//! JoinIR routing logic for loop lowering

use crate::ast::ASTNode;
use crate::mir::builder::MirBuilder;
use crate::mir::ValueId;

impl MirBuilder {
    /// 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)
    pub(in crate::mir::builder) fn try_cf_loop_joinir(
        &mut self,
        condition: &ASTNode,
        body: &[ASTNode],
    ) -> Result<Option<ValueId>, String> {
        // Get current function name
        let func_name = self
            .current_function
            .as_ref()
            .map(|f| f.signature.name.clone())
            .unwrap_or_default();

        eprintln!("[cf_loop/joinir/router] try_cf_loop_joinir called for function: '{}'", func_name);

        // Phase 188-Impl-3: Debug logging for function name routing
        if std::env::var("NYASH_JOINIR_MAINLINE_DEBUG").is_ok() {
            eprintln!("[cf_loop/joinir/router] Current function name: '{}'", func_name);
        }

        // Phase 49-4 + Phase 80: Multi-target routing
        // - Core ON なら代表2本（print_tokens / ArrayExt.filter）は JoinIR を優先し、失敗したら LoopBuilder へフォールバック
        // - Core OFF では従来通り dev フラグで opt-in
        // Note: Arity does NOT include implicit `me` receiver
        // Phase 188: Add "main" routing for loop pattern expansion
        let core_on = crate::config::env::joinir_core_enabled();
        let is_target = match func_name.as_str() {
            "main" => true,  // Phase 188-Impl-1: Enable JoinIR for main function (Pattern 1)
            "JoinIrMin.main/0" => true,  // Phase 188-Impl-2: Enable JoinIR for JoinIrMin.main/0 (Pattern 2)
            "JsonTokenizer.print_tokens/0" => {
                if core_on {
                    true
                } else {
                    std::env::var("HAKO_JOINIR_PRINT_TOKENS_MAIN")
                        .ok()
                        .as_deref()
                        == Some("1")
                }
            }
            "ArrayExtBox.filter/2" => {
                if core_on {
                    true
                } else {
                    std::env::var("HAKO_JOINIR_ARRAY_FILTER_MAIN")
                        .ok()
                        .as_deref()
                        == Some("1")
                }
            }
            _ => false,
        };

        if !is_target {
            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();
        eprintln!("[cf_loop/joinir] DEBUG FLAG STATUS: debug={}, NYASH_LOOPFORM_DEBUG={:?}, NYASH_JOINIR_MAINLINE_DEBUG={:?}",
            debug,
            std::env::var("NYASH_LOOPFORM_DEBUG"),
            std::env::var("NYASH_JOINIR_MAINLINE_DEBUG"));
        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 → JSON v0 format (with "defs" array)
    /// 2. AstToJoinIrLowerer::lower_program_json() → JoinModule
    /// 3. convert_join_module_to_mir_with_meta() → MirModule
    /// 4. Merge MIR blocks into current_function
    ///
    /// # Phase 49-4 Note
    ///
    /// JoinIR Frontend expects a complete function definition with:
    /// - local variable initializations
    /// - loop body
    /// - return statement
    ///
    /// Since cf_loop only has access to the loop condition and body,
    /// we construct a minimal JSON v0 wrapper with function name "simple"
    /// to match the JoinIR Frontend's expected pattern.
    pub(in crate::mir::builder) fn cf_loop_joinir_impl(
        &mut self,
        condition: &ASTNode,
        body: &[ASTNode],
        func_name: &str,
        debug: bool,
    ) -> Result<Option<ValueId>, String> {
        use super::super::super::loop_frontend_binding::LoopFrontendBinding;
        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;
        use crate::mir::MirInstruction;
        use crate::r#macro::ast_json::ast_to_json;

        // Phase 194: Use table-driven router instead of if/else chain
        // This makes adding new patterns trivial - just add an entry to LOOP_PATTERNS table
        use super::patterns::{route_loop_pattern, LoopPatternContext};

        let ctx = LoopPatternContext::new(condition, body, &func_name, debug);
        if let Some(result) = route_loop_pattern(self, &ctx)? {
            if debug {
                eprintln!("[cf_loop/joinir] Pattern router succeeded for '{}'", func_name);
            }
            return Ok(Some(result));
        }

        if debug {
            eprintln!("[cf_loop/joinir] Pattern router found no match for '{}', continuing to legacy path", func_name);
        }

        // Phase 50: Create appropriate binding based on function name
        let binding = match func_name {
            "JsonTokenizer.print_tokens/0" => LoopFrontendBinding::for_print_tokens(),
            "ArrayExtBox.filter/2" => LoopFrontendBinding::for_array_filter(),
            _ => {
                if debug {
                    eprintln!(
                        "[cf_loop/joinir] No binding defined for {}, falling back",
                        func_name
                    );
                }
                return Ok(None);
            }
        };

        if debug {
            eprintln!(
                "[cf_loop/joinir] Using binding: counter={}, acc={:?}, pattern={:?}",
                binding.counter_var, binding.accumulator_var, binding.pattern
            );
        }

