//! Control-flow entrypoints (if/loop/try/throw) centralized here.
//!
//! This module is being modularized in phases:
//! - Phase 1: Debug utilities (debug.rs) ✅
//! - Phase 2: Pattern lowerers (joinir/patterns/) ✅
//! - Phase 3: JoinIR routing (joinir/routing.rs) ✅
//! - Phase 4-19: Additional modularization (future)

use super::{Effect, EffectMask, MirInstruction, ValueId};
use crate::ast::ASTNode;

// Phase 1: Debug utilities
pub(in crate::mir::builder) mod debug;

// Phase 2: JoinIR integration (patterns)
pub(in crate::mir::builder) mod joinir;

impl super::MirBuilder {
    /// Control-flow: block
    pub(super) fn cf_block(&mut self, statements: Vec<ASTNode>) -> Result<ValueId, String> {
        // identical to build_block; kept here for future policy hooks
        self.build_block(statements)
    }

    /// Control-flow: if
    ///
    /// # Phase 124: JoinIR-Only (hako_check専用化完了)
    ///
    /// If statements are now always routed through the canonical lowering path
    /// (lower_if_form), which internally uses JoinIR-based PHI generation.
    ///
    /// Phase 123 の環境変数による分岐は削除済み。
    pub(super) fn cf_if(
        &mut self,
        condition: ASTNode,
        then_branch: ASTNode,
        else_branch: Option<ASTNode>,
    ) -> Result<ValueId, String> {
        // Phase 124: JoinIR-only path (環境変数分岐削除)
        // lower_if_form は JoinIR ベースの PHI 生成を使用
        self.lower_if_form(condition, then_branch, else_branch)
    }

    /// Control-flow: loop
    ///
    /// # Phase 49: JoinIR Frontend Mainline Integration
    ///
    /// This is the unified entry point for all loop lowering. Specific functions
    /// are routed through JoinIR Frontend instead of the traditional LoopBuilder path
    /// when enabled via dev flags (Phase 49) or Core policy (Phase 80):
    ///
    /// - Core ON (`joinir_core_enabled()`): print_tokens / ArrayExt.filter はまず JoinIR Frontend を試す
    /// - Dev フラグ（既存）:
    ///   - `HAKO_JOINIR_PRINT_TOKENS_MAIN=1`: JsonTokenizer.print_tokens/0
    ///   - `HAKO_JOINIR_ARRAY_FILTER_MAIN=1`: ArrayExtBox.filter/2
    ///
    /// Note: Arity does NOT include implicit `me` receiver.
    pub(super) fn cf_loop(
        &mut self,
        condition: ASTNode,
        body: Vec<ASTNode>,
    ) -> Result<ValueId, String> {
        // Phase 49/80: Try JoinIR Frontend route for mainline targets
        if let Some(result) = self.try_cf_loop_joinir(&condition, &body)? {
            return Ok(result);
        }

        if std::env::var("NYASH_LOOPFORM_DEBUG").is_ok() {
            eprintln!("[cf_loop] CALLED from somewhere");
            eprintln!("[cf_loop] Current stack (simulated): check build_statement vs build_expression_impl");
        }

        // Phase 186: LoopBuilder Hard Freeze - Legacy path disabled
        // Phase 187-2: LoopBuilder module removed - all loops must use JoinIR
        return Err(format!(
            "[joinir/freeze] Loop lowering failed: JoinIR does not support this pattern, and LoopBuilder has been removed.\n\
             Function: {}\n\
             Hint: This loop pattern is not supported. All loops must use JoinIR lowering.",
            self.current_function.as_ref().map(|f| f.signature.name.as_str()).unwrap_or("<unknown>")
        ));
    }

    /// Phase 49: Try JoinIR Frontend for mainline integration
    ///
    /// Returns `Ok(Some(value))` if the current function should use JoinIR Frontend,
    /// `Ok(None)` to fall through to the legacy LoopBuilder path.
    ///
    /// # Phase 49-4: Multi-target support
    ///
    /// Targets are enabled via separate dev flags:
    /// - `HAKO_JOINIR_PRINT_TOKENS_MAIN=1`: JsonTokenizer.print_tokens/0
    /// - `HAKO_JOINIR_ARRAY_FILTER_MAIN=1`: ArrayExtBox.filter/2
    ///
    /// Note: Arity in function names does NOT include implicit `me` receiver.
    /// - Instance method `print_tokens()` → `/0` (no explicit params)
    /// - Static method `filter(arr, pred)` → `/2` (two params)

