//! emit 前置 pass：builtin 引用预扫描 + 声明预登记。
//!
//! 在生成临时寄存器前遍历 AST，把内置全局标识符预先登记到固定寄存器槽
//! （builtin_reg_map），避免与临时寄存器池冲突；同时预声明函数/var 声明，
//! 支持提升语义。

use crate::{CompileCtx, Emitter};
use oxide_parser::{Expression, Statement, VariableDeclarationKind};

impl Emitter {

    /// builtin slot allocation ahead of the temporary register pool.
    pub(crate) fn pre_register_builtin_references(&self, stmts: &[Statement], ctx: &mut CompileCtx) {
        for stmt in stmts {
            self.pre_scan_builtin_stmt(stmt, ctx);
        }
    }

    fn pre_scan_builtin_stmt(&self, stmt: &Statement, ctx: &mut CompileCtx) {
        match stmt {
            Statement::ExpressionStatement(es) => self.pre_scan_builtin_expr(&es.expression, ctx),
            Statement::VariableDeclaration(vd) => {
                for d in &vd.declarations {
                    if let Some(init) = &d.init {
                        self.pre_scan_builtin_expr(init, ctx);
                    }
                }
            }
            Statement::ReturnStatement(rs) => {
                if let Some(a) = &rs.argument {
                    self.pre_scan_builtin_expr(a, ctx);
                }
            }
            Statement::IfStatement(is) => {
                self.pre_scan_builtin_expr(&is.test, ctx);
                self.pre_scan_builtin_stmt(&is.consequent, ctx);
                if let Some(alt) = &is.alternate {
                    self.pre_scan_builtin_stmt(alt, ctx);
                }
            }
            Statement::WhileStatement(wh) => {
                self.pre_scan_builtin_expr(&wh.test, ctx);
                self.pre_scan_builtin_stmt(&wh.body, ctx);
            }
            Statement::DoWhileStatement(dw) => {
                self.pre_scan_builtin_stmt(&dw.body, ctx);
                self.pre_scan_builtin_expr(&dw.test, ctx);
            }
            Statement::ForStatement(fs) => {
                if let Some(init) = &fs.init {
                    if let Some(e) = init.as_expression() {
                        self.pre_scan_builtin_expr(e, ctx);
                    } else if let oxide_parser::ForStatementInit::VariableDeclaration(decl) = init {
                        for d in &decl.declarations {
                            if let Some(init_expr) = &d.init {
                                self.pre_scan_builtin_expr(init_expr, ctx);
                            }
                        }
                    }
                }
                if let Some(t) = &fs.test {
                    self.pre_scan_builtin_expr(t, ctx);
                }
                if let Some(u) = &fs.update {
                    self.pre_scan_builtin_expr(u, ctx);
                }
                self.pre_scan_builtin_stmt(&fs.body, ctx);
            }
            Statement::ForInStatement(fi) => {
                self.pre_scan_builtin_expr(&fi.right, ctx);
                self.pre_scan_builtin_stmt(&fi.body, ctx);
            }
            Statement::ForOfStatement(fo) => {
                self.pre_scan_builtin_expr(&fo.right, ctx);
                self.pre_scan_builtin_stmt(&fo.body, ctx);
            }
            Statement::SwitchStatement(sw) => {
                self.pre_scan_builtin_expr(&sw.discriminant, ctx);
                for case in &sw.cases {
                    if let Some(test) = &case.test {
                        self.pre_scan_builtin_expr(test, ctx);
                    }
                    for s in &case.consequent {
                        self.pre_scan_builtin_stmt(s, ctx);
                    }
                }
            }
            Statement::ThrowStatement(ts) => {
                self.pre_scan_builtin_expr(&ts.argument, ctx);
            }
            Statement::TryStatement(ts) => {
                for s in &ts.block.body {
                    self.pre_scan_builtin_stmt(s, ctx);
                }
                if let Some(handler) = &ts.handler {
                    for s in &handler.body.body {
                        self.pre_scan_builtin_stmt(s, ctx);
                    }
                }
                if let Some(finalizer) = &ts.finalizer {
                    for s in &finalizer.body {
                        self.pre_scan_builtin_stmt(s, ctx);
                    }
                }
            }
            Statement::BlockStatement(bs) => {
                for s in &bs.body {
                    self.pre_scan_builtin_stmt(s, ctx);
                }
            }
            Statement::LabeledStatement(ls) => self.pre_scan_builtin_stmt(&ls.body, ctx),
            Statement::ClassDeclaration(cd) => {
                if let Some(super_class) = &cd.super_class {
                    self.pre_scan_builtin_expr(super_class, ctx);
                }
            }
            Statement::FunctionDeclaration(_) | Statement::BreakStatement(_) | Statement::ContinueStatement(_) => {}
            _ => {}
        }
    }

