// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

mod display;
mod params;
mod types;

pub use params::{
    ArrayCreateParams, BuiltinCallParams, ChainedIndexParams, ComprehensionBeginParams,
    FunctionCallParams, InstructionData, LoopStartParams, ObjectCreateParams, SetCreateParams,
    VirtualDataDocumentLookupParams,
};
pub use types::{ComprehensionMode, LiteralOrRegister, LoopMode};

use serde::{Deserialize, Serialize};

/// RVM Instructions - simplified enum-based design
#[repr(C)]
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum Instruction {
    /// Load literal value from literal table into register
    Load {
        dest: u8,
        literal_idx: u16,
    },

    /// Load true value into register
    LoadTrue {
        dest: u8,
    },

    /// Load false value into register
    LoadFalse {
        dest: u8,
    },

    /// Load null value into register
    LoadNull {
        dest: u8,
    },

    /// Load boolean value into register
    LoadBool {
        dest: u8,
        value: bool,
    },

    /// Load global data object into register
    LoadData {
        dest: u8,
    },

    /// Load global input object into register
    LoadInput {
        dest: u8,
    },

    /// Move value from one register to another
    Move {
        dest: u8,
        src: u8,
    },

    /// Arithmetic operations
    Add {
        dest: u8,
        left: u8,
        right: u8,
    },
    Sub {
        dest: u8,
        left: u8,
        right: u8,
    },
    Mul {
        dest: u8,
        left: u8,
        right: u8,
    },
    Div {
        dest: u8,
        left: u8,
        right: u8,
    },
    Mod {
        dest: u8,
        left: u8,
        right: u8,
    },

    /// Comparison operations
    Eq {
        dest: u8,
        left: u8,
        right: u8,
    },
    Ne {
        dest: u8,
        left: u8,
        right: u8,
    },
    Lt {
        dest: u8,
        left: u8,
        right: u8,
    },
    Le {
        dest: u8,
        left: u8,
        right: u8,
    },
    Gt {
        dest: u8,
        left: u8,
        right: u8,
    },
    Ge {
        dest: u8,
        left: u8,
        right: u8,
    },

    /// Logical operations
    And {
        dest: u8,
        left: u8,
        right: u8,
    },
    Or {
        dest: u8,
        left: u8,
        right: u8,
    },
    Not {
        dest: u8,
        operand: u8,
    },

    /// Builtin function calls - optimized for builtin functions
    BuiltinCall {
        /// Index into program's instruction_data.builtin_call_params table
        params_index: u16,
    },

    /// Suspend execution and yield control to the host
    HostAwait {
        /// Destination register to store the resume value
        dest: u8,
        /// Register containing the value to pass to the host
        arg: u8,
        /// Register containing a unique identifier for this await site
        id: u8,
    },

    /// Function rule calls - for user-defined function rules
    FunctionCall {
        /// Index into program's instruction_data.function_call_params table
        params_index: u16,
    },

    /// Return result
    Return {
        value: u8,
    },

    /// Set object field
    ObjectSet {
        obj: u8,
        key: u8,
        value: u8,
    },

    /// Create object with optimized field setting - uses parameter table
    ObjectCreate {
        /// Index into program's instruction_data.object_create_params table
        params_index: u16,
    },

    /// Index into container (object, array, set)
    Index {
        dest: u8,
        container: u8,
        key: u8,
    },

    /// Index into container using literal key (optimization for Load + Index)
    IndexLiteral {
        dest: u8,
        container: u8,
        literal_idx: u16,
    },

    /// Multi-level chained indexing (e.g., obj.field1[expr].field2)
    ChainedIndex {
        /// Index into program's instruction_data.chained_index_params table
        params_index: u16,
    },

    /// Create empty array
    ArrayNew {
        dest: u8,
    },

    /// Push element to array
    ArrayPush {
        arr: u8,
        value: u8,
    },

    /// Create array from registers - returns undefined if any element is undefined
    ArrayCreate {
        /// Index into program's instruction_data.array_create_params table
        params_index: u16,
    },

    /// Create empty set
    SetNew {
        dest: u8,
    },

    /// Add element to set
    SetAdd {
        set: u8,
        value: u8,
    },

    /// Create set from registers - returns undefined if any element is undefined
    SetCreate {
        /// Index into program's instruction_data.set_create_params table
        params_index: u16,
    },

