use core::fmt::{Display, Formatter};

use crate::{

    core::structure::{modules::indices::FuncIdx, types::ValType},

    validation::validation_stack::ValidationStackEntry,

    DecodingError, RefType,

};

#[derive(Debug, PartialEq, Eq, Clone)]

pub enum ValidationError {

    Decoding(DecodingError),

    /// An index for a type is invalid.

    InvalidTypeIdx(u32),

    /// An index for a function is invalid.

    InvalidFuncIdx(u32),

    /// An index for a table is invalid.

    InvalidTableIdx(u32),

    /// An index for a memory is invalid.

    InvalidMemIdx(u32),

    /// An index for a global is invalid.

    InvalidGlobalIdx(u32),

    /// An index for an element segment is invalid.

    InvalidElemIdx(u32),

    /// An index for a data segment is invalid.

    InvalidDataIdx(u32),

    /// An index for a local is invalid.

    InvalidLocalIdx(u32),

    /// An index for a label is invalid.

    InvalidLabelIdx(u32),

    /// An index for a lane of some vector type is invalid.

    InvalidLaneIdx(u8),

    ExprMissingEnd,

    InvalidInstr(u8),

    InvalidMultiByteInstr(u8, u32),

    EndInvalidValueStack,

    InvalidValidationStackValType(Option<ValType>),

    InvalidValidationStackType(ValidationStackEntry),

    ExpectedAnOperand,

    /// An attempt has been made to mutate a const global

    MutationOfConstGlobal,

    /// An alignment of some memory instruction is invalid

    ErroneousAlignment {

        alignment: u32,

        minimum_required_alignment: u32,

    },

    /// The validation control stack is empty, even though an entry was expected.

    // TODO Reconsider if we want to expose this error. It should probably never happen and thus also never bubble up to the user.

    ValidationCtrlStackEmpty,

    /// An `else` instruction was found while not inside an `if` block.

    ElseWithoutMatchingIf,

    /// An `end` for a matching `if` instruction was found, but there was no `else` instruction in between.

    IfWithoutMatchingElse,

    /// A `table.init` instruction specified a table and an element segment that store different reference types.

    MismatchedRefTypesDuringTableInit {

        table_ty: RefType,

        elem_ty: RefType,

    },

    /// A `table.copy` instruction referenced two tables that store different reference types.

    MismatchedRefTypesDuringTableCopy {

        source_table_ty: RefType,

        destination_table_ty: RefType,

    },

    /// An expected reference type did not match the actual reference type on the validation stack.

    MismatchedRefTypesOnValidationStack {

        expected: RefType,

        actual: RefType,

    },

    /// An indirect call to a table with does not store function references was made.

    IndirectCallToNonFuncRefTable(RefType),

    /// A reference type was expected to be on the stack, but a value type was found.

    ExpectedReferenceTypeOnStack(ValType),

    /// When a is referenced in the code section it must be contained in `C.refs`, which was not the case

    ReferencingAnUnreferencedFunction(FuncIdx),

    /// The select instructions may work with multiple values in the future. However, as of now its vector may only have one element.

    InvalidSelectTypeVectorLength(usize),

    /// Multiple exports share the same name

    DuplicateExportName,

    /// Multiple memories are not yet allowed without the proposal.

    UnsupportedMultipleMemoriesProposal,

    /// An expr in the code section has trailing instructions following its `end` instruction.

    CodeExprHasTrailingInstructions,

    /// The lengths of the function and code sections must match.

    FunctionAndCodeSectionsHaveDifferentLengths,

    /// The data count specified in the data count section and the length of the data section must match.

    DataCountAndDataSectionsLengthAreDifferent,

    InvalidImportType,

    /// The function signature of the start function is invalid. It must not specify any parameters or return values.

    InvalidStartFunctionSignature,

    /// An active element segment's type and its table's type are different.

    ActiveElementSegmentTypeMismatch,

    /// The data count section is required, if there are instructions that use

    /// data indices.

    MissingDataCountSection,

    /// The mode of a data segment was invalid. Only values in the range 0..=2

    /// are allowed.

    InvalidDataSegmentMode(u32),

    /// The mode of an element was invalid. Only values in the range 0..=7 are

    /// allowed.