    fn pre_scan_builtin_expr(&self, expr: &Expression, ctx: &mut CompileCtx) {
        match expr {
            Expression::Identifier(ident) => {
                if CompileCtx::is_known_builtin(ident.name.as_str()) {
                    let _ = ctx.lookup_or_builtin(ident.name.as_str());
                }
            }
            Expression::BinaryExpression(bin) => {
                self.pre_scan_builtin_expr(&bin.left, ctx);
                self.pre_scan_builtin_expr(&bin.right, ctx);
            }
            Expression::UnaryExpression(un) => {
                self.pre_scan_builtin_expr(&un.argument, ctx);
            }
            Expression::CallExpression(call) => {
                self.pre_scan_builtin_expr(&call.callee, ctx);
                for arg in &call.arguments {
                    if let Some(e) = arg.as_expression() {
                        self.pre_scan_builtin_expr(e, ctx);
                    }
                }
            }
            Expression::NewExpression(ne) => {
                self.pre_scan_builtin_expr(&ne.callee, ctx);
                for arg in &ne.arguments {
                    if let Some(e) = arg.as_expression() {
                        self.pre_scan_builtin_expr(e, ctx);
                    }
                }
            }
            Expression::LogicalExpression(log) => {
                self.pre_scan_builtin_expr(&log.left, ctx);
                self.pre_scan_builtin_expr(&log.right, ctx);
            }
            Expression::ConditionalExpression(cond) => {
                self.pre_scan_builtin_expr(&cond.test, ctx);
                self.pre_scan_builtin_expr(&cond.consequent, ctx);
                self.pre_scan_builtin_expr(&cond.alternate, ctx);
            }
            Expression::PrivateInExpression(pin) => {
                self.pre_scan_builtin_expr(&pin.right, ctx);
            }
            Expression::SequenceExpression(seq) => {
                for e in &seq.expressions {
                    self.pre_scan_builtin_expr(e, ctx);
                }
            }
            Expression::AssignmentExpression(assign) => {
                if let Some(target) = assign.left.as_simple_assignment_target() {
                    self.pre_scan_builtin_target(target, ctx);
                }
                self.pre_scan_builtin_expr(&assign.right, ctx);
            }
            Expression::UpdateExpression(update) => {
                self.pre_scan_builtin_target(&update.argument, ctx);
            }
            Expression::TemplateLiteral(tl) => {
                for e in &tl.expressions {
                    self.pre_scan_builtin_expr(e, ctx);
                }
            }
            Expression::TaggedTemplateExpression(tt) => {
                self.pre_scan_builtin_expr(&tt.tag, ctx);
                for e in &tt.quasi.expressions {
                    self.pre_scan_builtin_expr(e, ctx);
                }
            }
            Expression::ObjectExpression(obj) => {
                for prop in &obj.properties {
                    if let oxide_parser::ObjectPropertyKind::ObjectProperty(p) = prop {
                        if p.computed {
                            self.pre_scan_builtin_expr(p.key.to_expression(), ctx);
                        }
                        self.pre_scan_builtin_expr(&p.value, ctx);
                    }
                }
            }
            Expression::ArrayExpression(arr) => {
                for e in &arr.elements {
                    if let Some(e) = e.as_expression() {
                        self.pre_scan_builtin_expr(e, ctx);
                    }
                }
            }
            Expression::PrivateFieldExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
            }
            Expression::StaticMemberExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
            }
            Expression::ComputedMemberExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
                self.pre_scan_builtin_expr(&member.expression, ctx);
            }
            Expression::ChainExpression(chain) => {
                self.pre_scan_builtin_chain(&chain.expression, ctx);
            }
            Expression::ParenthesizedExpression(p) => self.pre_scan_builtin_expr(&p.expression, ctx),
            Expression::ArrowFunctionExpression(_)
            | Expression::FunctionExpression(_)
            | Expression::ClassExpression(_) => {}
            _ => {}
        }
    }

    fn pre_scan_builtin_target(&self, target: &oxide_parser::SimpleAssignmentTarget, ctx: &mut CompileCtx) {
        match target {
            oxide_parser::SimpleAssignmentTarget::StaticMemberExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
            }
            oxide_parser::SimpleAssignmentTarget::ComputedMemberExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
                self.pre_scan_builtin_expr(&member.expression, ctx);
            }
            oxide_parser::SimpleAssignmentTarget::PrivateFieldExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
            }
            _ => {}
        }
    }