    /// Phase 49-3.2: Merge JoinIR-generated MIR blocks into current_function
    ///
    /// **Phase 4 Refactoring Complete**: This function now delegates to the modular
    /// merge implementation in `joinir::merge::merge_joinir_mir_blocks()`.
    ///
    /// The original 714-line implementation has been broken down into 6 focused modules:
    /// 1. block_allocator.rs - Block ID allocation
    /// 2. value_collector.rs - Value collection
    /// 3. ID remapping (using JoinIrIdRemapper)
    /// 4. instruction_rewriter.rs - Instruction rewriting
    /// 5. exit_phi_builder.rs - Exit PHI construction
    /// 6. Boundary reconnection (in merge/mod.rs)
    fn merge_joinir_mir_blocks(
        &mut self,
        mir_module: &crate::mir::MirModule,
        boundary: Option<&crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary>,
        debug: bool,
    ) -> Result<Option<ValueId>, String> {
        // Phase 4: Delegate to modular implementation
        joinir::merge::merge_joinir_mir_blocks(self, mir_module, boundary, debug)
    }

    /// Control-flow: try/catch/finally
    pub(super) fn cf_try_catch(
        &mut self,
        try_body: Vec<ASTNode>,
        catch_clauses: Vec<crate::ast::CatchClause>,
        finally_body: Option<Vec<ASTNode>>,
    ) -> Result<ValueId, String> {
        if std::env::var("NYASH_BUILDER_DISABLE_TRYCATCH")
            .ok()
            .as_deref()
            == Some("1")
        {
            let try_ast = ASTNode::Program {
                statements: try_body,
                span: crate::ast::Span::unknown(),
            };
            let result = self.build_expression(try_ast)?;
            return Ok(result);
        }

        let try_block = self.block_gen.next();
        let catch_block = self.block_gen.next();
        let finally_block = if finally_body.is_some() {
            Some(self.block_gen.next())
        } else {
            None
        };
        let exit_block = self.block_gen.next();

        // Snapshot deferred-return state
        let saved_defer_active = self.return_defer_active;
        let saved_defer_slot = self.return_defer_slot;
        let saved_defer_target = self.return_defer_target;
        let saved_deferred_flag = self.return_deferred_emitted;
        let saved_in_cleanup = self.in_cleanup_block;
        let saved_allow_ret = self.cleanup_allow_return;
        let saved_allow_throw = self.cleanup_allow_throw;

        let ret_slot = self.next_value_id();
        self.return_defer_active = true;
        self.return_defer_slot = Some(ret_slot);
        self.return_deferred_emitted = false;
        self.return_defer_target = Some(finally_block.unwrap_or(exit_block));

        if let Some(catch_clause) = catch_clauses.first() {
            if std::env::var("NYASH_DEBUG_TRYCATCH").ok().as_deref() == Some("1") {
                eprintln!(
                    "[BUILDER] Emitting catch handler for {:?}",
                    catch_clause.exception_type
                );
            }
            let exception_value = self.next_value_id();
            self.emit_instruction(MirInstruction::Catch {
                exception_type: catch_clause.exception_type.clone(),
                exception_value,
                handler_bb: catch_block,
            })?;
        }

        // Enter try block
        crate::mir::builder::emission::branch::emit_jump(self, try_block)?;
        self.start_new_block(try_block)?;
        let try_ast = ASTNode::Program {
            statements: try_body,
            span: crate::ast::Span::unknown(),
        };
        let _try_result = self.build_expression(try_ast)?;
        if !self.is_current_block_terminated() {
            let next_target = finally_block.unwrap_or(exit_block);
            crate::mir::builder::emission::branch::emit_jump(self, next_target)?;
        }

