vibe-style 0.1.4

use std::collections::BTreeMap;

use ra_ap_syntax::{
	AstNode, SyntaxKind,
	ast::{
		self, GenericArg, GenericParam, HasGenericArgs, HasGenericParams, HasName, HasVisibility,
		Path, PathSegment, Type, TypeAlias, Use,
	},
};

use crate::style::shared::{self, Edit, FileContext, Violation};

const RULE_ID: &str = "RUST-STYLE-TYPE-001";
const MESSAGE: &str = "Do not use type aliases that only rename another type.";

enum AliasGenericParam {
	Lifetime(String),
	Type(String),
}

#[derive(Debug, Clone)]
pub(crate) struct TypeAliasRenameFix {
	pub(crate) alias: String,
	pub(crate) target: String,
	pub(crate) definition_edits: Vec<Edit>,
}

pub(crate) fn check_type_alias_renames(ctx: &FileContext, violations: &mut Vec<Violation>) {
	for type_alias in ctx.source_file.syntax().descendants().filter_map(TypeAlias::cast) {
		let Some(Type::PathType(path_type)) = type_alias.ty() else {
			continue;
		};
		let Some(aliases) = alias_generic_keys(&type_alias) else {
			continue;
		};
		let Some(rhs_path) = path_type.path() else {
			continue;
		};

		if !is_meaningless_alias(&rhs_path, &aliases) {
			continue;
		}

		let start = usize::from(path_type.syntax().text_range().start());
		let line = shared::line_from_offset(&ctx.line_starts, start);
		let fixable = type_alias_autofix_plan(ctx, &type_alias, &rhs_path, &aliases).is_some();

		shared::push_violation(violations, ctx, line, RULE_ID, MESSAGE, fixable);
	}
}

pub(crate) fn collect_type_alias_rename_fixes(ctx: &FileContext) -> Vec<TypeAliasRenameFix> {
	let mut out = Vec::new();

	for type_alias in ctx.source_file.syntax().descendants().filter_map(TypeAlias::cast) {
		let Some(Type::PathType(path_type)) = type_alias.ty() else {
			continue;
		};
		let Some(aliases) = alias_generic_keys(&type_alias) else {
			continue;
		};
		let Some(rhs_path) = path_type.path() else {
			continue;
		};
		let Some(plan) = type_alias_autofix_plan(ctx, &type_alias, &rhs_path, &aliases) else {
			continue;
		};

		out.push(plan);
	}

	out
}

pub(crate) fn build_type_alias_usage_rename_edits(
	ctx: &FileContext,
	renames: &BTreeMap<String, String>,
	skip_ranges: &[(usize, usize)],
) -> Vec<Edit> {
	if renames.is_empty() {
		return Vec::new();
	}

	let mut edits = Vec::new();

	for segment in ctx.source_file.syntax().descendants().filter_map(PathSegment::cast) {
		let Some(name_ref) = segment.name_ref() else {
			continue;
		};
		let Some(replacement) = renames.get(name_ref.text().as_str()) else {
			continue;
		};
		let range = name_ref.syntax().text_range();
		let start = usize::from(range.start());
		let end = usize::from(range.end());

		if skip_ranges.iter().any(|(skip_start, skip_end)| start < *skip_end && end > *skip_start) {
			continue;
		}

		edits.push(Edit { start, end, replacement: replacement.clone(), rule: RULE_ID });
	}

	edits
}

fn is_meaningless_alias(path: &Path, aliases: &[AliasGenericParam]) -> bool {
	let mut segments = Vec::<PathSegment>::new();

	if !collect_simple_path_segments(path, &mut segments) {
		return false;
	}
	if segments.is_empty() {
		return false;
	}

	for segment in segments.iter().take(segments.len() - 1) {
		if segment.generic_arg_list().is_some() {
			return false;
		}
	}

	let Some(last_segment) = segments.last() else {
		return false;
	};
	let Some(last_generic_args) = last_segment.generic_arg_list() else {
		return aliases.is_empty();
	};
	let rhs_args = last_generic_args.generic_args().collect::<Vec<GenericArg>>();

	if rhs_args.len() != aliases.len() {
		return false;
	}

	for (rhs_arg, alias) in rhs_args.iter().zip(aliases) {
		if !generic_arg_matches_param(rhs_arg, alias) {
			return false;
		}
	}

	true
}

fn type_alias_autofix_plan(
	ctx: &FileContext,
	type_alias: &TypeAlias,
	rhs_path: &Path,
	aliases: &[AliasGenericParam],
) -> Option<TypeAliasRenameFix> {
	if !is_meaningless_alias(rhs_path, aliases) {
		return None;
	}