    fn pre_scan_builtin_chain(&self, element: &oxide_parser::ChainElement, ctx: &mut CompileCtx) {
        match element {
            oxide_parser::ChainElement::StaticMemberExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
            }
            oxide_parser::ChainElement::ComputedMemberExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
                self.pre_scan_builtin_expr(&member.expression, ctx);
            }
            oxide_parser::ChainElement::PrivateFieldExpression(member) => {
                self.pre_scan_builtin_expr(&member.object, ctx);
            }
            oxide_parser::ChainElement::CallExpression(call) => {
                self.pre_scan_builtin_expr(&call.callee, ctx);
                for arg in &call.arguments {
                    if let Some(e) = arg.as_expression() {
                        self.pre_scan_builtin_expr(e, ctx);
                    }
                }
            }
            _ => {}
        }
    }


    pub(crate) fn predeclare_function_declarations(&self, statements: &[Statement], ctx: &mut CompileCtx) {
        for statement in statements {
            let Statement::FunctionDeclaration(function) = statement else {
                continue;
            };
            let Some(identifier) = &function.id else {
                continue;
            };
            let reg = ctx.alloc_reg();
            let _ = ctx.declare_initialized(identifier.name.as_str(), reg, VariableDeclarationKind::Var, false);
        }
    }

    /// Pre-declare all `var` bindings in this statement list so hoisted function
    /// declarations emitted earlier can resolve them. Mirrors the removed count
    /// pass behavior (see fe8bd86): top-level `var` names must be visible while
    /// compiling function bodies that close over them.
    pub(crate) fn predeclare_var_declarations(&self, statements: &[Statement], ctx: &mut CompileCtx) {
        for statement in statements {
            match statement {
                Statement::VariableDeclaration(decl) => {
                    if !matches!(decl.kind, VariableDeclarationKind::Var) {
                        continue;
                    }
                    for d in &decl.declarations {
                        if let oxide_parser::BindingPattern::BindingIdentifier(bi) = &d.id {
                            let reg = ctx.alloc_reg();
                            let _ = ctx.declare_initialized(bi.name.as_str(), reg, VariableDeclarationKind::Var, false);
                        }
                    }
                }
                Statement::BlockStatement(bs) => self.predeclare_var_declarations(&bs.body, ctx),
                Statement::IfStatement(is) => {
                    self.predeclare_var_declarations(std::slice::from_ref(&is.consequent), ctx);
                    if let Some(alt) = &is.alternate {
                        self.predeclare_var_declarations(std::slice::from_ref(alt), ctx);
                    }
                }
                Statement::WhileStatement(wh) => {
                    self.predeclare_var_declarations(std::slice::from_ref(&wh.body), ctx);
                }
                Statement::DoWhileStatement(dw) => {
                    self.predeclare_var_declarations(std::slice::from_ref(&dw.body), ctx);
                }
                Statement::ForStatement(fs) => {
                    if let Some(oxide_parser::ForStatementInit::VariableDeclaration(decl)) = &fs.init {
                        if matches!(decl.kind, VariableDeclarationKind::Var) {
                            for d in &decl.declarations {
                                if let oxide_parser::BindingPattern::BindingIdentifier(bi) = &d.id {
                                    let reg = ctx.alloc_reg();
                                    let _ =
                                        ctx.declare_initialized(bi.name.as_str(), reg, VariableDeclarationKind::Var, false);
                                }
                            }
                        }
                    }
                    self.predeclare_var_declarations(std::slice::from_ref(&fs.body), ctx);
                }
                Statement::SwitchStatement(sw) => {
                    for case in &sw.cases {
                        self.predeclare_var_declarations(&case.consequent, ctx);
                    }
                }
                Statement::TryStatement(ts) => {
                    self.predeclare_var_declarations(&ts.block.body, ctx);
                    if let Some(handler) = &ts.handler {
                        self.predeclare_var_declarations(&handler.body.body, ctx);
                    }
                    if let Some(finalizer) = &ts.finalizer {
                        self.predeclare_var_declarations(&finalizer.body, ctx);
                    }
                }
                Statement::LabeledStatement(ls) => {
                    self.predeclare_var_declarations(std::slice::from_ref(&ls.body), ctx);
                }
                _ => {}
            }
        }
    }

}