    InvalidElementMode(u32),

    /// The module contains too many functions, i.e. imported or locally-defined

    /// functions. The maximum number of functions is [`u32::MAX`].

    TooManyFunctions,

    /// The module contains too many tables, i.e. imported or locally-defined

    /// tables. The maximum number of tables is [`u32::MAX`].

    TooManyTables,

    /// The module contains too many memories, i.e. imported or locally-defined

    /// memories. The maximum number of memories is [`u32::MAX`].

    TooManyMemories,

    /// The module contains too many globals, i.e. imported or locally-defined

    /// globals. The maximum number of memories is [`u32::MAX`].

    TooManyGlobals,

    /// The min field of a limits type is larger than the max field.

    LimitsMinLargerThanMax {

        min: u32,

        max: u32,

    },

    /// The min or max field of a limits type is not within the expected range.

    LimitsNotWithinRange(u32),

    /// A mutable global was referenced in some global.get instruction in a constant expression.

    MutGlobalInConstGlobalGet,

}

impl core::error::Error for ValidationError {}

impl Display for ValidationError {

    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {

        match self {

            ValidationError::Decoding(err) => write!(f, "Decoding failed: {err}"),

            ValidationError::InvalidTypeIdx(idx) => write!(f, "The type index {idx} is invalid"),

            ValidationError::InvalidFuncIdx(idx) => write!(f, "The function index {idx} is invalid"),

            ValidationError::InvalidTableIdx(idx) => write!(f, "The table index {idx} is invalid"),

            ValidationError::InvalidMemIdx(idx) => write!(f, "The memory index {idx} is invalid"),

            ValidationError::InvalidGlobalIdx(idx) => write!(f, "The global index {idx} is invalid"),

            ValidationError::InvalidElemIdx(idx) => write!(f, "The element segment index {idx} is invalid"),

            ValidationError::InvalidDataIdx(idx) => write!(f, "The data segment index {idx} is invalid"),

            ValidationError::InvalidLocalIdx(idx) => write!(f, "The local index {idx} is invalid"),

            ValidationError::InvalidLabelIdx(idx) => write!(f, "The label index {idx} is invalid"),

            ValidationError::InvalidLaneIdx(idx) => write!(f, "The lane index {idx} is invalid"),

            ValidationError::ExprMissingEnd => write!(f, "An expr type is missing an end byte"),

            ValidationError::InvalidInstr(byte) => write!(f, "The instruction {byte:#x} is invalid"),

            ValidationError::InvalidMultiByteInstr(first_byte, second_instr) => write!(f, "The multi-byte instruction {first_byte:#x} {second_instr} is invalid"),

            ValidationError::ActiveElementSegmentTypeMismatch => write!(f, "an element segment's type and its table's type are different"),

            ValidationError::EndInvalidValueStack => write!(f, "Different value stack types were expected at the end of a block/function"),

            ValidationError::InvalidValidationStackValType(ty) => write!(f, "An unexpected type `{ty:?}` was found on the stack when trying to pop another"),

            ValidationError::InvalidValidationStackType(ty) => write!(f, "An unexpected type `{ty:?}` was found on the stack"),

            ValidationError::ExpectedAnOperand => write!(f, "Expected a value type operand on the stack"),

            ValidationError::MutationOfConstGlobal => write!(f, "An attempt has been made to mutate a const global"),

            ValidationError::ErroneousAlignment {alignment , minimum_required_alignment} => write!(f, "The alignment 2^{alignment} is not less or equal to the required alignment 2^{minimum_required_alignment}"),

            ValidationError::ValidationCtrlStackEmpty => write!(f, "Failed to retrieve last ctrl block because validation ctrl stack is empty"),

            ValidationError::ElseWithoutMatchingIf => write!(f, "Found `else` without a previous matching `if` instruction"),

            ValidationError::IfWithoutMatchingElse => write!(f, "Found `end` without a previous matching `else` to an `if` instruction"),

            ValidationError::MismatchedRefTypesDuringTableInit { table_ty, elem_ty } => write!(f, "Mismatch of table type `{table_ty:?}` and element segment type `{elem_ty:?}` for `table.init` instruction"),

