//! Abstract syntax tree node types.

use el_lexer::Span;

// ── Test-specific nodes ───────────────────────────────────────────────────────

/// Which graph a test should execute against.
#[derive(Debug, Clone, PartialEq)]
pub enum TestTarget {
    /// In-memory graph — default, zero external dependencies.
    Unit,
    /// Real Engram database pointed at by `ENGRAM_URL` / `ENGRAM_DB_PATH`.
    E2e,
    /// Run against both unit (in-memory) and e2e (real DB).
    Both,
}

/// A `seed Node { ... }` or `seed Edge { ... }` statement inside a test block.
#[derive(Debug, Clone, PartialEq)]
pub enum SeedStmt {
    Node {
        node_type: String,
        content: String,
        importance: f32,
        tier: Option<String>,
    },
    Edge {
        from: String,
        to: String,
        relation: String,
        weight: f32,
    },
}

// ── Literals ──────────────────────────────────────────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub enum Literal {
    Int(i64),
    Float(f64),
    Str(String),
    Bool(bool),
}

// ── Type expressions ──────────────────────────────────────────────────────────

/// A type annotation in source code, e.g. `String`, `[Int]`, `User?`.
#[derive(Debug, Clone, PartialEq)]
pub enum TypeExpr {
    /// A named type: `Int`, `String`, `User`, …
    Named(String),
    /// An array type: `[T]`
    Array(Box<TypeExpr>),
    /// An optional type: `T?`
    Optional(Box<TypeExpr>),
    /// A function type: `fn(A, B) -> C`
    Fn { params: Vec<TypeExpr>, return_type: Box<TypeExpr> },
    /// `Result<T, E>` — built-in error-propagation type
    Result { ok: Box<TypeExpr>, err: Box<TypeExpr> },
    /// `Map<K, V>` — built-in key-value map type
    Map { key: Box<TypeExpr>, value: Box<TypeExpr> },
    /// A generic type parameter: `T`, `E` — used inside generic function signatures.
    TypeParam(String),
}

// ── Patterns (for match arms) ─────────────────────────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub enum Pattern {
    /// `Status::Active`
    EnumVariant { enum_name: String, variant: String, payload: Option<String> },
    /// A wildcard `_`
    Wildcard,
    /// A literal: `42`, `"str"`, `true`
    Literal(Literal),
    /// A binding: `x`
    Binding(String),
}

// ── Binary operators ──────────────────────────────────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub enum BinOp {
    Add, Sub, Mul, Div,
    Eq, NotEq, Lt, Gt, LtEq, GtEq,
    And, Or,
}

// ── Expressions ───────────────────────────────────────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub enum Expr {
    Literal(Literal),
    Ident(String),
    BinOp { op: BinOp, left: Box<Expr>, right: Box<Expr> },
    UnaryNot(Box<Expr>),
    Call { func: Box<Expr>, args: Vec<Expr> },
    Block(Vec<Stmt>),
    Match { subject: Box<Expr>, arms: Vec<MatchArm> },
    /// `activate TypeName where "semantic query string"`
    Activate { type_name: String, query: String },
    /// `sealed { stmts... }` — quantum-sealed block
    Sealed(Vec<Stmt>),
    If { cond: Box<Expr>, then: Box<Expr>, else_: Option<Box<Expr>> },
    Field { object: Box<Expr>, field: String },
    /// Array constructor: `[a, b, c]`
    Array(Vec<Expr>),
    /// Path expression: `Status::Active` (enum variant ref)
    Path { segments: Vec<String> },
    /// Index expression: `arr[0]`
    Index { object: Box<Expr>, index: Box<Expr> },
    /// Closure: `|x: Int| x * 2` or `|x: Int| -> Int { x * 2 }`
    Closure {
        params: Vec<Param>,
        return_type: Option<TypeExpr>,
        body: Box<Expr>,
        span: Span,
    },
    /// Try operator: `expr?` — unwraps Result, propagates error
    Try(Box<Expr>),
    /// Map literal: `{"key": value, ...}`
    MapLiteral(Vec<(Expr, Expr)>),
    /// Struct literal: `Point { x: 10, y: 20 }`
    StructLit {
        type_name: String,
        fields: Vec<(String, Expr)>,
        span: Span,
    },
    /// Record update: `a with { field: new_val }`
    With {
        base: Box<Expr>,
        updates: Vec<(String, Expr)>,
    },
    /// AI inference: `reason "query"`
    Reason {
        query: String,
    },
    /// Concurrent execution: `parallel { name: expr, ... }`
    Parallel {
        entries: Vec<(String, Expr)>,
    },
    /// Trace block: `trace "label" { stmts }`
    Trace {
        label: String,
        body: Vec<Stmt>,
    },
}

