//! Grammar coverage matrix for REPL testing

//!

//! Tracks coverage of all grammar productions to ensure complete testing

use crate::frontend::ast::Expr;

use anyhow::Result;

use std::collections::{HashMap, HashSet};

use std::time::Duration;

/// Statistics for a single grammar production

#[derive(Default, Debug)]

pub struct ProductionStats {

    pub hit_count: usize,

    pub success_count: usize,

    pub avg_latency_ns: u64,

    pub error_patterns: Vec<String>,

}

/// Grammar coverage tracking matrix

#[derive(Default)]

pub struct GrammarCoverageMatrix {

    pub productions: HashMap<&'static str, ProductionStats>,

    pub ast_variants: HashSet<String>,

    pub uncovered: Vec<&'static str>,

}

impl GrammarCoverageMatrix {

    /// Create a new coverage matrix

    pub fn new() -> Self {

        Self::default()

    }

    /// Record a parse attempt

    pub fn record(

        &mut self,

        production: &'static str,

        input: &str,

        result: Result<Expr>,

        elapsed: Duration,

    ) {

        let stats = self.productions.entry(production).or_default();

        stats.hit_count += 1;

        let elapsed_ns =

            u64::try_from(elapsed.as_nanos().min(u128::from(u64::MAX))).unwrap_or(u64::MAX);

        stats.avg_latency_ns = if stats.hit_count == 1 {

            elapsed_ns

        } else {

            (stats.avg_latency_ns * (stats.hit_count as u64 - 1) + elapsed_ns)

                / stats.hit_count as u64

        };

        match result {

            Ok(ast) => {

                stats.success_count += 1;

                self.record_ast_variants(&ast);

            }

            Err(e) => {

                let error_msg = format!("{input}: {e}");

                if !stats.error_patterns.contains(&error_msg) {

                    stats.error_patterns.push(error_msg);

                }

            }

        }

    }

    /// Record AST variant usage

    fn record_ast_variants(&mut self, expr: &Expr) {

        use crate::frontend::ast::ExprKind;

