// Copyright 2014 Johannes Köster.
// Licensed under the MIT license (http://opensource.org/licenses/MIT)
// This file may not be copied, modified, or distributed
// except according to those terms.
//! Module for working with VCF or BCF headers.
//!
//! # Examples
//! From the header of a VCF file we can
//!   - Output sample count of a VCF file
//!   - Output sample names of a VCF file
//!   - Output sample index given a sample name of a VCF file.
//! ```
//! use crate::rust_htslib::bcf::{Reader, Read};
//! use std::io::Read as IoRead;
//!
//! let path = &"test/test_string.vcf";
//! let mut bcf = Reader::from_path(path).expect("Error opening file.");
//! let header = bcf.header();
//! assert_eq!(header.sample_count(), 2);  // Sample count
//! let mut s = String::new();
//! for (i, mut x) in header.samples().into_iter().enumerate() {
//!     x.read_to_string(&mut s);  // Read sample name in to `s`
//!     println!("{}", s);  // output sample name
//! }
//! assert_eq!(header.sample_id(b"one").unwrap(), 0);  // Sample index wrapped in Option<usize>
//! assert_eq!(header.sample_id(b"two").unwrap(), 1);  // Sample index wrapped in Option<usize>
//! assert!(header.sample_id(b"non existent sample").is_none());  // Return none if not found
//!
//! assert_eq!(header.contig_count(), 1); // Number of contig in header.
//! // obtain the data type of an INFO field
//! let (tag_type, tag_length) = header.info_type(b"S1").unwrap();
//! let (fmt_type, fmt_length) = header.format_type(b"GT").unwrap();
//! ```

use std::ffi;
use std::slice;
use std::str;

use crate::htslib;

use linear_map::LinearMap;

use crate::errors::{Error, Result};

pub type SampleSubset = Vec<i32>;

custom_derive! {
    /// A newtype for IDs from BCF headers.
    #[derive(
        NewtypeFrom,
        NewtypeDeref,
        PartialEq,
        PartialOrd,
        Eq,
        Ord,
        Copy,
        Clone,
        Debug
    )]
    pub struct Id(pub u32);
}

/// A BCF header.
#[derive(Debug)]
pub struct Header {
    pub inner: *mut htslib::bcf_hdr_t,
    pub subset: Option<SampleSubset>,
}

impl Default for Header {
    fn default() -> Self {
        Self::new()
    }
}

impl Header {
    /// Create a new (empty) `Header`.
    pub fn new() -> Self {
        let c_str = ffi::CString::new(&b"w"[..]).unwrap();
        Header {
            inner: unsafe { htslib::bcf_hdr_init(c_str.as_ptr()) },
            subset: None,
        }
    }

    /// Create a new `Header` using the given `HeaderView` as the template.
    ///
    /// After construction, you can modify the header independently from the template `header`.
    ///
    /// # Arguments
    ///
    /// - `header` - The `HeaderView` to use as the template.
    pub fn from_template(header: &HeaderView) -> Self {
        Header {
            inner: unsafe { htslib::bcf_hdr_dup(header.inner) },
            subset: None,
        }
    }

    /// Create a new `Header` using the given `HeaderView` as as template, but subsetting to the
    /// given `samples`.
    ///
    /// # Arguments
    ///
    /// - `header` - The `HeaderView` to use for the template.
    /// - `samples` - A slice of byte-encoded (`[u8]`) sample names.
    pub fn from_template_subset(header: &HeaderView, samples: &[&[u8]]) -> Result<Self> {
        let mut imap = vec![0; samples.len()];
        let names: Vec<_> = samples
            .iter()
            .map(|&s| ffi::CString::new(s).unwrap())
            .collect();
        let name_pointers: Vec<_> = names.iter().map(|s| s.as_ptr() as *mut i8).collect();
        let inner = unsafe {
            htslib::bcf_hdr_subset(
                header.inner,
                samples.len() as i32,
                name_pointers.as_ptr() as *const *mut i8,
                imap.as_mut_ptr() as *mut i32,
            )
        };
        if inner.is_null() {
            Err(Error::BcfDuplicateSampleNames)
        } else {
            Ok(Header {
                inner,
                subset: Some(imap),
            })
        }
    }

    /// Add a `sample` to the header.
    ///
    /// # Arguments
    ///
    /// - `sample` - Name of the sample to add (to the end of the sample list).
    pub fn push_sample(&mut self, sample: &[u8]) -> &mut Self {
        let c_str = ffi::CString::new(sample).unwrap();
        unsafe { htslib::bcf_hdr_add_sample(self.inner, c_str.as_ptr()) };
        self
    }

