//! lint on enum variants that are prefixed or suffixed by the same characters

use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_hir};
use clippy_utils::macros::span_is_local;
use clippy_utils::source::is_present_in_source;
use clippy_utils::str_utils::{camel_case_split, count_match_end, count_match_start, to_camel_case, to_snake_case};
use rustc_hir::{EnumDef, FieldDef, Item, ItemKind, OwnerId, Variant, VariantData};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::symbol::Symbol;
use rustc_span::Span;

declare_clippy_lint! {
    /// ### What it does
    /// Detects enumeration variants that are prefixed or suffixed
    /// by the same characters.
    ///
    /// ### Why is this bad?
    /// Enumeration variant names should specify their variant,
    /// not repeat the enumeration name.
    ///
    /// ### Limitations
    /// Characters with no casing will be considered when comparing prefixes/suffixes
    /// This applies to numbers and non-ascii characters without casing
    /// e.g. `Foo1` and `Foo2` is considered to have different prefixes
    /// (the prefixes are `Foo1` and `Foo2` respectively), as also `Bar螃`, `Bar蟹`
    ///
    /// ### Example
    /// ```no_run
    /// enum Cake {
    ///     BlackForestCake,
    ///     HummingbirdCake,
    ///     BattenbergCake,
    /// }
    /// ```
    /// Use instead:
    /// ```no_run
    /// enum Cake {
    ///     BlackForest,
    ///     Hummingbird,
    ///     Battenberg,
    /// }
    /// ```
    #[clippy::version = "pre 1.29.0"]
    pub ENUM_VARIANT_NAMES,
    style,
    "enums where all variants share a prefix/postfix"
}

declare_clippy_lint! {
    /// ### What it does
    /// Detects type names that are prefixed or suffixed by the
    /// containing module's name.
    ///
    /// ### Why is this bad?
    /// It requires the user to type the module name twice.
    ///
    /// ### Example
    /// ```no_run
    /// mod cake {
    ///     struct BlackForestCake;
    /// }
    /// ```
    ///
    /// Use instead:
    /// ```no_run
    /// mod cake {
    ///     struct BlackForest;
    /// }
    /// ```
    #[clippy::version = "1.33.0"]
    pub MODULE_NAME_REPETITIONS,
    pedantic,
    "type names prefixed/postfixed with their containing module's name"
}

declare_clippy_lint! {
    /// ### What it does
    /// Checks for modules that have the same name as their
    /// parent module
    ///
    /// ### Why is this bad?
    /// A typical beginner mistake is to have `mod foo;` and
    /// again `mod foo { ..
    /// }` in `foo.rs`.
    /// The expectation is that items inside the inner `mod foo { .. }` are then
    /// available
    /// through `foo::x`, but they are only available through
    /// `foo::foo::x`.
    /// If this is done on purpose, it would be better to choose a more
    /// representative module name.
    ///
    /// ### Example
    /// ```ignore
    /// // lib.rs
    /// mod foo;
    /// // foo.rs
    /// mod foo {
    ///     ...
    /// }
    /// ```
    #[clippy::version = "pre 1.29.0"]
    pub MODULE_INCEPTION,
    style,
    "modules that have the same name as their parent module"
}
declare_clippy_lint! {
    /// ### What it does
    /// Detects struct fields that are prefixed or suffixed
    /// by the same characters or the name of the struct itself.
    ///
    /// ### Why is this bad?
    /// Information common to all struct fields is better represented in the struct name.
    ///
    /// ### Limitations
    /// Characters with no casing will be considered when comparing prefixes/suffixes
    /// This applies to numbers and non-ascii characters without casing
    /// e.g. `foo1` and `foo2` is considered to have different prefixes
    /// (the prefixes are `foo1` and `foo2` respectively), as also `bar螃`, `bar蟹`
    ///
    /// ### Example
    /// ```no_run
    /// struct Cake {
    ///     cake_sugar: u8,
    ///     cake_flour: u8,
    ///     cake_eggs: u8
    /// }
    /// ```
    /// Use instead:
    /// ```no_run
    /// struct Cake {
    ///     sugar: u8,
    ///     flour: u8,
    ///     eggs: u8
    /// }
    /// ```
    #[clippy::version = "1.75.0"]
    pub STRUCT_FIELD_NAMES,
    pedantic,
    "structs where all fields share a prefix/postfix or contain the name of the struct"
}

pub struct ItemNameRepetitions {
    modules: Vec<(Symbol, String, OwnerId)>,
    enum_threshold: u64,
    struct_threshold: u64,
    avoid_breaking_exported_api: bool,
    allow_private_module_inception: bool,
}

impl ItemNameRepetitions {
    #[must_use]
    pub fn new(
        enum_threshold: u64,
        struct_threshold: u64,
        avoid_breaking_exported_api: bool,
        allow_private_module_inception: bool,
    ) -> Self {
        Self {
            modules: Vec::new(),
            enum_threshold,
            struct_threshold,
            avoid_breaking_exported_api,
            allow_private_module_inception,
        }
    }
}

impl_lint_pass!(ItemNameRepetitions => [
    ENUM_VARIANT_NAMES,
    STRUCT_FIELD_NAMES,
    MODULE_NAME_REPETITIONS,
    MODULE_INCEPTION
]);