        let variant_name = match &expr.kind {

            ExprKind::Literal(_) => "Literal",

            ExprKind::Identifier(_) => "Identifier",

            ExprKind::Binary { .. } => "Binary",

            ExprKind::Unary { .. } => "Unary",

            ExprKind::Call { .. } => "Call",

            ExprKind::MethodCall { .. } => "MethodCall",

            ExprKind::If { .. } => "If",

            ExprKind::Match { .. } => "Match",

            ExprKind::Block(_) => "Block",

            ExprKind::Let { .. } => "Let",

            ExprKind::Function { .. } => "Function",

            ExprKind::Lambda { .. } => "Lambda",

            ExprKind::Throw { .. } => "Throw",

            ExprKind::Ok { .. } => "Ok",

            ExprKind::Err { .. } => "Err",

            ExprKind::While { .. } => "While",

            ExprKind::For { .. } => "For",

            ExprKind::Struct { .. } => "Struct",

            ExprKind::StructLiteral { .. } => "StructLiteral",

            ExprKind::ObjectLiteral { .. } => "ObjectLiteral",

            ExprKind::FieldAccess { .. } => "FieldAccess",

            ExprKind::Trait { .. } => "Trait",

            ExprKind::Impl { .. } => "Impl",

            ExprKind::Extension { .. } => "Extension",

            ExprKind::Await { .. } => "Await",

            ExprKind::List(_) => "List",

            ExprKind::ListComprehension { .. } => "ListComprehension",

            ExprKind::StringInterpolation { .. } => "StringInterpolation",

            ExprKind::QualifiedName { .. } => "QualifiedName",

            ExprKind::Send { .. } => "Send",

            ExprKind::Ask { .. } => "Ask",

            ExprKind::Command { .. } => "Command",

            ExprKind::Macro { .. } => "Macro",

            ExprKind::Actor { .. } => "Actor",

            ExprKind::DataFrame { .. } => "DataFrame",

            ExprKind::DataFrameOperation { .. } => "DataFrameOperation",

            ExprKind::Pipeline { .. } => "Pipeline",

            ExprKind::Import { .. } => "Import",

            ExprKind::Export { .. } => "Export",

            ExprKind::Module { .. } => "Module",

            ExprKind::Range { .. } => "Range",

            ExprKind::Break { .. } => "Break",

            ExprKind::Continue { .. } => "Continue",

            ExprKind::Assign { .. } => "Assign",

            ExprKind::CompoundAssign { .. } => "CompoundAssign",

            _ => "Other",

        };

        self.ast_variants.insert(variant_name.to_string());

    }

    /// Check if coverage is complete

    pub fn is_complete(&self, required_productions: usize) -> bool {

        self.productions.len() >= required_productions && self.uncovered.is_empty()

    }

    /// Assert that coverage is complete

    ///

    /// # Panics

    ///

    /// Panics if there are uncovered productions or if the number of covered

    /// productions is less than the required amount.

    pub fn assert_complete(&self, required_productions: usize) {

        assert!(

            self.uncovered.is_empty(),

            "Uncovered productions: {:?}",

            self.uncovered

        );

        assert!(

            self.productions.len() >= required_productions,

            "Only {} of {} productions covered",

            self.productions.len(),

            required_productions

        );

    }

    /// Generate a coverage report

    pub fn report(&self) -> String {

        use std::fmt::Write;

        let mut report = String::new();

        report.push_str("Grammar Coverage Report\n");

        report.push_str("=======================\n\n");

        let _ = writeln!(

            &mut report,

            "Productions covered: {}",

            self.productions.len()

        );

        let _ = writeln!(

            &mut report,

            "AST variants seen: {}",

            self.ast_variants.len()

        );

        let total_hits: usize = self.productions.values().map(|s| s.hit_count).sum();

        let total_success: usize = self.productions.values().map(|s| s.success_count).sum();

        let _ = writeln!(&mut report, "Total attempts: {total_hits}");

        let success_rate = if total_hits > 0 {

            #[allow(clippy::cast_precision_loss)]

            let rate = (total_success as f64 / total_hits as f64) * 100.0;

            rate

        } else {

            0.0

        };

        let _ = writeln!(&mut report, "Success rate: {success_rate:.2}%");

        // Find slowest productions

        let mut slowest: Vec<_> = self.productions.iter().collect();

        slowest.sort_by_key(|(_, stats)| stats.avg_latency_ns);

        slowest.reverse();

        if !slowest.is_empty() {

            report.push_str("\nSlowest productions:\n");

            for (name, stats) in slowest.iter().take(5) {

                #[allow(clippy::cast_precision_loss)]

                let ms = stats.avg_latency_ns as f64 / 1_000_000.0;

                let _ = writeln!(&mut report, "  {name}: {ms:.2}ms");

            }

        }

        if !self.uncovered.is_empty() {

            report.push_str("\nUncovered productions:\n");

            for prod in &self.uncovered {

                let _ = writeln!(&mut report, "  - {prod}");

            }

        }

        report

    }

}

/// All grammar productions that need coverage

pub const GRAMMAR_PRODUCTIONS: &[(&str, &str)] = &[

    // Core literals (5)

    ("literal_int", "42"),

    ("literal_float", "3.14"),

    ("literal_string", r#""hello""#),

    ("literal_bool", "true"),

    ("literal_unit", "()"),

    // Binary operators (12)

    ("op_assign", "x = 5"),

    ("op_logical_or", "a || b"),

    ("op_logical_and", "a && b"),

    ("op_equality", "x == y"),

    ("op_comparison", "x < y"),

    ("op_bitwise_or", "a | b"),

    ("op_bitwise_xor", "a ^ b"),

    ("op_bitwise_and", "a & b"),

    ("op_shift", "x << 2"),

    ("op_range", "0..10"),

    ("op_add", "x + y"),

    ("op_mul", "x * y"),

    // Unary operators (3)

