//! Tokens are what AFL calls extras or dictionaries.
//! They may be inserted as part of mutations during fuzzing.
use alloc::vec::Vec;
#[cfg(any(target_os = "linux", target_vendor = "apple"))]
use core::slice::from_raw_parts;
use core::{
    mem::size_of,
    ops::{Add, AddAssign},
    slice::Iter,
};
#[cfg(feature = "std")]
use std::{
    fs::File,
    io::{BufRead, BufReader},
    path::Path,
};

use hashbrown::HashSet;
use serde::{Deserialize, Serialize};

#[cfg(feature = "std")]
use crate::mutators::str_decode;
use crate::{
    bolts::{rands::Rand, AsSlice},
    inputs::{HasBytesVec, UsesInput},
    mutators::{buffer_self_copy, mutations::buffer_copy, MutationResult, Mutator, Named},
    observers::cmp::{CmpValues, CmpValuesMetadata},
    state::{HasMaxSize, HasMetadata, HasRand},
    Error,
};

/// A state metadata holding a list of tokens
#[derive(Debug, Default, Clone, Serialize, Deserialize)]
#[allow(clippy::unsafe_derive_deserialize)]
pub struct Tokens {
    // We keep a vec and a set, set for faster deduplication, vec for access
    tokens_vec: Vec<Vec<u8>>,
    tokens_set: HashSet<Vec<u8>>,
}

crate::impl_serdeany!(Tokens);

/// The metadata used for token mutators
impl Tokens {
    /// Creates a new tokens metadata (old-skool afl name: `dictornary`)
    #[must_use]
    pub fn new() -> Self {
        Self {
            ..Tokens::default()
        }
    }

    /// Add tokens from a slice of Vecs of bytes
    pub fn add_tokens<IT, V>(&mut self, tokens: IT) -> &mut Self
    where
        IT: IntoIterator<Item = V>,
        V: AsRef<Vec<u8>>,
    {
        for token in tokens {
            self.add_token(token.as_ref());
        }
        self
    }

    /// Build tokens from files
    #[cfg(feature = "std")]
    pub fn add_from_files<IT, P>(mut self, files: IT) -> Result<Self, Error>
    where
        IT: IntoIterator<Item = P>,
        P: AsRef<Path>,
    {
        for file in files {
            self.add_from_file(file)?;
        }
        Ok(self)
    }

    /// Parse autodict section
    pub fn parse_autodict(&mut self, slice: &[u8], size: usize) {
        let mut head = 0;
        loop {
            if head >= size {
                // Sanity Check
                assert!(head == size);
                break;
            }
            let size = slice[head] as usize;
            head += 1;
            if size > 0 {
                self.add_token(&slice[head..head + size].to_vec());
                #[cfg(feature = "std")]
                println!(
                    "Token size: {} content: {:x?}",
                    size,
                    &slice[head..head + size].to_vec()
                );
                head += size;
            }
        }
    }

    /// Create a token section from a start and an end pointer
    /// Reads from an autotokens section, returning the count of new entries read
    ///
    /// # Safety
    /// The caller must ensure that the region between `token_start` and `token_stop`
    /// is a valid region, containing autotokens in the exepcted format.
    #[cfg(any(target_os = "linux", target_vendor = "apple"))]
    pub unsafe fn from_mut_ptrs(
        token_start: *const u8,
        token_stop: *const u8,
    ) -> Result<Self, Error> {
        let mut ret = Self::default();
        if token_start.is_null() || token_stop.is_null() {
            return Ok(Self::new());
        }
        if token_stop < token_start {
            return Err(Error::illegal_argument(format!(
                "Tried to create tokens from illegal section: stop < start ({token_stop:?} < {token_start:?})"
            )));
        }
        let section_size: usize = token_stop.offset_from(token_start).try_into().unwrap();
        // println!("size: {}", section_size);
        let slice = from_raw_parts(token_start, section_size);

        // Now we know the beginning and the end of the token section.. let's parse them into tokens
        ret.parse_autodict(slice, section_size);

        Ok(ret)
    }

    /// Creates a new instance from a file
    #[cfg(feature = "std")]
    pub fn from_file<P>(file: P) -> Result<Self, Error>
    where
        P: AsRef<Path>,
    {
        let mut ret = Self::new();
        ret.add_from_file(file)?;
        Ok(ret)
    }

    /// Adds a token to a dictionary, checking it is not a duplicate
    /// Returns `false` if the token was already present and did not get added.
    #[allow(clippy::ptr_arg)]
    pub fn add_token(&mut self, token: &Vec<u8>) -> bool {
        if !self.tokens_set.insert(token.clone()) {
            return false;
        }
        self.tokens_vec.push(token.clone());
        true
    }