#[must_use]
fn have_no_extra_prefix(prefixes: &[&str]) -> bool {
    prefixes.iter().all(|p| p == &"" || p == &"_")
}

fn check_fields(cx: &LateContext<'_>, threshold: u64, item: &Item<'_>, fields: &[FieldDef<'_>]) {
    if (fields.len() as u64) < threshold {
        return;
    }

    check_struct_name_repetition(cx, item, fields);

    // if the SyntaxContext of the identifiers of the fields and struct differ dont lint them.
    // this prevents linting in macros in which the location of the field identifier names differ
    if !fields.iter().all(|field| item.ident.span.eq_ctxt(field.ident.span)) {
        return;
    }

    let mut pre: Vec<&str> = match fields.first() {
        Some(first_field) => first_field.ident.name.as_str().split('_').collect(),
        None => return,
    };
    let mut post = pre.clone();
    post.reverse();
    for field in fields {
        let field_split: Vec<&str> = field.ident.name.as_str().split('_').collect();
        if field_split.len() == 1 {
            return;
        }

        pre = pre
            .into_iter()
            .zip(field_split.iter())
            .take_while(|(a, b)| &a == b)
            .map(|e| e.0)
            .collect();
        post = post
            .into_iter()
            .zip(field_split.iter().rev())
            .take_while(|(a, b)| &a == b)
            .map(|e| e.0)
            .collect();
    }
    let prefix = pre.join("_");
    post.reverse();
    let postfix = match post.last() {
        Some(&"") => post.join("_") + "_",
        Some(_) | None => post.join("_"),
    };
    if fields.len() > 1 {
        let (what, value) = match (
            prefix.is_empty() || prefix.chars().all(|c| c == '_'),
            postfix.is_empty(),
        ) {
            (true, true) => return,
            (false, _) => ("pre", prefix),
            (true, false) => ("post", postfix),
        };
        span_lint_and_help(
            cx,
            STRUCT_FIELD_NAMES,
            item.span,
            &format!("all fields have the same {what}fix: `{value}`"),
            None,
            &format!("remove the {what}fixes"),
        );
    }
}

fn check_struct_name_repetition(cx: &LateContext<'_>, item: &Item<'_>, fields: &[FieldDef<'_>]) {
    let snake_name = to_snake_case(item.ident.name.as_str());
    let item_name_words: Vec<&str> = snake_name.split('_').collect();
    for field in fields {
        if field.ident.span.eq_ctxt(item.ident.span) {
            //consider linting only if the field identifier has the same SyntaxContext as the item(struct)
            let field_words: Vec<&str> = field.ident.name.as_str().split('_').collect();
            if field_words.len() >= item_name_words.len() {
                // if the field name is shorter than the struct name it cannot contain it
                if field_words.iter().zip(item_name_words.iter()).all(|(a, b)| a == b) {
                    span_lint_hir(
                        cx,
                        STRUCT_FIELD_NAMES,
                        field.hir_id,
                        field.span,
                        "field name starts with the struct's name",
                    );
                }
                if field_words.len() > item_name_words.len() {
                    // lint only if the end is not covered by the start
                    if field_words
                        .iter()
                        .rev()
                        .zip(item_name_words.iter().rev())
                        .all(|(a, b)| a == b)
                    {
                        span_lint_hir(
                            cx,
                            STRUCT_FIELD_NAMES,
                            field.hir_id,
                            field.span,
                            "field name ends with the struct's name",
                        );
                    }
                }
            }
        }
    }
}

fn check_enum_start(cx: &LateContext<'_>, item_name: &str, variant: &Variant<'_>) {
    let name = variant.ident.name.as_str();
    let item_name_chars = item_name.chars().count();

    if count_match_start(item_name, name).char_count == item_name_chars
        && name.chars().nth(item_name_chars).map_or(false, |c| !c.is_lowercase())
        && name.chars().nth(item_name_chars + 1).map_or(false, |c| !c.is_numeric())
    {
        span_lint_hir(
            cx,
            ENUM_VARIANT_NAMES,
            variant.hir_id,
            variant.span,
            "variant name starts with the enum's name",
        );
    }
}