    /// Add a record to the header.
    ///
    /// # Arguments
    ///
    /// - `record` - String representation of the header line
    ///
    /// # Example
    ///
    /// ```rust,ignore
    /// header.push_record(format!("##contig=<ID={},length={}>", "chrX", 155270560).as_bytes());
    /// ```
    pub fn push_record(&mut self, record: &[u8]) -> &mut Self {
        let c_str = ffi::CString::new(record).unwrap();
        unsafe { htslib::bcf_hdr_append(self.inner, c_str.as_ptr()) };
        self
    }

    /// Remove a `FILTER` entry from the header.
    ///
    /// # Arguments
    ///
    /// - `tag` - Name of the `FLT` tag to remove.
    pub fn remove_filter(&mut self, tag: &[u8]) -> &mut Self {
        self.remove_impl(tag, htslib::BCF_HL_FLT)
    }

    /// Remove an `INFO` entry from the header.
    ///
    /// # Arguments
    ///
    /// - `tag` - Name of the `INFO` tag to remove.
    pub fn remove_info(&mut self, tag: &[u8]) -> &mut Self {
        self.remove_impl(tag, htslib::BCF_HL_INFO)
    }

    /// Remove a `FORMAT` entry from the header.
    ///
    /// # Arguments
    ///
    /// - `tag` - Name of the `FORMAT` tag to remove.
    pub fn remove_format(&mut self, tag: &[u8]) -> &mut Self {
        self.remove_impl(tag, htslib::BCF_HL_FMT)
    }

    /// Remove a contig entry from the header.
    ///
    /// # Arguments
    ///
    /// - `tag` - Name of the `FORMAT` tag to remove.
    pub fn remove_contig(&mut self, tag: &[u8]) -> &mut Self {
        self.remove_impl(tag, htslib::BCF_HL_CTG)
    }

    /// Remove a structured entry from the header.
    ///
    /// # Arguments
    ///
    /// - `tag` - Name of the structured tag to remove.
    pub fn remove_structured(&mut self, tag: &[u8]) -> &mut Self {
        self.remove_impl(tag, htslib::BCF_HL_STR)
    }

    /// Remove a generic entry from the header.
    ///
    /// # Arguments
    ///
    /// - `tag` - Name of the generic tag to remove.
    pub fn remove_generic(&mut self, tag: &[u8]) -> &mut Self {
        self.remove_impl(tag, htslib::BCF_HL_GEN)
    }

    /// Implementation of removing header tags.
    fn remove_impl(&mut self, tag: &[u8], type_: u32) -> &mut Self {
        unsafe {
            let v = tag.to_vec();
            let c_str = ffi::CString::new(v).unwrap();
            htslib::bcf_hdr_remove(self.inner, type_ as i32, c_str.as_ptr());
        }
        self
    }
}

impl Drop for Header {
    fn drop(&mut self) {
        unsafe { htslib::bcf_hdr_destroy(self.inner) };
    }
}

/// A header record.
#[derive(Debug)]
pub enum HeaderRecord {
    /// A `FILTER` header record.
    Filter {
        key: String,
        values: LinearMap<String, String>,
    },
    /// An `INFO` header record.
    Info {
        key: String,
        values: LinearMap<String, String>,
    },
    /// A `FORMAT` header record.
    Format {
        key: String,
        values: LinearMap<String, String>,
    },
    /// A `contig` header record.
    Contig {
        key: String,
        values: LinearMap<String, String>,
    },
    /// A structured header record.
    Structured {
        key: String,
        values: LinearMap<String, String>,
    },
    /// A generic, unstructured header record.
    Generic { key: String, value: String },
}

#[derive(Debug)]
pub struct HeaderView {
    pub inner: *mut htslib::bcf_hdr_t,
}

impl HeaderView {
    pub fn new(inner: *mut htslib::bcf_hdr_t) -> Self {
        HeaderView { inner }
    }

    #[inline]
    fn inner(&self) -> htslib::bcf_hdr_t {
        unsafe { *self.inner }
    }

    /// Get the number of samples defined in the header.
    pub fn sample_count(&self) -> u32 {
        self.inner().n[htslib::BCF_DT_SAMPLE as usize] as u32
    }

    /// Get vector of sample names defined in the header.
    pub fn samples(&self) -> Vec<&[u8]> {
        let names =
            unsafe { slice::from_raw_parts(self.inner().samples, self.sample_count() as usize) };
        names
            .iter()
            .map(|name| unsafe { ffi::CStr::from_ptr(*name).to_bytes() })
            .collect()
    }