        // Step 1: Convert condition and body to JSON
        let condition_json = ast_to_json(condition);
        let mut body_json: Vec<serde_json::Value> = body.iter().map(|s| ast_to_json(s)).collect();

        // Phase 50: Rename variables in body (e.g., "out" → "acc" for filter)
        binding.rename_body_variables(&mut body_json);

        // Phase 50: Generate Local declarations from binding
        let (i_local, acc_local, n_local) = binding.generate_local_declarations();

        // Phase 52/56: Build params from external_refs
        // Instance methods need `me`, static methods need their parameters (arr, pred, etc.)
        let mut params: Vec<serde_json::Value> = Vec::new();

        // Phase 52: Add 'me' for instance methods
        if binding.needs_me_receiver() {
            if debug {
                eprintln!("[cf_loop/joinir] Adding 'me' to params (instance method)");
            }
            params.push(serde_json::json!("me"));
        }

        // Phase 56: Add external_refs as parameters (arr, pred for filter)
        for ext_ref in &binding.external_refs {
            // Skip "me" and "me.*" as they're handled above
            if ext_ref == "me" || ext_ref.starts_with("me.") {
                continue;
            }
            if debug {
                eprintln!(
                    "[cf_loop/joinir] Adding '{}' to params (external_ref)",
                    ext_ref
                );
            }
            params.push(serde_json::json!(ext_ref));
        }

        // Step 2: Construct JSON v0 format with "defs" array
        // The function is named "simple" to match JoinIR Frontend's pattern matching
        // Phase 50: Include i/acc/n Local declarations to satisfy JoinIR Frontend expectations
        let program_json = serde_json::json!({
            "defs": [
                {
                    "name": "simple",
                    "params": params,
                    "body": {
                        "type": "Block",
                        "body": [
                            // Phase 50: Inject i/acc/n Local declarations
                            i_local,
                            acc_local,
                            n_local,
                            {
                                "type": "Loop",
                                "cond": condition_json,  // JoinIR Frontend expects "cond" not "condition"
                                "body": body_json
                            },
                            // Return the accumulator (or null for side-effect loops)
                            {
                                "type": "Return",
                                "value": { "kind": "Variable", "name": "acc" }
                            }
                        ]
                    }
                }
            ]
        });

        if debug {
            eprintln!(
                "[cf_loop/joinir] Generated JSON v0 for {}: {}",
                func_name,
                serde_json::to_string_pretty(&program_json).unwrap_or_default()
            );
        }

        // Step 3: Lower to JoinIR
        // Phase 49-4: Use catch_unwind for graceful fallback on unsupported patterns
        // The JoinIR Frontend may panic if the loop doesn't match expected patterns
        // (e.g., missing variable initializations like "i must be initialized")
        let join_module = {
            let json_clone = program_json.clone();
            let result = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
                let mut lowerer = AstToJoinIrLowerer::new();
                lowerer.lower_program_json(&json_clone)
            }));

            match result {
                Ok(module) => module,
                Err(e) => {
                    // Extract panic message for debugging
                    let panic_msg = if let Some(s) = e.downcast_ref::<&str>() {
                        s.to_string()
                    } else if let Some(s) = e.downcast_ref::<String>() {
                        s.clone()
                    } else {
                        "unknown panic".to_string()
                    };

                    if debug {
                        eprintln!(
                            "[cf_loop/joinir] JoinIR lowering failed for {}: {}, falling back to legacy",
                            func_name, panic_msg
                        );
                    }
                    // Return None to fall back to legacy LoopBuilder
                    return Ok(None);
                }
            }
        };
        // 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()
            );
            for (name, func) in &mir_module.functions {
                eprintln!(
                    "[cf_loop/joinir]   - {}: {} blocks, entry={:?}",
                    name,
                    func.blocks.len(),
                    func.entry_block
                );
                // Phase 189: Debug - show block contents
                for (block_id, block) in &func.blocks {
                    eprintln!("[cf_loop/joinir]     Block {:?}: {} instructions", block_id, block.instructions.len());
                    for (i, inst) in block.instructions.iter().enumerate() {
                        eprintln!("[cf_loop/joinir]       [{}] {:?}", i, inst);
                    }
                    if let Some(ref term) = block.terminator {
                        eprintln!("[cf_loop/joinir]       terminator: {:?}", term);
                    }
                }
            }
        }

        // 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
        // Phase 188-Impl-3: Pass None for boundary (legacy path without boundary)
        // Phase 189: Discard exit PHI result (legacy path doesn't need it)
        let _ = self.merge_joinir_mir_blocks(&mir_module, None, 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))
    }
}