//! Pattern Router - Table-driven dispatch for loop patterns
//!
//! Phase 194: Replace if/else chain with table-driven routing
//! Phase 193: Modularized feature extraction using ast_feature_extractor module
//!
//! # Architecture
//!
//! - Each pattern registers a detect function and a lower function
//! - Patterns are tried in priority order (lower = tried first)
//! - First matching pattern wins
//! - Feature extraction delegated to ast_feature_extractor module
//!
//! # Adding New Patterns
//!
//! 1. Create a new module in `patterns/` (e.g., `pattern4_your_name.rs`)
//! 2. Implement `pub fn can_lower(ctx: &LoopPatternContext) -> bool`
//! 3. Implement `pub fn lower(builder: &mut MirBuilder, ctx: &LoopPatternContext) -> Result<Option<ValueId>, String>`
//! 4. Add entry to `LOOP_PATTERNS` table below
//!
//! That's it! No need to modify routing logic.

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

use crate::mir::loop_pattern_detection::{LoopFeatures, LoopPatternKind};

/// Phase 193: Import AST Feature Extractor Box
/// (declared in mod.rs as pub module, import from parent)
use super::ast_feature_extractor as ast_features;

/// Phase 92 P0-2: Import LoopSkeleton for Option A
use crate::mir::loop_canonicalizer::LoopSkeleton;

/// Context passed to pattern detect/lower functions
pub(crate) struct LoopPatternContext<'a> {
    /// Loop condition AST node
    pub condition: &'a ASTNode,

    /// Loop body statements
    pub body: &'a [ASTNode],

    /// Current function name (for routing)
    pub func_name: &'a str,

    /// Debug logging enabled
    pub debug: bool,

    /// Has continue statement(s) in body? (Phase 194+)
    #[allow(dead_code)]
    pub has_continue: bool,

    /// Has break statement(s) in body? (Phase 194+)
    #[allow(dead_code)]
    pub has_break: bool,

    /// Phase 192: Loop features extracted from AST
    #[allow(dead_code)]
    pub features: LoopFeatures,

    /// Phase 192: Pattern classification based on features
    pub pattern_kind: LoopPatternKind,

    /// Phase 200-C: Optional function body AST for capture analysis
    /// None if not available, Some(&[ASTNode]) if function body is accessible
    pub fn_body: Option<&'a [ASTNode]>,

    /// Phase 92 P0-2: Optional LoopSkeleton from canonicalizer
    /// This provides ConditionalStep information for Pattern2 lowering.
    /// None if canonicalizer hasn't run yet (backward compatibility).
    /// SSOT Principle: Avoid re-detecting ConditionalStep in lowering phase.
    #[allow(dead_code)]
    pub skeleton: Option<&'a LoopSkeleton>,
}

impl<'a> LoopPatternContext<'a> {
    /// Create new context from routing parameters
    ///
    /// Phase 194+: Automatically detects continue/break statements in body
    /// Phase 192: Extract features and classify pattern from AST
    /// Phase 193: Feature extraction delegated to ast_feature_extractor module
    /// Phase 131-11: Detects infinite loop condition
    /// Phase 137-6-S1: Use choose_pattern_kind() SSOT entry point
    /// Phase 92 P0-2: Added skeleton parameter (None for backward compatibility)
    pub(crate) fn new(
        condition: &'a ASTNode,
        body: &'a [ASTNode],
        func_name: &'a str,
        debug: bool,
    ) -> Self {
        // Phase 193: Use AST Feature Extractor Box for break/continue detection
        let has_continue = ast_features::detect_continue_in_body(body);
        let has_break = ast_features::detect_break_in_body(body);

        // Phase 193: Extract features using modularized extractor
        // Phase 131-11: Pass condition for infinite loop detection
        let features = ast_features::extract_features(condition, body, has_continue, has_break);

        // Phase 137-6-S1: Use SSOT pattern selection entry point
        use crate::mir::builder::control_flow::joinir::routing::choose_pattern_kind;
        let pattern_kind = choose_pattern_kind(condition, body);

        Self {
            condition,
            body,
            func_name,
            debug,
            has_continue,
            has_break,
            features,
            pattern_kind,
            fn_body: None, // Phase 200-C: Default to None
            skeleton: None, // Phase 92 P0-2: Default to None
        }
    }

    /// Phase 200-C: Create context with fn_body for capture analysis
    pub(crate) fn with_fn_body(
        condition: &'a ASTNode,
        body: &'a [ASTNode],
        func_name: &'a str,
        debug: bool,
        fn_body: &'a [ASTNode],
    ) -> Self {
        let mut ctx = Self::new(condition, body, func_name, debug);
        ctx.fn_body = Some(fn_body);
        ctx
    }

    /// Phase 92 P0-2: Set skeleton (for canonicalizer integration)
    #[allow(dead_code)]
    pub(crate) fn with_skeleton(mut self, skeleton: &'a LoopSkeleton) -> Self {
        self.skeleton = Some(skeleton);
        self
    }
}

