use std::fmt;

use crate::common::*;
use crate::dbi::Module;
use crate::msf::Stream;
use crate::symbol::SymbolIter;
use crate::FallibleIterator;

mod c13;
mod constants;

pub use c13::{
    CrossModuleExportIter, CrossModuleExports, CrossModuleImports, Inlinee, InlineeIterator,
    InlineeLineIterator,
};

#[derive(Clone, Copy, Debug)]
enum LinesSize {
    C11(usize),
    C13(usize),
}

/// This struct contains data about a single module from its module info stream.
///
/// The module info stream is where private symbols and line info is stored.
pub struct ModuleInfo<'s> {
    stream: Stream<'s>,
    symbols_size: usize,
    lines_size: LinesSize,
}

impl<'s> ModuleInfo<'s> {
    /// Parses a `ModuleInfo` from it's Module info stream data.
    pub(crate) fn parse(stream: Stream<'s>, module: &Module<'_>) -> Self {
        let info = module.info();

        let lines_size = if info.lines_size > 0 {
            LinesSize::C11(info.lines_size as usize)
        } else {
            LinesSize::C13(info.c13_lines_size as usize)
        };

        let symbols_size = info.symbols_size as usize;
        ModuleInfo {
            stream,
            symbols_size,
            lines_size,
        }
    }

    fn lines_data(&self, size: usize) -> &[u8] {
        let start = self.symbols_size as usize;
        &self.stream[start..start + size]
    }

    /// Get an iterator over the all symbols in this module.
    pub fn symbols(&self) -> Result<SymbolIter<'_>> {
        let mut buf = self.stream.parse_buffer();
        buf.truncate(self.symbols_size)?;
        if self.symbols_size > 0 {
            let sig = buf.parse_u32()?;
            if sig != constants::CV_SIGNATURE_C13 {
                return Err(Error::UnimplementedFeature(
                    "Unsupported symbol data format",
                ));
            }
        }
        Ok(SymbolIter::new(buf))
    }

    /// Get an iterator over symbols starting at the given index.
    pub fn symbols_at(&self, index: SymbolIndex) -> Result<SymbolIter<'_>> {
        let mut iter = self.symbols()?;
        iter.seek(index);
        Ok(iter)
    }

    /// Returns a line program that gives access to file and line information in this module.
    pub fn line_program(&self) -> Result<LineProgram<'_>> {
        let inner = match self.lines_size {
            LinesSize::C11(_size) => return Err(Error::UnimplementedFeature("C11 line programs")),
            LinesSize::C13(size) => {
                LineProgramInner::C13(c13::LineProgram::parse(self.lines_data(size))?)
            }
        };

        Ok(LineProgram { inner })
    }

    /// Returns an iterator over all inlinees in this module.
    ///
    /// Inlinees are not guaranteed to be sorted. When requiring random access by `ItemId`, collect
    /// them into a mapping structure rather than reiterating multiple times.
    pub fn inlinees(&self) -> Result<InlineeIterator<'_>> {
        Ok(match self.lines_size {
            // C11 does not contain inlinee information.
            LinesSize::C11(_size) => Default::default(),
            LinesSize::C13(size) => InlineeIterator::parse(self.lines_data(size))?,
        })
    }

    /// Returns a table of exports declared by this module.
    pub fn exports(&self) -> Result<CrossModuleExports> {
        Ok(match self.lines_size {
            // C11 does not have cross module exports.
            LinesSize::C11(_size) => Default::default(),
            LinesSize::C13(size) => CrossModuleExports::parse(self.lines_data(size))?,
        })
    }

    /// Returns a table of imports of this module.
    pub fn imports(&self) -> Result<CrossModuleImports<'_>> {
        Ok(match self.lines_size {
            // C11 does not have cross module imports.
            LinesSize::C11(_size) => Default::default(),
            LinesSize::C13(size) => CrossModuleImports::parse(self.lines_data(size))?,
        })
    }
}

/// Checksum of a source file's contents.
#[derive(Clone, Debug)]
#[allow(missing_docs)]
pub enum FileChecksum<'a> {
    None,
    Md5(&'a [u8]),
    Sha1(&'a [u8]),
    Sha256(&'a [u8]),
}

impl PartialEq for FileChecksum<'_> {
    fn eq(&self, other: &Self) -> bool {
        // Manual implementation to allow for None != None.
        match (self, other) {
            (&FileChecksum::Md5(lhs), &FileChecksum::Md5(rhs)) => lhs == rhs,
            (&FileChecksum::Sha1(lhs), &FileChecksum::Sha1(rhs)) => lhs == rhs,
            (&FileChecksum::Sha256(lhs), &FileChecksum::Sha256(rhs)) => lhs == rhs,
            _ => false,
        }
    }
}

/// Information record on a source file.
#[derive(Clone, Debug, PartialEq)]
pub struct FileInfo<'a> {
    /// Reference to the file name in the [`StringTable`](crate::StringTable).
    pub name: StringRef,

    /// Checksum of the file contents.
    pub checksum: FileChecksum<'a>,
}

/// The kind of source construct a line info is referring to.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum LineInfoKind {
    /// A source code expression.
    Expression,
    /// A source code statement.
    Statement,
}

impl Default for LineInfoKind {
    fn default() -> Self {
        Self::Statement
    }
}