    /// Reads a tokens file, returning the count of new entries read
    #[cfg(feature = "std")]
    pub fn add_from_file<P>(&mut self, file: P) -> Result<&mut Self, Error>
    where
        P: AsRef<Path>,
    {
        // println!("Loading tokens file {:?} ...", file);

        let file = File::open(file)?; // panic if not found
        let reader = BufReader::new(file);

        for line in reader.lines() {
            let line = line.unwrap();
            let line = line.trim_start().trim_end();

            // we are only interested in '"..."', not prefixed 'foo = '
            let start = line.chars().next();
            if line.is_empty() || start == Some('#') {
                continue;
            }
            let Some(pos_quote) = line.find('\"') else { return Err(Error::illegal_argument(format!("Illegal line: {line}"))) };
            if line.chars().nth(line.len() - 1) != Some('"') {
                return Err(Error::illegal_argument(format!("Illegal line: {line}")));
            }

            // extract item
            let Some(item) = line.get(pos_quote + 1..line.len() - 1) else { return Err(Error::illegal_argument(format!("Illegal line: {line}"))) };
            if item.is_empty() {
                continue;
            }

            // decode
            let token: Vec<u8> = match str_decode(item) {
                Ok(val) => val,
                Err(_) => {
                    return Err(Error::illegal_argument(format!(
                        "Illegal line (hex decoding): {line}"
                    )))
                }
            };

            // add
            self.add_token(&token);
        }

        Ok(self)
    }

    /// Returns the amount of tokens in this Tokens instance
    #[inline]
    #[must_use]
    pub fn len(&self) -> usize {
        self.tokens_vec.len()
    }

    /// Returns if this tokens-instance is empty
    #[inline]
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.tokens_vec.is_empty()
    }

    /// Gets the tokens stored in this db
    #[must_use]
    pub fn tokens(&self) -> &[Vec<u8>] {
        &self.tokens_vec
    }
}

impl AddAssign for Tokens {
    fn add_assign(&mut self, other: Self) {
        self.add_tokens(&other);
    }
}

impl AddAssign<&[Vec<u8>]> for Tokens {
    fn add_assign(&mut self, other: &[Vec<u8>]) {
        self.add_tokens(other);
    }
}

impl Add<&[Vec<u8>]> for Tokens {
    type Output = Self;
    fn add(self, other: &[Vec<u8>]) -> Self {
        let mut ret = self;
        ret.add_tokens(other);
        ret
    }
}

impl Add for Tokens {
    type Output = Self;

    fn add(self, other: Self) -> Self {
        self.add(other.tokens_vec.as_slice())
    }
}

impl<IT, V> From<IT> for Tokens
where
    IT: IntoIterator<Item = V>,
    V: AsRef<Vec<u8>>,
{
    fn from(tokens: IT) -> Self {
        let mut ret = Self::default();
        ret.add_tokens(tokens);
        ret
    }
}

impl AsSlice for Tokens {
    type Entry = Vec<u8>;
    fn as_slice(&self) -> &[Vec<u8>] {
        self.tokens()
    }
}

impl Add for &Tokens {
    type Output = Tokens;

    fn add(self, other: Self) -> Tokens {
        let mut ret: Tokens = self.clone();
        ret.add_tokens(other);
        ret
    }
}

impl<'it> IntoIterator for &'it Tokens {
    type Item = <Iter<'it, Vec<u8>> as Iterator>::Item;
    type IntoIter = Iter<'it, Vec<u8>>;

    fn into_iter(self) -> Self::IntoIter {
        self.as_slice().iter()
    }
}

/// Inserts a random token at a random position in the `Input`.
#[derive(Debug, Default)]
pub struct TokenInsert;

impl<I, S> Mutator<I, S> for TokenInsert
where
    S: HasMetadata + HasRand + HasMaxSize,
    I: HasBytesVec,
{
    fn mutate(
        &mut self,
        state: &mut S,
        input: &mut I,
        _stage_idx: i32,
    ) -> Result<MutationResult, Error> {
        let max_size = state.max_size();
        let tokens_len = {
            let meta = state.metadata().get::<Tokens>();
            if meta.is_none() {
                return Ok(MutationResult::Skipped);
            }
            if meta.unwrap().tokens().is_empty() {
                return Ok(MutationResult::Skipped);
            }
            meta.unwrap().tokens().len()
        };
        let token_idx = state.rand_mut().below(tokens_len as u64) as usize;

        let size = input.bytes().len();
        let off = state.rand_mut().below((size + 1) as u64) as usize;

        let meta = state.metadata().get::<Tokens>().unwrap();
        let token = &meta.tokens()[token_idx];
        let mut len = token.len();

        if size + len > max_size {
            if max_size > size {
                len = max_size - size;
            } else {
                return Ok(MutationResult::Skipped);
            }
        }

        input.bytes_mut().resize(size + len, 0);
        buffer_self_copy(input.bytes_mut(), off, off + len, size - off);
        buffer_copy(input.bytes_mut(), token, 0, off, len);