        // Catch block
        self.start_new_block(catch_block)?;
        if std::env::var("NYASH_DEBUG_TRYCATCH").ok().as_deref() == Some("1") {
            eprintln!("[BUILDER] Enter catch block {:?}", catch_block);
        }
        if let Some(catch_clause) = catch_clauses.first() {
            let catch_ast = ASTNode::Program {
                statements: catch_clause.body.clone(),
                span: crate::ast::Span::unknown(),
            };
            self.build_expression(catch_ast)?;
        }
        if !self.is_current_block_terminated() {
            let next_target = finally_block.unwrap_or(exit_block);
            crate::mir::builder::emission::branch::emit_jump(self, next_target)?;
        }

        // Finally
        let mut cleanup_terminated = false;
        if let (Some(finally_block_id), Some(finally_statements)) = (finally_block, finally_body) {
            self.start_new_block(finally_block_id)?;
            self.in_cleanup_block = true;
            self.cleanup_allow_return = crate::config::env::cleanup_allow_return();
            self.cleanup_allow_throw = crate::config::env::cleanup_allow_throw();
            self.return_defer_active = false; // do not defer inside cleanup

            let finally_ast = ASTNode::Program {
                statements: finally_statements,
                span: crate::ast::Span::unknown(),
            };
            self.build_expression(finally_ast)?;
            cleanup_terminated = self.is_current_block_terminated();
            if !cleanup_terminated {
                crate::mir::builder::emission::branch::emit_jump(self, exit_block)?;
            }
            self.in_cleanup_block = false;
        }

        // Exit block
        self.start_new_block(exit_block)?;
        let result = if self.return_deferred_emitted && !cleanup_terminated {
            self.emit_instruction(MirInstruction::Return {
                value: Some(ret_slot),
            })?;
            crate::mir::builder::emission::constant::emit_void(self)
        } else {
            crate::mir::builder::emission::constant::emit_void(self)
        };

        // Restore context
        self.return_defer_active = saved_defer_active;
        self.return_defer_slot = saved_defer_slot;
        self.return_defer_target = saved_defer_target;
        self.return_deferred_emitted = saved_deferred_flag;
        self.in_cleanup_block = saved_in_cleanup;
        self.cleanup_allow_return = saved_allow_ret;
        self.cleanup_allow_throw = saved_allow_throw;

        Ok(result)
    }

    /// Phase 188-Impl-2: Extract loop variable name from condition
    ///
    /// For `i < 3`, extracts `i`.
    /// For `arr.length() > 0`, extracts `arr`.
    ///
    /// This is a minimal implementation that handles simple comparison patterns.
    fn extract_loop_variable_from_condition(&self, condition: &ASTNode) -> Result<String, String> {
        use crate::ast::BinaryOperator;

        match condition {
            ASTNode::BinaryOp {
                operator, left, ..
            } if matches!(
                operator,
                BinaryOperator::Less
                    | BinaryOperator::Greater
                    | BinaryOperator::LessEqual
                    | BinaryOperator::GreaterEqual
            ) =>
            {
                // Binary comparison: extract variable from left side
                match &**left {
                    ASTNode::Variable { name, .. } => Ok(name.clone()),
                    _ => Err(format!(
                        "[cf_loop/pattern1] Cannot extract loop variable from condition: {:?}",
                        condition
                    )),
                }
            }
            _ => Err(format!(
                "[cf_loop/pattern1] Unsupported loop condition pattern: {:?}",
                condition
            )),
        }
    }

    /// Control-flow: throw
    pub(super) fn cf_throw(&mut self, expression: ASTNode) -> Result<ValueId, String> {
        if self.in_cleanup_block && !self.cleanup_allow_throw {
            return Err("throw is not allowed inside cleanup block (enable NYASH_CLEANUP_ALLOW_THROW=1 to permit)".to_string());
        }
        if std::env::var("NYASH_BUILDER_DISABLE_THROW").ok().as_deref() == Some("1") {
            let v = self.build_expression(expression)?;
            self.emit_instruction(MirInstruction::ExternCall {
                dst: None,
                iface_name: "env.debug".to_string(),
                method_name: "trace".to_string(),
                args: vec![v],
                effects: EffectMask::PURE.add(Effect::Debug),
            })?;
            return Ok(v);
        }
        let exception_value = self.build_expression(expression)?;
        self.emit_instruction(MirInstruction::Throw {
            exception: exception_value,
            effects: EffectMask::PANIC,
        })?;
        Ok(exception_value)
    }
}