                get_span(manifest.document(), &["lints", "workspace"], false),
                get_span(manifest.document(), &["lints", "workspace"], true),
            ) {
                Level::Note.title(&second_title).snippet(
                    Snippet::source(manifest.contents())
                        .origin(&manifest_path)
                        .annotation(
                            Level::Note.span(inherit_span_key.start..inherit_span_value.end),
                        )
                        .fold(true),
                )
            } else {
                Level::Note.title(&second_title)
            };

            level
                .title(&title)
                .snippet(
                    Snippet::source(ws_contents)
                        .origin(&ws_path)
                        .annotation(Level::Error.span(lint_span))
                        .fold(true),
                )
                .footer(inherited_note)
        };

        if emitted_source.is_none() {
            emitted_source = Some(format!(
                "`cargo::{}` is set to `{lint_level}` {reason}",
                UNKNOWN_LINTS.name
            ));
            message = message.footer(Level::Note.title(emitted_source.as_ref().unwrap()));
        }

        if let Some(help) = help.as_ref() {
            message = message.footer(Level::Help.title(help));
        }

        gctx.shell().print_message(message)?;
    }

    Ok(())
}

const UNUSED_OPTIONAL_DEPENDENCY: Lint = Lint {
    name: "unused_optional_dependency",
    desc: "unused optional dependency",
    groups: &[],
    default_level: LintLevel::Warn,
    edition_lint_opts: None,
    feature_gate: None,
};

pub fn unused_dependencies(
    pkg: &Package,
    path: &Path,
    pkg_lints: &TomlToolLints,
    error_count: &mut usize,
    gctx: &GlobalContext,
) -> CargoResult<()> {
    let manifest = pkg.manifest();
    let edition = manifest.edition();
    // Unused optional dependencies can only exist on edition 2024+
    if edition < Edition::Edition2024 {
        return Ok(());
    }

    let (lint_level, reason) =
        UNUSED_OPTIONAL_DEPENDENCY.level(pkg_lints, edition, manifest.unstable_features());
    if lint_level == LintLevel::Allow {
        return Ok(());
    }
    let mut emitted_source = None;
    let original_toml = manifest.original_toml();
    // Unused dependencies were stripped from the manifest, leaving only the used ones
    let used_dependencies = manifest
        .dependencies()
        .into_iter()
        .map(|d| d.name_in_toml().to_string())
        .collect::<HashSet<String>>();
    let mut orig_deps = vec![
        (
            original_toml.dependencies.as_ref(),
            vec![DepKind::Normal.kind_table()],
        ),
        (
            original_toml.dev_dependencies.as_ref(),
            vec![DepKind::Development.kind_table()],
        ),
        (
            original_toml.build_dependencies.as_ref(),
            vec![DepKind::Build.kind_table()],
        ),
    ];
    for (name, platform) in original_toml.target.iter().flatten() {
        orig_deps.push((
            platform.dependencies.as_ref(),
            vec!["target", name, DepKind::Normal.kind_table()],
        ));
        orig_deps.push((
            platform.dev_dependencies.as_ref(),
            vec!["target", name, DepKind::Development.kind_table()],
        ));
        orig_deps.push((
            platform.build_dependencies.as_ref(),
            vec!["target", name, DepKind::Normal.kind_table()],
        ));
    }
    for (deps, toml_path) in orig_deps {
        if let Some(deps) = deps {
            for name in deps.keys() {
                if !used_dependencies.contains(name.as_str()) {
                    if lint_level == LintLevel::Forbid || lint_level == LintLevel::Deny {
                        *error_count += 1;
                    }
                    let toml_path = toml_path
                        .iter()
                        .map(|s| *s)
                        .chain(std::iter::once(name.as_str()))
                        .collect::<Vec<_>>();
                    let level = lint_level.to_diagnostic_level();
                    let manifest_path = rel_cwd_manifest_path(path, gctx);

                    let mut message = level.title(UNUSED_OPTIONAL_DEPENDENCY.desc).snippet(
                        Snippet::source(manifest.contents())
                            .origin(&manifest_path)
                            .annotation(level.span(
                                get_span(manifest.document(), toml_path.as_slice(), false).unwrap(),
                            ))
                            .fold(true),
                    );
                    if emitted_source.is_none() {
                        emitted_source = Some(format!(
                            "`cargo::{}` is set to `{lint_level}` {reason}",
                            UNUSED_OPTIONAL_DEPENDENCY.name
                        ));
                        message =
                            message.footer(Level::Note.title(emitted_source.as_ref().unwrap()));
                    }
                    let help = format!(
                        "remove the dependency or activate it in a feature with `dep:{name}`"
                    );
                    message = message.footer(Level::Help.title(&help));

                    gctx.shell().print_message(message)?;
                }
            }
        }
    }
    Ok(())
}