    /// Obtain id (column index) of given sample.
    /// Returns `None` if sample is not present in header.
    pub fn sample_id(&self, sample: &[u8]) -> Option<usize> {
        self.samples().iter().position(|s| *s == sample)
    }

    /// Get the number of contigs defined in the header.
    pub fn contig_count(&self) -> u32 {
        self.inner().n[htslib::BCF_DT_CTG as usize] as u32
    }

    pub fn rid2name(&self, rid: u32) -> Result<&[u8]> {
        if rid <= self.contig_count() {
            unsafe {
                let dict = self.inner().id[htslib::BCF_DT_CTG as usize];
                let ptr = (*dict.offset(rid as isize)).key;
                Ok(ffi::CStr::from_ptr(ptr).to_bytes())
            }
        } else {
            Err(Error::BcfUnknownRID { rid })
        }
    }

    /// Retrieve the (internal) chromosome identifier
    /// # Examples
    /// ```rust
    /// use rust_htslib::bcf::header::Header;
    /// use rust_htslib::bcf::{Format, Writer};
    ///
    /// let mut header = Header::new();
    /// let contig_field = br#"##contig=<ID=foo,length=10>"#;
    /// header.push_record(contig_field);
    /// let mut vcf = Writer::from_stdout(&header, true, Format::Vcf).unwrap();
    /// let header_view = vcf.header();
    /// let rid = header_view.name2rid(b"foo").unwrap();
    /// assert_eq!(rid, 0);
    /// // try and retrieve a contig not in the header
    /// let result = header_view.name2rid(b"bar");
    /// assert!(result.is_err())
    /// ```
    /// # Errors
    /// If `name` does not match a chromosome currently in the VCF header, returns [`Error::BcfUnknownContig`]
    pub fn name2rid(&self, name: &[u8]) -> Result<u32> {
        let c_str = ffi::CString::new(name).unwrap();
        unsafe {
            match htslib::bcf_hdr_id2int(
                self.inner,
                htslib::BCF_DT_CTG as i32,
                c_str.as_ptr() as *mut i8,
            ) {
                -1 => Err(Error::BcfUnknownContig {
                    contig: str::from_utf8(name).unwrap().to_owned(),
                }),
                i => Ok(i as u32),
            }
        }
    }

    pub fn info_type(&self, tag: &[u8]) -> Result<(TagType, TagLength)> {
        self.tag_type(tag, htslib::BCF_HL_INFO)
    }

    pub fn format_type(&self, tag: &[u8]) -> Result<(TagType, TagLength)> {
        self.tag_type(tag, htslib::BCF_HL_FMT)
    }

    fn tag_type(&self, tag: &[u8], hdr_type: ::libc::c_uint) -> Result<(TagType, TagLength)> {
        let tag_desc = || str::from_utf8(tag).unwrap().to_owned();
        let c_str_tag = ffi::CString::new(tag).unwrap();
        let (_type, length, num_values) = unsafe {
            let id = htslib::bcf_hdr_id2int(
                self.inner,
                htslib::BCF_DT_ID as i32,
                c_str_tag.as_ptr() as *mut i8,
            );
            if id < 0 {
                return Err(Error::BcfUndefinedTag { tag: tag_desc() });
            }
            let n = (*self.inner).n[htslib::BCF_DT_ID as usize] as usize;
            let entry = slice::from_raw_parts((*self.inner).id[htslib::BCF_DT_ID as usize], n);
            let d = (*entry[id as usize].val).info[hdr_type as usize];
            (d >> 4 & 0xf, d >> 8 & 0xf, d >> 12)
        };
        let _type = match _type as ::libc::c_uint {
            htslib::BCF_HT_FLAG => TagType::Flag,
            htslib::BCF_HT_INT => TagType::Integer,
            htslib::BCF_HT_REAL => TagType::Float,
            htslib::BCF_HT_STR => TagType::String,
            _ => return Err(Error::BcfUnexpectedType { tag: tag_desc() }),
        };
        let length = match length as ::libc::c_uint {
            // XXX: Hacky "as u32" cast. Trace back through unsafe{} towards BCF struct and rollback to proper type
            htslib::BCF_VL_FIXED => TagLength::Fixed(num_values as u32),
            htslib::BCF_VL_VAR => TagLength::Variable,
            htslib::BCF_VL_A => TagLength::AltAlleles,
            htslib::BCF_VL_R => TagLength::Alleles,
            htslib::BCF_VL_G => TagLength::Genotypes,
            _ => return Err(Error::BcfUnexpectedType { tag: tag_desc() }),
        };

