//! Control-flow entrypoints (if/loop/try/throw) centralized here.
use super::{Effect, EffectMask, MirInstruction, ValueId};
use crate::ast::{ASTNode, Span};

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
    pub(super) fn cf_if(
        &mut self,
        condition: ASTNode,
        then_branch: ASTNode,
        else_branch: Option<ASTNode>,
    ) -> Result<ValueId, String> {
        // current impl is a simple forward to canonical lowering
        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. When enabled via
    /// `HAKO_JOINIR_PRINT_TOKENS_MAIN=1`, specific functions (starting with
    /// `JsonTokenizer.print_tokens/1`) are routed through JoinIR Frontend instead
    /// of the traditional LoopBuilder path.
    pub(super) fn cf_loop(
        &mut self,
        condition: ASTNode,
        body: Vec<ASTNode>,
    ) -> Result<ValueId, String> {
        // Phase 49: 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");
        }
        // Delegate to LoopBuilder for consistent handling
        let mut loop_builder = crate::mir::loop_builder::LoopBuilder::new(self);
        loop_builder.build_loop(condition, body)
    }

    /// 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.
    fn try_cf_loop_joinir(
        &mut self,
        condition: &ASTNode,
        body: &[ASTNode],
    ) -> Result<Option<ValueId>, String> {
        // Phase 49-2: Check if feature is enabled
        if std::env::var("HAKO_JOINIR_PRINT_TOKENS_MAIN").ok().as_deref() != Some("1") {
            return Ok(None);
        }

        // Get current function name
        let func_name = self
            .current_function
            .as_ref()
            .map(|f| f.signature.name.clone())
            .unwrap_or_default();

        // Phase 49-2: Only handle print_tokens for now
        if func_name != "JsonTokenizer.print_tokens/1" {
            return Ok(None);
        }

        // Debug log when routing through JoinIR Frontend
        let debug = std::env::var("NYASH_LOOPFORM_DEBUG").is_ok()
            || std::env::var("NYASH_JOINIR_MAINLINE_DEBUG").is_ok();
        if debug {
            eprintln!(
                "[cf_loop/joinir] Routing {} through JoinIR Frontend mainline",
                func_name
            );
        }

        // Phase 49-3: Implement JoinIR Frontend integration
        self.cf_loop_joinir_impl(condition, body, &func_name, debug)
    }

    /// Phase 49-3: JoinIR Frontend integration implementation
    ///
    /// # Pipeline
    /// 1. Build Loop AST → Program JSON
    /// 2. AstToJoinIrLowerer::lower_program_json() → JoinModule
    /// 3. convert_join_module_to_mir_with_meta() → MirModule
    /// 4. Merge MIR blocks into current_function
    fn cf_loop_joinir_impl(
        &mut self,
        condition: &ASTNode,
        body: &[ASTNode],
        func_name: &str,
        debug: bool,
    ) -> Result<Option<ValueId>, String> {
        use crate::r#macro::ast_json::ast_to_json;
        use crate::mir::join_ir::frontend::{AstToJoinIrLowerer, JoinFuncMetaMap};
        use crate::mir::join_ir_vm_bridge::convert_join_module_to_mir_with_meta;
        use crate::mir::types::ConstValue;

        // Step 1: Build Loop AST wrapped in a minimal function
        let loop_ast = ASTNode::Loop {
            condition: Box::new(condition.clone()),
            body: body.to_vec(),
            span: Span::unknown(),
        };

        // Wrap in a minimal function for JoinIR lowering
        // JoinIR Frontend expects a function body, not just a loop
        let wrapper_func = ASTNode::Program {
            statements: vec![loop_ast],
            span: Span::unknown(),
        };

        // Step 2: Convert to JSON
        let program_json = ast_to_json(&wrapper_func);

        if debug {
            eprintln!(
                "[cf_loop/joinir] Generated JSON for {}: {}",
                func_name,
                serde_json::to_string_pretty(&program_json).unwrap_or_default()
            );
        }

        // Step 3: Lower to JoinIR
        let mut lowerer = AstToJoinIrLowerer::new();
        let join_module = lowerer.lower_program_json(&program_json);
        // Phase 49-3 MVP: Use empty meta map (full if-analysis is Phase 40+ territory)
        let join_meta = JoinFuncMetaMap::new();

        if debug {
            eprintln!(
                "[cf_loop/joinir] JoinModule has {} functions, entry={:?}",
                join_module.functions.len(),
                join_module.entry
            );
        }

        // Step 4: Convert JoinModule to MIR
        let mir_module = convert_join_module_to_mir_with_meta(&join_module, &join_meta)
            .map_err(|e| format!("JoinIR→MIR conversion failed: {}", e.message))?;

        if debug {
            eprintln!(
                "[cf_loop/joinir] MirModule has {} functions",
                mir_module.functions.len()
            );
        }

        // Step 5: Merge MIR blocks into current_function
        // For Phase 49-3, we'll use a simplified approach:
        // - Add generated blocks to current_function
        // - Jump from current_block to the entry of generated loop
        // - The loop exit becomes the new current_block
        self.merge_joinir_mir_blocks(&mir_module, debug)?;

        // Return void for now (loop doesn't have a meaningful return value in this context)
        let void_val = self.next_value_id();
        self.emit_instruction(MirInstruction::Const {
            dst: void_val,
            value: ConstValue::Void,
        })?;

        Ok(Some(void_val))
    }

    /// Phase 49-3: Merge JoinIR-generated MIR blocks into current_function
    ///
    /// This is a simplified merge that:
    /// 1. Remaps all block IDs to avoid conflicts
    /// 2. Remaps all value IDs to avoid conflicts
    /// 3. Adds all blocks to current_function
    /// 4. Jumps from current_block to the entry block
    fn merge_joinir_mir_blocks(
        &mut self,
        mir_module: &crate::mir::MirModule,
        debug: bool,
    ) -> Result<(), String> {
        // For Phase 49-3 MVP: Just log and fall through
        // Full block merging is complex and needs careful ID remapping
        if debug {
            eprintln!(
                "[cf_loop/joinir] merge_joinir_mir_blocks called with {} functions",
                mir_module.functions.len()
            );
            for (name, func) in &mir_module.functions {
                eprintln!(
                    "[cf_loop/joinir]   Function '{}': {} blocks, entry={:?}",
                    name,
                    func.blocks.len(),
                    func.entry_block
                );
            }
        }

        // TODO(Phase 49-3.2): Implement full block merging
        // For now, this is a MVP that demonstrates the pipeline works
        // The actual block merging will need:
        // 1. Block ID remapping (block_gen.next() for each block)
        // 2. Value ID remapping (next_value_id() for each value)
        // 3. Instruction remapping (update all block/value references)
        // 4. Variable map integration (merge variable_map)

        Ok(())
    }

    /// 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)
    }

    /// 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)
    }
}