// ── Match arm ─────────────────────────────────────────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub struct MatchArm {
    pub pattern: Pattern,
    pub body: Expr,
    pub span: Span,
}

// ── Decorators ────────────────────────────────────────────────────────────────

/// A decorator applied to a function: `@name` or `@name(args)`
#[derive(Debug, Clone, PartialEq)]
pub struct Decorator {
    pub name: String,
    pub args: Vec<Expr>,
    pub span: Span,
}

// ── Protocol ──────────────────────────────────────────────────────────────────

/// A method signature inside a protocol definition.
#[derive(Debug, Clone, PartialEq)]
pub struct ProtocolMethod {
    pub name: String,
    pub params: Vec<Param>,
    pub return_type: TypeExpr,
    pub span: Span,
}

// ── Statements ────────────────────────────────────────────────────────────────

/// A named parameter in a function definition.
#[derive(Debug, Clone, PartialEq)]
pub struct Param {
    pub name: String,
    pub type_ann: TypeExpr,
    pub span: Span,
}

/// A field in a type definition.
#[derive(Debug, Clone, PartialEq)]
pub struct Field {
    pub name: String,
    pub type_ann: TypeExpr,
    pub span: Span,
}

/// A variant in an enum definition.
#[derive(Debug, Clone, PartialEq)]
pub struct Variant {
    pub name: String,
    /// Payload type, if any (e.g. `Pending(String)`)
    pub payload: Option<TypeExpr>,
    pub span: Span,
}

#[derive(Debug, Clone, PartialEq)]
pub enum Stmt {
    /// `let name: Type = expr`
    Let {
        name: String,
        type_ann: Option<TypeExpr>,
        value: Expr,
        span: Span,
    },
    /// `return expr`
    Return(Expr, Span),
    /// A bare expression used as a statement (usually a call).
    Expr(Expr, Span),
    /// `fn name<T, E>(params) -> ReturnType [requires cond] { body }` (with optional decorators)
    FnDef {
        name: String,
        decorators: Vec<Decorator>,
        /// Generic type parameters, e.g. `["T", "E"]` for `fn foo<T, E>`.
        type_params: Vec<String>,
        params: Vec<Param>,
        return_type: TypeExpr,
        /// Optional precondition: `requires expr`
        requires: Option<Box<Expr>>,
        body: Vec<Stmt>,
        span: Span,
    },
    /// `type Name { fields... }`
    TypeDef {
        name: String,
        fields: Vec<Field>,
        span: Span,
    },
    /// `enum Name { variants... }`
    EnumDef {
        name: String,
        variants: Vec<Variant>,
        span: Span,
    },
    /// `test "name" [target: unit|e2e|both] { body }`
    TestDef {
        name: String,
        target: TestTarget,
        body: Vec<Stmt>,
        span: Span,
    },
    /// `seed Node { ... }` or `seed Edge { ... }`
    Seed(SeedStmt, Span),
    /// `assert <expr>`
    Assert(Expr, Span),
    /// `import std::collections::Map` or `from pkg import { A, B }`
    Import {
        path: Vec<String>,
        names: Vec<String>,
        alias: Option<String>,
        span: Span,
    },
    /// `protocol Name { method sigs... }`
    ProtocolDef {
        name: String,
        methods: Vec<ProtocolMethod>,
        span: Span,
    },
    /// `impl Protocol for TypeName { fn ... }`
    ImplDef {
        protocol_name: String,
        type_name: String,
        methods: Vec<Stmt>,
        span: Span,
    },
    /// `retry N times { ... } fallback { ... }`
    Retry {
        count: Expr,
        body: Vec<Stmt>,
        fallback: Option<Vec<Stmt>>,
        span: Span,
    },
    /// `deploy fn_name to "/route" via target`
    Deploy {
        fn_name: String,
        route: String,
        target: String,
        span: Span,
    },
}

// ── Top-level program ─────────────────────────────────────────────────────────

#[derive(Debug, Clone, PartialEq)]
pub struct Program {
    pub stmts: Vec<Stmt>,
    /// The original source, kept for diagnostics and source maps.
    pub source: String,
}