        Ok((_type, length))
    }

    /// Convert string ID (e.g., for a `FILTER` value) to its numeric identifier.
    pub fn name_to_id(&self, id: &[u8]) -> Result<Id> {
        let c_str = ffi::CString::new(id).unwrap();
        unsafe {
            match htslib::bcf_hdr_id2int(
                self.inner,
                htslib::BCF_DT_ID as i32,
                c_str.as_ptr() as *const i8,
            ) {
                -1 => Err(Error::BcfUnknownID {
                    id: str::from_utf8(id).unwrap().to_owned(),
                }),
                i => Ok(Id(i as u32)),
            }
        }
    }

    /// Convert integer representing an identifier (e.g., a `FILTER` value) to its string
    /// name.bam.
    pub fn id_to_name(&self, id: Id) -> Vec<u8> {
        let key = unsafe {
            ffi::CStr::from_ptr(
                (*(*self.inner).id[htslib::BCF_DT_ID as usize].offset(*id as isize)).key,
            )
        };
        key.to_bytes().to_vec()
    }

    /// Convert string sample name to its numeric identifier.
    pub fn sample_to_id(&self, id: &[u8]) -> Result<Id> {
        let c_str = ffi::CString::new(id).unwrap();
        unsafe {
            match htslib::bcf_hdr_id2int(
                self.inner,
                htslib::BCF_DT_SAMPLE as i32,
                c_str.as_ptr() as *const i8,
            ) {
                -1 => Err(Error::BcfUnknownSample {
                    name: str::from_utf8(id).unwrap().to_owned(),
                }),
                i => Ok(Id(i as u32)),
            }
        }
    }

    /// Convert integer representing an contig to its name.
    pub fn id_to_sample(&self, id: Id) -> Vec<u8> {
        let key = unsafe {
            ffi::CStr::from_ptr(
                (*(*self.inner).id[htslib::BCF_DT_SAMPLE as usize].offset(*id as isize)).key,
            )
        };
        key.to_bytes().to_vec()
    }

    /// Return structured `HeaderRecord`s.
    pub fn header_records(&self) -> Vec<HeaderRecord> {
        fn parse_kv(rec: &htslib::bcf_hrec_t) -> LinearMap<String, String> {
            let mut result: LinearMap<String, String> = LinearMap::new();
            for i in 0_i32..(rec.nkeys) {
                let key = unsafe {
                    ffi::CStr::from_ptr(*rec.keys.offset(i as isize))
                        .to_str()
                        .unwrap()
                        .to_string()
                };
                let value = unsafe {
                    ffi::CStr::from_ptr(*rec.vals.offset(i as isize))
                        .to_str()
                        .unwrap()
                        .to_string()
                };
                result.insert(key, value);
            }
            result
        }

        let mut result: Vec<HeaderRecord> = Vec::new();
        for i in 0_i32..unsafe { (*self.inner).nhrec } {
            let rec = unsafe { &(**(*self.inner).hrec.offset(i as isize)) };
            let key = unsafe { ffi::CStr::from_ptr(rec.key).to_str().unwrap().to_string() };
            let record = match rec.type_ {
                0 => HeaderRecord::Filter {
                    key,
                    values: parse_kv(rec),
                },
                1 => HeaderRecord::Info {
                    key,
                    values: parse_kv(rec),
                },
                2 => HeaderRecord::Format {
                    key,
                    values: parse_kv(rec),
                },
                3 => HeaderRecord::Contig {
                    key,
                    values: parse_kv(rec),
                },
                4 => HeaderRecord::Structured {
                    key,
                    values: parse_kv(rec),
                },
                5 => HeaderRecord::Generic {
                    key,
                    value: unsafe { ffi::CStr::from_ptr(rec.value).to_str().unwrap().to_string() },
                },
                _ => panic!("Unknown type: {}", rec.type_),
            };
            result.push(record);
        }
        result
    }
}

impl Clone for HeaderView {
    fn clone(&self) -> Self {
        HeaderView {
            inner: unsafe { htslib::bcf_hdr_dup(self.inner) },
        }
    }
}

impl Drop for HeaderView {
    fn drop(&mut self) {
        unsafe {
            htslib::bcf_hdr_destroy(self.inner);
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum TagType {
    Flag,
    Integer,
    Float,
    String,
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum TagLength {
    Fixed(u32),
    AltAlleles,
    Alleles,
    Genotypes,
    Variable,
}