    /// Check if collection contains value (for membership testing)
    Contains {
        dest: u8,
        collection: u8,
        value: u8,
    },

    /// Get count/length of collection (arrays, objects, sets) - returns undefined for non-collections
    Count {
        dest: u8,
        collection: u8,
    },

    /// Assert condition - if register contains false or undefined, return undefined immediately
    AssertCondition {
        condition: u8,
    },

    /// Assert not undefined - if register contains undefined, return undefined immediately
    AssertNotUndefined {
        register: u8,
    },

    /// Start a loop over a collection with specified semantics - uses parameter table
    LoopStart {
        /// Index into program's instruction_data.loop_params table
        params_index: u16,
    },

    /// Continue to next iteration or exit loop
    LoopNext {
        /// Jump target back to loop body
        body_start: u16,
        /// Jump target for loop end
        loop_end: u16,
    },

    /// Call rule with caching - checks cache first, executes rule if needed, supports call stack
    CallRule {
        /// Destination register to store the result of the rule call
        dest: u8,
        /// Rule index to execute
        rule_index: u16,
    },

    /// Initialize a rule
    RuleInit {
        /// The register where rule's result is accumulated.
        result_reg: u8,

        /// The rule number of the rule
        rule_index: u16,
    },

    /// Lookup in data namespace virtual documents (rules + base data)
    VirtualDataDocumentLookup {
        /// Index into program's instruction_data.virtual_data_document_lookup_params table
        params_index: u16,
    },

    /// Mark successful completion of parameter destructuring validation
    DestructuringSuccess {},

    /// Return from rule execution
    RuleReturn {},

    /// Stop execution
    Halt {},

    /// Begin a comprehension with specified parameters
    ComprehensionBegin {
        /// Index into program's instruction_data.comprehension_begin_params table
        params_index: u16,
    },

    /// Yield a value to the current comprehension result
    ComprehensionYield {
        /// Register containing the value to yield to the comprehension
        value_reg: u8,
        /// Optional register containing the key for object comprehensions
        key_reg: Option<u8>,
    },

    /// End a comprehension block
    ComprehensionEnd {},
}

impl Instruction {
    /// Create a new LoopStart instruction with parameter table index
    pub fn loop_start(params_index: u16) -> Self {
        Self::LoopStart { params_index }
    }

    /// Create a new BuiltinCall instruction with parameter table index
    pub fn builtin_call(params_index: u16) -> Self {
        Self::BuiltinCall { params_index }
    }

    /// Create a new HostAwait instruction
    pub fn host_await(dest: u8, arg: u8, id: u8) -> Self {
        Self::HostAwait { dest, arg, id }
    }

    /// Create a new FunctionCall instruction with parameter table index
    pub fn function_call(params_index: u16) -> Self {
        Self::FunctionCall { params_index }
    }

    /// Create a new ObjectCreate instruction with parameter table index
    pub fn object_create(params_index: u16) -> Self {
        Self::ObjectCreate { params_index }
    }

    /// Create a new ArrayCreate instruction with parameter table index
    pub fn array_create(params_index: u16) -> Self {
        Self::ArrayCreate { params_index }
    }

    /// Create a new SetCreate instruction with parameter table index
    pub fn set_create(params_index: u16) -> Self {
        Self::SetCreate { params_index }
    }

    /// Create a new ComprehensionBegin instruction with parameter table index
    pub fn comprehension_begin(params_index: u16) -> Self {
        Self::ComprehensionBegin { params_index }
    }

    /// Create a new ComprehensionYield instruction
    pub fn comprehension_yield(value_reg: u8) -> Self {
        Self::ComprehensionYield {
            value_reg,
            key_reg: None,
        }
    }

    /// Create a new ComprehensionYield instruction for object comprehensions
    pub fn comprehension_yield_object(key_reg: u8, value_reg: u8) -> Self {
        Self::ComprehensionYield {
            value_reg,
            key_reg: Some(key_reg),
        }
    }

    /// Create a new ComprehensionEnd instruction
    pub fn comprehension_end() -> Self {
        Self::ComprehensionEnd {}
    }
}