            ValidationError::MismatchedRefTypesDuringTableCopy { source_table_ty, destination_table_ty } => write!(f, "Mismatch of source table type `{source_table_ty:?}` and destination table type `{destination_table_ty:?}` for `table.copy` instruction"),

            ValidationError::MismatchedRefTypesOnValidationStack { expected, actual } => write!(f, "Mismatch of reference types on the value stack: Expected `{expected:?}` but got `{actual:?}`"),

            ValidationError::IndirectCallToNonFuncRefTable(table_ty) => write!(f, "An indirect call to a table which does not store function references but instead `{table_ty:?}` was made"),

            ValidationError::ExpectedReferenceTypeOnStack(found_valtype) => write!(f, "Expected a reference type but instead found a `{found_valtype:?}` on the stack"),

            ValidationError::ReferencingAnUnreferencedFunction(func_idx) => write!(f, "Referenced a function with index {func_idx} that was not referenced in prior validation"),

            ValidationError::InvalidSelectTypeVectorLength(len) => write!(f, "The type vector of a `select` instruction must be of length 1 as of now but it is of length {len} instead"),

            ValidationError::DuplicateExportName => write!(f,"Multiple exports share the same name"),

            ValidationError::UnsupportedMultipleMemoriesProposal => write!(f,"A memory index other than 1 was used, but the proposal for multiple memories is not yet supported"),

            ValidationError::CodeExprHasTrailingInstructions => write!(f,"A code expression has invalid trailing instructions following its `end` instruction"),

            ValidationError::FunctionAndCodeSectionsHaveDifferentLengths => write!(f,"The function and code sections have different lengths"),

            ValidationError::DataCountAndDataSectionsLengthAreDifferent => write!(f,"The data count section specifies a different length than there are data segments in the data section"),

            ValidationError::InvalidImportType => f.write_str("Invalid import type"),

            ValidationError::InvalidStartFunctionSignature => write!(f,"The start function has parameters or return types which it is not allowed to have"),

            ValidationError::MissingDataCountSection => f.write_str("Some instructions could not be validated because the data count section is missing"),

            ValidationError::InvalidDataSegmentMode(mode) => write!(f, "The mode of a data segment was invalid (only 0..=2 is allowed): {mode}"),

            ValidationError::InvalidElementMode(mode) => write!(f, "The mode of an element was invalid (only 0..=7 is allowed): {mode}"),

            ValidationError::TooManyFunctions => f.write_str("The module contains too many functions. The maximum number of functions (either imported or locally-defined) is 2^32 - 1"),

            ValidationError::TooManyTables => f.write_str("The module contains too many tables. The maximum number of tables (either imported or locally-defined) is 2^32 - 1"),

            ValidationError::TooManyMemories => f.write_str("The module contains too many memories. The maximum number of memories (either imported or locally-defined) is 2^32 - 1"),

            ValidationError::TooManyGlobals => f.write_str("The module contains too many globals. The maximum number of globals (either imported or locally-defined) is 2^32 - 1"),

            ValidationError::LimitsMinLargerThanMax { min, max } => write!(f, "Limits are invalid because min={min} is larger than max={max}"),

            ValidationError::LimitsNotWithinRange(range) => write!(f, "The min or max field of a limits type is not within the expected range of {range}"),

            ValidationError::MutGlobalInConstGlobalGet => f.write_str("A mutable global was referenced in some global.get instruction in a constant expression"),

        }

    }

}

impl ValidationError {

    /// Convert this error to a message that is compatible with the error messages used by the official Wasm testsuite.

    pub fn to_message(&self) -> &'static str {

        todo!("convert validation error to testsuite message");

    }

}

impl From<DecodingError> for ValidationError {

    fn from(error: DecodingError) -> Self {

        Self::Decoding(error)

    }

}

#[cfg(test)]

mod test {

    use alloc::string::ToString;

    use crate::core::decoding::error::DecodingError;

    #[test]

    fn fmt_invalid_magic() {

        assert!(DecodingError::InvalidMagic

            .to_string()

            .contains("magic number"));

    }

    #[test]

    fn fmt_invalid_version() {

        assert!(DecodingError::InvalidBinaryFormatVersion

            .to_string()

            .contains("version"));

    }

}