fn check_enum_end(cx: &LateContext<'_>, item_name: &str, variant: &Variant<'_>) {
    let name = variant.ident.name.as_str();
    let item_name_chars = item_name.chars().count();

    if count_match_end(item_name, name).char_count == item_name_chars {
        span_lint_hir(
            cx,
            ENUM_VARIANT_NAMES,
            variant.hir_id,
            variant.span,
            "variant name ends with the enum's name",
        );
    }
}

fn check_variant(cx: &LateContext<'_>, threshold: u64, def: &EnumDef<'_>, item_name: &str, span: Span) {
    if (def.variants.len() as u64) < threshold {
        return;
    }

    for var in def.variants {
        check_enum_start(cx, item_name, var);
        check_enum_end(cx, item_name, var);
    }

    let first = match def.variants.first() {
        Some(variant) => variant.ident.name.as_str(),
        None => return,
    };
    let mut pre = camel_case_split(first);
    let mut post = pre.clone();
    post.reverse();
    for var in def.variants {
        let name = var.ident.name.as_str();

        let variant_split = camel_case_split(name);
        if variant_split.len() == 1 {
            return;
        }

        pre = pre
            .iter()
            .zip(variant_split.iter())
            .take_while(|(a, b)| a == b)
            .map(|e| *e.0)
            .collect();
        post = post
            .iter()
            .zip(variant_split.iter().rev())
            .take_while(|(a, b)| a == b)
            .map(|e| *e.0)
            .collect();
    }
    let (what, value) = match (have_no_extra_prefix(&pre), post.is_empty()) {
        (true, true) => return,
        (false, _) => ("pre", pre.join("")),
        (true, false) => {
            post.reverse();
            ("post", post.join(""))
        },
    };
    span_lint_and_help(
        cx,
        ENUM_VARIANT_NAMES,
        span,
        &format!("all variants have the same {what}fix: `{value}`"),
        None,
        &format!(
            "remove the {what}fixes and use full paths to \
             the variants instead of glob imports"
        ),
    );
}

impl LateLintPass<'_> for ItemNameRepetitions {
    fn check_item_post(&mut self, _cx: &LateContext<'_>, _item: &Item<'_>) {
        let last = self.modules.pop();
        assert!(last.is_some());
    }

    #[expect(clippy::similar_names)]
    fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
        let item_name = item.ident.name.as_str();
        let item_camel = to_camel_case(item_name);
        if !item.span.from_expansion() && is_present_in_source(cx, item.span) {
            if let [.., (mod_name, mod_camel, owner_id)] = &*self.modules {
                // constants don't have surrounding modules
                if !mod_camel.is_empty() {
                    if mod_name == &item.ident.name
                        && let ItemKind::Mod(..) = item.kind
                        && (!self.allow_private_module_inception || cx.tcx.visibility(owner_id.def_id).is_public())
                    {
                        span_lint(
                            cx,
                            MODULE_INCEPTION,
                            item.span,
                            "module has the same name as its containing module",
                        );
                    }
                    // The `module_name_repetitions` lint should only trigger if the item has the module in its
                    // name. Having the same name is accepted.
                    if cx.tcx.visibility(item.owner_id).is_public() && item_camel.len() > mod_camel.len() {
                        let matching = count_match_start(mod_camel, &item_camel);
                        let rmatching = count_match_end(mod_camel, &item_camel);
                        let nchars = mod_camel.chars().count();

                        let is_word_beginning = |c: char| c == '_' || c.is_uppercase() || c.is_numeric();

                        if matching.char_count == nchars {
                            match item_camel.chars().nth(nchars) {
                                Some(c) if is_word_beginning(c) => span_lint(
                                    cx,
                                    MODULE_NAME_REPETITIONS,
                                    item.ident.span,
                                    "item name starts with its containing module's name",
                                ),
                                _ => (),
                            }
                        }
                        if rmatching.char_count == nchars {
                            span_lint(
                                cx,
                                MODULE_NAME_REPETITIONS,
                                item.ident.span,
                                "item name ends with its containing module's name",
                            );
                        }
                    }
                }
            }
        }
        if !(self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(item.owner_id.def_id))
            && span_is_local(item.span)
        {
            match item.kind {
                ItemKind::Enum(def, _) => check_variant(cx, self.enum_threshold, &def, item_name, item.span),
                ItemKind::Struct(VariantData::Struct(fields, _), _) => {
                    check_fields(cx, self.struct_threshold, item, fields);
                },
                _ => (),
            }
        }
        self.modules.push((item.ident.name, item_camel, item.owner_id));
    }
}