	// Only automatically rewrite public aliases, since replacing the name affects callers.
	type_alias.visibility()?;

	let alias_name = type_alias.name()?.text().to_string();
	let mut rhs_segments = Vec::<PathSegment>::new();

	if !collect_simple_path_segments(rhs_path, &mut rhs_segments) || rhs_segments.is_empty() {
		return None;
	}

	let target_segment = rhs_segments.last()?;
	let target_name = target_segment.name_ref()?.text().to_string();
	let alias_start = usize::from(type_alias.syntax().text_range().start());
	let alias_end = usize::from(type_alias.syntax().text_range().end());
	let mut definition_edits = Vec::new();

	if rhs_segments.len() >= 2 {
		let rhs_text = rhs_path.syntax().text().to_string();

		definition_edits.push(Edit {
			start: alias_start,
			end: alias_end,
			replacement: format!("pub use {rhs_text};"),
			rule: RULE_ID,
		});
	} else {
		let (use_start, use_end, use_path, use_is_pub) =
			find_simple_sibling_use_importing_ident(ctx, type_alias, target_name.as_str())?;

		if use_is_pub {
			// The target is already exported; remove the alias and rewrite callers.
			definition_edits.push(Edit {
				start: alias_start,
				end: alias_end,
				replacement: String::new(),
				rule: RULE_ID,
			});
		} else {
			definition_edits.push(Edit {
				start: alias_start,
				end: alias_end,
				replacement: format!("pub use {use_path};"),
				rule: RULE_ID,
			});
			definition_edits.push(Edit {
				start: use_start,
				end: use_end,
				replacement: String::new(),
				rule: RULE_ID,
			});
		}
	}

	Some(TypeAliasRenameFix { alias: alias_name, target: target_name, definition_edits })
}

fn simple_use_path_text(text: &str) -> Option<String> {
	let text = text.trim();
	let start = text.find("use")?;
	let after = text.get(start + 3..)?;
	let bytes = after.as_bytes();
	let mut idx = 0_usize;

	while idx < bytes.len() && bytes[idx].is_ascii_whitespace() {
		idx += 1;
	}

	let tail = after.get(idx..)?;
	let semi = tail.find(';')?;
	let use_path = tail[..semi].trim();

	if use_path.is_empty()
		|| use_path.contains('{')
		|| use_path.contains('}')
		|| use_path.contains('*')
		|| use_path.contains(" as ")
	{
		return None;
	}

	Some(use_path.to_string())
}

fn find_simple_sibling_use_importing_ident(
	ctx: &FileContext,
	type_alias: &TypeAlias,
	ident: &str,
) -> Option<(usize, usize, String, bool)> {
	let parent = type_alias.syntax().parent()?;

	for use_item in ctx.source_file.syntax().descendants().filter_map(Use::cast) {
		if use_item.syntax().parent() != Some(parent.clone()) {
			continue;
		}

		let path_text = simple_use_path_text(&use_item.syntax().text().to_string())?;
		let last = path_text.rsplit("::").next().unwrap_or(path_text.as_str()).trim();

		if last != ident {
			continue;
		}

		let start = usize::from(use_item.syntax().text_range().start());
		let end = usize::from(use_item.syntax().text_range().end());
		let is_pub = use_item.visibility().is_some();

		return Some((start, end, path_text, is_pub));
	}

	None
}

fn generic_arg_matches_param(arg: &GenericArg, alias: &AliasGenericParam) -> bool {
	match (arg, alias) {
		(ast::GenericArg::LifetimeArg(lifetime_arg), AliasGenericParam::Lifetime(expected)) => {
			let Some(lifetime) = lifetime_arg.lifetime() else {
				return false;
			};
			let Some(token) = lifetime.lifetime_ident_token() else {
				return false;
			};

			token.text() == expected.as_str()
		},
		(ast::GenericArg::TypeArg(type_arg), AliasGenericParam::Type(expected)) => {
			let Some(type_arg_type) = type_arg.ty() else {
				return false;
			};
			let Type::PathType(path_type) = type_arg_type else {
				return false;
			};
			let Some(path) = path_type.path() else {
				return false;
			};
			let mut segments = Vec::<PathSegment>::new();

			if !collect_simple_path_segments(&path, &mut segments) {
				return false;
			}
			if segments.len() != 1 {
				return false;
			}

			let Some(name_ref) = segments[0].name_ref() else {
				return false;
			};

			name_ref.text() == expected.as_str()
		},
		_ => false,
	}
}

fn alias_generic_keys(type_alias: &TypeAlias) -> Option<Vec<AliasGenericParam>> {
	let Some(generic_params) = type_alias.generic_param_list() else {
		return Some(Vec::new());
	};
	let mut out = Vec::new();

	for param in generic_params.generic_params() {
		match param {
			GenericParam::TypeParam(type_param) => {
				// A default generic parameter (for example `E = Error`) changes the alias API
				// surface, so it is not considered a pure rename.
				if type_param
					.syntax()
					.children_with_tokens()
					.any(|token| token.kind() == SyntaxKind::EQ)
				{
					return None;
				}

				let name = type_param.name()?;

				out.push(AliasGenericParam::Type(name.text().to_string()));
			},
			GenericParam::LifetimeParam(lifetime_param) => {
				let lifetime = lifetime_param.lifetime()?;
				let token = lifetime.lifetime_ident_token()?;

				out.push(AliasGenericParam::Lifetime(token.text().to_string()));
			},
			GenericParam::ConstParam(_) => return None,
		}
	}

	Some(out)
}

fn collect_simple_path_segments(path: &Path, out: &mut Vec<PathSegment>) -> bool {
	if let Some(qualifier) = path.qualifier()
		&& !collect_simple_path_segments(&qualifier, out)
	{
		return false;
	}

	let Some(segment) = path.segment() else {
		return false;
	};

	if segment.type_anchor().is_some()
		|| segment.parenthesized_arg_list().is_some()
		|| segment.ret_type().is_some()
		|| segment.return_type_syntax().is_some()
	{
		return false;
	}

	out.push(segment);

	true
}