        Ok(MutationResult::Mutated)
    }
}

impl Named for TokenInsert {
    fn name(&self) -> &str {
        "TokenInsert"
    }
}

impl TokenInsert {
    /// Create a `TokenInsert` `Mutation`.
    #[must_use]
    pub fn new() -> Self {
        Self
    }
}

/// A `TokenReplace` [`Mutator`] replaces a random part of the input with one of a range of tokens.
/// From AFL terms, this is called as `Dictionary` mutation (which doesn't really make sense ;) ).
#[derive(Debug, Default)]
pub struct TokenReplace;

impl<I, S> Mutator<I, S> for TokenReplace
where
    S: UsesInput + HasMetadata + HasRand + HasMaxSize,
    I: HasBytesVec,
{
    fn mutate(
        &mut self,
        state: &mut S,
        input: &mut I,
        _stage_idx: i32,
    ) -> Result<MutationResult, Error> {
        let size = input.bytes().len();
        if size == 0 {
            return Ok(MutationResult::Skipped);
        }

        let tokens_len = {
            let meta = state.metadata().get::<Tokens>();
            if meta.is_none() {
                return Ok(MutationResult::Skipped);
            }
            if meta.unwrap().tokens().is_empty() {
                return Ok(MutationResult::Skipped);
            }
            meta.unwrap().tokens().len()
        };
        let token_idx = state.rand_mut().below(tokens_len as u64) as usize;

        let off = state.rand_mut().below(size as u64) as usize;

        let meta = state.metadata().get::<Tokens>().unwrap();
        let token = &meta.tokens()[token_idx];
        let mut len = token.len();
        if off + len > size {
            len = size - off;
        }

        buffer_copy(input.bytes_mut(), token, 0, off, len);

        Ok(MutationResult::Mutated)
    }
}

impl Named for TokenReplace {
    fn name(&self) -> &str {
        "TokenReplace"
    }
}

impl TokenReplace {
    /// Creates a new `TokenReplace` struct.
    #[must_use]
    pub fn new() -> Self {
        Self
    }
}

/// A `I2SRandReplace` [`Mutator`] replaces a random matching input-2-state comparison operand with the other.
/// It needs a valid [`CmpValuesMetadata`] in the state.
#[derive(Debug, Default)]
pub struct I2SRandReplace;

impl<I, S> Mutator<I, S> for I2SRandReplace
where
    S: UsesInput + HasMetadata + HasRand + HasMaxSize,
    I: HasBytesVec,
{
    #[allow(clippy::too_many_lines)]
    fn mutate(
        &mut self,
        state: &mut S,
        input: &mut I,
        _stage_idx: i32,
    ) -> Result<MutationResult, Error> {
        let size = input.bytes().len();
        if size == 0 {
            return Ok(MutationResult::Skipped);
        }

        let cmps_len = {
            let meta = state.metadata().get::<CmpValuesMetadata>();
            if meta.is_none() {
                return Ok(MutationResult::Skipped);
            }
            if meta.unwrap().list.is_empty() {
                return Ok(MutationResult::Skipped);
            }
            meta.unwrap().list.len()
        };
        let idx = state.rand_mut().below(cmps_len as u64) as usize;

        let off = state.rand_mut().below(size as u64) as usize;
        let len = input.bytes().len();
        let bytes = input.bytes_mut();

        let meta = state.metadata().get::<CmpValuesMetadata>().unwrap();
        let cmp_values = &meta.list[idx];