/// Phase 193: Feature extraction moved to ast_feature_extractor module
/// See: src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs

/// Entry in the loop pattern router table.
/// Each pattern registers a detect function and a lower function.
pub(crate) struct LoopPatternEntry {
    /// Human-readable pattern name for debugging
    pub(crate) name: &'static str,

    /// Detection function: returns true if this pattern matches
    pub(crate) detect: fn(&MirBuilder, &LoopPatternContext) -> bool,

    /// Lowering function: performs the actual JoinIR generation
    pub(crate) lower: fn(&mut MirBuilder, &LoopPatternContext) -> Result<Option<ValueId>, String>,
}

/// Static table of all registered loop patterns.
///
/// **IMPORTANT**: Patterns are tried in array order (SSOT).
/// Array order defines priority - earlier entries are tried first.
/// Pattern5 (most specific) → Pattern4 → Pattern3 → Pattern1 → Pattern2
///
/// # Current Patterns (Phase 131-11: Pattern 5 added)
///
/// All patterns now use structure-based detection via LoopFeatures and classify():
///
/// - Pattern 5: Infinite Loop with Early Exit (llvm_stage3_loop_only.hako) [Phase 131-11]
///   - Detection: pattern_kind == InfiniteEarlyExit
///   - Structure: is_infinite_loop && has_break && has_continue
///
/// - Pattern 4: Loop with Continue (loop_continue_pattern4.hako)
///   - Detection: pattern_kind == Pattern4Continue
///   - Structure: has_continue && !has_break
///
/// - Pattern 3: Loop with If-Else PHI (loop_if_phi.hako)
///   - Detection: pattern_kind == Pattern3IfPhi
///   - Structure: has_if_else_phi && !has_break && !has_continue
///
/// - Pattern 1: Simple While Loop (loop_min_while.hako)
///   - Detection: pattern_kind == Pattern1SimpleWhile
///   - Structure: !has_break && !has_continue && !has_if_else_phi
///
/// - Pattern 2: Loop with Conditional Break (joinir_min_loop.hako)
///   - Detection: pattern_kind == Pattern2Break
///   - Structure: has_break && !has_continue
///
/// Note: func_name is now only used for debug logging, not pattern detection
pub(crate) static LOOP_PATTERNS: &[LoopPatternEntry] = &[
    LoopPatternEntry {
        name: "Pattern5_InfiniteEarlyExit",
        detect: super::pattern5_infinite_early_exit::can_lower,
        lower: super::pattern5_infinite_early_exit::lower,
    },
    LoopPatternEntry {
        name: "Pattern4_WithContinue",
        detect: super::pattern4_with_continue::can_lower,
        lower: super::pattern4_with_continue::lower,
    },
    LoopPatternEntry {
        name: "Pattern3_WithIfPhi",
        detect: super::pattern3_with_if_phi::can_lower,
        lower: super::pattern3_with_if_phi::lower,
    },
    LoopPatternEntry {
        name: "Pattern1_Minimal",
        detect: super::pattern1_minimal::can_lower,
        lower: super::pattern1_minimal::lower,
    },
    LoopPatternEntry {
        name: "Pattern2_WithBreak",
        detect: super::pattern2_with_break::can_lower,
        lower: super::pattern2_with_break::lower,
    },
];

/// Try all registered patterns in priority order.
///
/// Returns Ok(Some(value_id)) if a pattern matched and lowered successfully.
/// Returns Ok(None) if no pattern matched.
/// Returns Err if a pattern matched but lowering failed.
///
/// # Phase 183: Structure-based routing
///
/// This router uses the centralized pattern classification system:
/// - Pattern detection: `ctx.pattern_kind` (from `loop_pattern_detection::classify`)
/// - No redundant pattern detection in detect functions
/// - All patterns use structure-based classification
pub(crate) fn route_loop_pattern(
    builder: &mut MirBuilder,
    ctx: &LoopPatternContext,
) -> Result<Option<ValueId>, String> {
    use super::super::trace;

    // Phase 183: Route based on pre-classified pattern kind
    // Pattern kind was already determined by ctx.pattern_kind in LoopPatternContext::new()
    // This eliminates duplicate detection logic across routers.

    // Find matching pattern entry based on pattern_kind
    for entry in LOOP_PATTERNS {
        if (entry.detect)(builder, ctx) {
            // Phase 195: Use unified trace for pattern matching
            trace::trace().pattern("route", entry.name, true);
            return (entry.lower)(builder, ctx);
        }
    }

    // No pattern matched - return None (caller will handle error)
    // Phase 187-2: Legacy LoopBuilder removed, all loops must use JoinIR
    if ctx.debug {
        trace::trace().debug(
            "route",
            &format!(
                "No pattern matched for function '{}' (pattern_kind={:?})",
                ctx.func_name, ctx.pattern_kind
            ),
        );
    }
    Ok(None)
}