/// Mapping of a source code offset to a source file location.
///
/// A line entry is always valid up to the subsequent entry.
#[derive(Clone, Debug, PartialEq)]
pub struct LineInfo {
    /// Source code offset.
    pub offset: PdbInternalSectionOffset,
    /// The optional length of the code.
    pub length: Option<u32>,
    /// Index of the source file in this module.
    pub file_index: FileIndex,
    /// Line number of the start of the covered range.
    pub line_start: u32,
    /// Line number of the end of the covered range.
    pub line_end: u32,
    /// Column number of the start of the covered range.
    ///
    /// This value is only present if column information is provided by the PDB. Even then, it is
    /// often zero.
    pub column_start: Option<u32>,
    /// Column number of the end of the covered range.
    ///
    /// This value is only present if column information is provided by the PDB. Even then, it is
    /// often zero.
    pub column_end: Option<u32>,
    /// Kind of this line information.
    pub kind: LineInfoKind,
}

impl LineInfo {
    pub(crate) fn set_end(&mut self, end_offset: PdbInternalSectionOffset) {
        // This uses PartialOrd which only compares if the section is equal
        debug_assert!(self.offset <= end_offset);

        if self.offset <= end_offset {
            let length = end_offset.offset - self.offset.offset;
            if self.length.map_or(true, |l| l > length) {
                self.length = Some(length);
            }
        }
    }
}

enum LineProgramInner<'a> {
    C13(c13::LineProgram<'a>),
}

/// The `LineProgram` provides access to source line information for a module and its procedures.
pub struct LineProgram<'a> {
    inner: LineProgramInner<'a>,
}

impl<'a> LineProgram<'a> {
    /// Returns an iterator over all line information records of this module.
    ///
    /// Note that line records are not guaranteed to be ordered by source code offset. If a
    /// monotonic order by `PdbInternalSectionOffset` or `Rva` is required, the lines have to be
    /// sorted manually.
    pub fn lines(&self) -> LineIterator<'_> {
        match self.inner {
            LineProgramInner::C13(ref inner) => LineIterator {
                inner: LineIteratorInner::C13(inner.lines()),
            },
        }
    }

    /// Returns an iterator over all file records of this module.
    pub fn files(&self) -> FileIterator<'a> {
        match self.inner {
            LineProgramInner::C13(ref inner) => FileIterator {
                inner: FileIteratorInner::C13(inner.files()),
            },
        }
    }

    /// Returns an iterator over line records for a symbol at the given section offset.
    ///
    /// This may return line records before the start offset of the symbol. When using ASM,
    /// specifically MASM, symbol records may specify a range that is smaller than the actual
    /// code generated for this function. `lines_for_symbol` returns all line records covering this
    /// function, potentially exceeding this range.
    ///
    /// Note that line records are not guaranteed to be ordered by source code offset. If a
    /// monotonic order by `PdbInternalSectionOffset` or `Rva` is required, the lines have to be
    /// sorted manually.
    pub fn lines_for_symbol(&self, offset: PdbInternalSectionOffset) -> LineIterator<'_> {
        match self.inner {
            LineProgramInner::C13(ref inner) => LineIterator {
                inner: LineIteratorInner::C13(inner.lines_for_symbol(offset)),
            },
        }
    }

    /// Looks up file information for the specified file.
    pub fn get_file_info(&self, offset: FileIndex) -> Result<FileInfo<'a>> {
        match self.inner {
            LineProgramInner::C13(ref inner) => inner.get_file_info(offset),
        }
    }
}

#[derive(Clone, Debug)]
enum LineIteratorInner<'a> {
    C13(c13::LineIterator<'a>),
}

/// An iterator over line information records in a module.
#[derive(Clone, Debug)]
pub struct LineIterator<'a> {
    inner: LineIteratorInner<'a>,
}

impl Default for LineIterator<'_> {
    fn default() -> Self {
        LineIterator {
            inner: LineIteratorInner::C13(Default::default()),
        }
    }
}

impl<'a> FallibleIterator for LineIterator<'a> {
    type Item = LineInfo;
    type Error = Error;

    fn next(&mut self) -> Result<Option<Self::Item>> {
        match self.inner {
            LineIteratorInner::C13(ref mut inner) => inner.next(),
        }
    }
}

#[derive(Clone, Debug)]
enum FileIteratorInner<'a> {
    C13(c13::FileIterator<'a>),
}

/// An iterator over file records in a module.
#[derive(Clone, Debug)]
pub struct FileIterator<'a> {
    inner: FileIteratorInner<'a>,
}

impl Default for FileIterator<'_> {
    fn default() -> Self {
        FileIterator {
            inner: FileIteratorInner::C13(Default::default()),
        }
    }
}

impl<'a> FallibleIterator for FileIterator<'a> {
    type Item = FileInfo<'a>;
    type Error = Error;

    fn next(&mut self) -> Result<Option<Self::Item>> {
        match self.inner {
            FileIteratorInner::C13(ref mut inner) => inner.next(),
        }
    }
}

/// Named reference to a [`Module`].
///
/// The name stored in the [`StringTable`](crate::StringTable) corresponds to the name of the module
/// as returned by [`Module::module_name`].
#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct ModuleRef(pub StringRef);

impl fmt::Display for ModuleRef {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

/// Reference to a local type or id in another module.
///
/// See [`ItemIndex::is_cross_module`] for more information.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct CrossModuleRef<I: ItemIndex>(pub ModuleRef, pub Local<I>);

/// A cross module export that can either be a `Type` or an `Id`.
///
/// Other modules may reference this item using its local ID by declaring it in the cross module
/// imports subsection.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum CrossModuleExport {
    /// A cross module export of a [`Type`](crate::Type).
    Type(Local<TypeIndex>, TypeIndex),
    /// A cross module export of an [`Id`](crate::Id).
    Id(Local<IdIndex>, IdIndex),
}