        let mut result = MutationResult::Skipped;
        match cmp_values {
            CmpValues::U8(v) => {
                for byte in bytes.iter_mut().take(len).skip(off) {
                    if *byte == v.0 {
                        *byte = v.1;
                        result = MutationResult::Mutated;
                        break;
                    } else if *byte == v.1 {
                        *byte = v.0;
                        result = MutationResult::Mutated;
                        break;
                    }
                }
            }
            CmpValues::U16(v) => {
                if len >= size_of::<u16>() {
                    for i in off..len - (size_of::<u16>() - 1) {
                        let val =
                            u16::from_ne_bytes(bytes[i..i + size_of::<u16>()].try_into().unwrap());
                        if val == v.0 {
                            let new_bytes = v.1.to_ne_bytes();
                            bytes[i..i + size_of::<u16>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val.swap_bytes() == v.0 {
                            let new_bytes = v.1.swap_bytes().to_ne_bytes();
                            bytes[i..i + size_of::<u16>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val == v.1 {
                            let new_bytes = v.0.to_ne_bytes();
                            bytes[i..i + size_of::<u16>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val.swap_bytes() == v.1 {
                            let new_bytes = v.0.swap_bytes().to_ne_bytes();
                            bytes[i..i + size_of::<u16>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        }
                    }
                }
            }
            CmpValues::U32(v) => {
                if len >= size_of::<u32>() {
                    for i in off..len - (size_of::<u32>() - 1) {
                        let val =
                            u32::from_ne_bytes(bytes[i..i + size_of::<u32>()].try_into().unwrap());
                        if val == v.0 {
                            let new_bytes = v.1.to_ne_bytes();
                            bytes[i..i + size_of::<u32>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val.swap_bytes() == v.0 {
                            let new_bytes = v.1.swap_bytes().to_ne_bytes();
                            bytes[i..i + size_of::<u32>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val == v.1 {
                            let new_bytes = v.0.to_ne_bytes();
                            bytes[i..i + size_of::<u32>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val.swap_bytes() == v.1 {
                            let new_bytes = v.0.swap_bytes().to_ne_bytes();
                            bytes[i..i + size_of::<u32>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        }
                    }
                }
            }
            CmpValues::U64(v) => {
                if len >= size_of::<u64>() {
                    for i in off..len - (size_of::<u64>() - 1) {
                        let val =
                            u64::from_ne_bytes(bytes[i..i + size_of::<u64>()].try_into().unwrap());
                        if val == v.0 {
                            let new_bytes = v.1.to_ne_bytes();
                            bytes[i..i + size_of::<u64>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val.swap_bytes() == v.0 {
                            let new_bytes = v.1.swap_bytes().to_ne_bytes();
                            bytes[i..i + size_of::<u64>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val == v.1 {
                            let new_bytes = v.0.to_ne_bytes();
                            bytes[i..i + size_of::<u64>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        } else if val.swap_bytes() == v.1 {
                            let new_bytes = v.0.swap_bytes().to_ne_bytes();
                            bytes[i..i + size_of::<u64>()].copy_from_slice(&new_bytes);
                            result = MutationResult::Mutated;
                            break;
                        }
                    }
                }
            }
            CmpValues::Bytes(v) => {
                'outer: for i in off..len {
                    let mut size = core::cmp::min(v.0.len(), len - i);
                    while size != 0 {
                        if v.0[0..size] == input.bytes()[i..i + size] {
                            buffer_copy(input.bytes_mut(), &v.1, 0, i, size);
                            result = MutationResult::Mutated;
                            break 'outer;
                        }
                        size -= 1;
                    }
                    size = core::cmp::min(v.1.len(), len - i);
                    while size != 0 {
                        if v.1[0..size] == input.bytes()[i..i + size] {
                            buffer_copy(input.bytes_mut(), &v.0, 0, i, size);
                            result = MutationResult::Mutated;
                            break 'outer;
                        }
                        size -= 1;
                    }
                }
            }
        }

        Ok(result)
    }
}

impl Named for I2SRandReplace {
    fn name(&self) -> &str {
        "I2SRandReplace"
    }
}

impl I2SRandReplace {
    /// Creates a new `I2SRandReplace` struct.
    #[must_use]
    pub fn new() -> Self {
        Self
    }
}

#[cfg(test)]
mod tests {
    #[cfg(feature = "std")]
    use std::fs;

    #[cfg(feature = "std")]
    use super::Tokens;

    #[cfg(feature = "std")]
    #[test]
    fn test_read_tokens() {
        let _res = fs::remove_file("test.tkns");
        let data = r###"
# comment
token1@123="AAA"
token1="A\x41A"
"A\AA"
token2="B"
        "###;
        fs::write("test.tkns", data).expect("Unable to write test.tkns");
        let tokens = Tokens::from_file("test.tkns").unwrap();
        #[cfg(feature = "std")]
        println!("Token file entries: {:?}", tokens.tokens());
        assert_eq!(tokens.tokens().len(), 2);
        let _res = fs::remove_file("test.tkns");
    }
}