    ("op_neg", "-x"),

    ("op_not", "!x"),

    ("op_ref", "&value"),

    // Control flow (5)

    ("if_expr", "if x > 0 { 1 } else { -1 }"),

    ("match_expr", "match x { Some(y) => y, None => 0 }"),

    ("for_loop", "for x in 0..10 { print(x) }"),

    ("while_loop", "while x > 0 { x = x - 1 }"),

    ("loop_expr", "loop { break 42 }"),

    // Function calls (5) - CRITICAL: These were missing!

    ("call_simple", "println(42)"),

    ("call_args", "println(\"Hello\", \"World\")"),

    ("call_expr", "add(2 + 3, 4 * 5)"),

    ("call_nested", "println(add(1, 2))"),

    ("call_builtin", "print(\"test\")"),

    // Functions (4)

    ("fun_decl", "fun add(a: Int, b: Int) -> Int { a + b }"),

    ("fun_generic", "fun id<T>(x: T) -> T { x }"),

    ("lambda", "|x| x * 2"),

    ("lambda_typed", "|x: Int| -> Int { x * 2 }"),

    // Pattern matching (6)

    ("pattern_bind", "let x = 5"),

    ("pattern_tuple", "let (x, y) = (1, 2)"),

    ("pattern_struct", "let Point { x, y } = p"),

    ("pattern_enum", "let Some(x) = opt"),

    ("pattern_slice", "let [head, ..tail] = list"),

    ("pattern_guard", "match x { n if n > 0 => n }"),

    // Type system (5)

    ("type_simple", "let x: Int = 5"),

    ("type_generic", "let v: Vec<Int> = vec![1,2,3]"),

    ("type_function", "let f: Fn(Int) -> Int = |x| x"),

    ("type_tuple", "let t: (Int, String) = (1, \"hi\")"),

    ("type_option", "let opt: Option<Int> = Some(5)"),

    // Structs/Traits/Impls (3)

    ("struct_decl", "struct Point { x: Float, y: Float }"),

    ("trait_decl", "trait Show { fun show(self) -> String }"),

    (

        "impl_block",

        "impl Show for Point { fun show(self) -> String { \"...\" } }",

    ),

    // Actor system (4)

    ("actor_decl", "actor Counter { state count: Int = 0 }"),

    ("actor_handler", "on Increment { self.count += 1 }"),

    ("send_op", "counter <- Increment"),

    ("ask_op", "let n = counter <? GetCount"),

    // DataFrame operations (6)

    ("df_literal", "df![a = [1,2,3], b = [4,5,6]]"),

    ("df_filter", "df >> filter(col(\"age\") > 18)"),

    ("df_select", "df >> select([\"name\", \"age\"])"),

    ("df_groupby", "df >> groupby(\"dept\")"),

    ("df_agg", "df >> agg([mean(\"salary\"), count()])"),

    ("df_join", "df1 >> join(df2, on: \"id\")"),

    // Pipeline operators (3)

    ("pipe_simple", "data >> filter(|x| x > 0)"),

    ("pipe_method", "text >> trim() >> uppercase()"),

    ("pipe_nested", "x >> (|y| y >> double() >> square())"),

    // String interpolation (2)

    ("string_interp", r#"f"Hello {name}""#),

    ("string_complex", r#"f"Result: {compute(x):.2f}""#),

    // Import/Export (3)

    ("import_simple", "import std::fs"),

    (

        "import_multi",

        "import std::collections::{HashMap, HashSet}",

    ),

    ("export", "export { Point, distance }"),

    // Macros (2)

    ("macro_println", "println!(\"Hello\", \"World\")"),

    ("macro_vec", "vec![1, 2, 3]"),

];