use libc::{c_int, c_void};
use std::marker::PhantomData;
use std::path::Path;
use std::ptr;

use crate::diff::{print_cb, LineCb};
use crate::util::{into_opt_c_string, Binding};
use crate::{raw, Blob, Buf, Diff, DiffDelta, DiffHunk, DiffLine, DiffOptions, Error};

/// A structure representing the text changes in a single diff delta.
///
/// This is an opaque structure.
pub struct Patch<'buffers> {
    raw: *mut raw::git_patch,
    buffers: PhantomData<&'buffers ()>,
}

unsafe impl<'buffers> Send for Patch<'buffers> {}

impl<'buffers> Binding for Patch<'buffers> {
    type Raw = *mut raw::git_patch;
    unsafe fn from_raw(raw: Self::Raw) -> Self {
        Patch {
            raw,
            buffers: PhantomData,
        }
    }
    fn raw(&self) -> Self::Raw {
        self.raw
    }
}

impl<'buffers> Drop for Patch<'buffers> {
    fn drop(&mut self) {
        unsafe { raw::git_patch_free(self.raw) }
    }
}

impl<'buffers> Patch<'buffers> {
    /// Return a Patch for one file in a Diff.
    ///
    /// Returns Ok(None) for an unchanged or binary file.
    pub fn from_diff(diff: &Diff<'buffers>, idx: usize) -> Result<Option<Self>, Error> {
        let mut ret = ptr::null_mut();
        unsafe {
            try_call!(raw::git_patch_from_diff(&mut ret, diff.raw(), idx));
            Ok(Binding::from_raw_opt(ret))
        }
    }

    /// Generate a Patch by diffing two blobs.
    pub fn from_blobs(
        old_blob: &Blob<'buffers>,
        old_path: Option<&Path>,
        new_blob: &Blob<'buffers>,
        new_path: Option<&Path>,
        opts: Option<&mut DiffOptions>,
    ) -> Result<Self, Error> {
        let mut ret = ptr::null_mut();
        let old_path = into_opt_c_string(old_path)?;
        let new_path = into_opt_c_string(new_path)?;
        unsafe {
            try_call!(raw::git_patch_from_blobs(
                &mut ret,
                old_blob.raw(),
                old_path,
                new_blob.raw(),
                new_path,
                opts.map(|s| s.raw())
            ));
            Ok(Binding::from_raw(ret))
        }
    }

    /// Generate a Patch by diffing a blob and a buffer.
    pub fn from_blob_and_buffer(
        old_blob: &Blob<'buffers>,
        old_path: Option<&Path>,
        new_buffer: &'buffers [u8],
        new_path: Option<&Path>,
        opts: Option<&mut DiffOptions>,
    ) -> Result<Self, Error> {
        let mut ret = ptr::null_mut();
        let old_path = into_opt_c_string(old_path)?;
        let new_path = into_opt_c_string(new_path)?;
        unsafe {
            try_call!(raw::git_patch_from_blob_and_buffer(
                &mut ret,
                old_blob.raw(),
                old_path,
                new_buffer.as_ptr() as *const c_void,
                new_buffer.len(),
                new_path,
                opts.map(|s| s.raw())
            ));
            Ok(Binding::from_raw(ret))
        }
    }

    /// Generate a Patch by diffing two buffers.
    pub fn from_buffers(
        old_buffer: &'buffers [u8],
        old_path: Option<&Path>,
        new_buffer: &'buffers [u8],
        new_path: Option<&Path>,
        opts: Option<&mut DiffOptions>,
    ) -> Result<Self, Error> {
        crate::init();
        let mut ret = ptr::null_mut();
        let old_path = into_opt_c_string(old_path)?;
        let new_path = into_opt_c_string(new_path)?;
        unsafe {
            try_call!(raw::git_patch_from_buffers(
                &mut ret,
                old_buffer.as_ptr() as *const c_void,
                old_buffer.len(),
                old_path,
                new_buffer.as_ptr() as *const c_void,
                new_buffer.len(),
                new_path,
                opts.map(|s| s.raw())
            ));
            Ok(Binding::from_raw(ret))
        }
    }

    /// Get the DiffDelta associated with the Patch.
    pub fn delta<'a>(&'a self) -> DiffDelta<'a> {
        unsafe { Binding::from_raw(raw::git_patch_get_delta(self.raw) as *mut _) }
    }

    /// Get the number of hunks in the Patch.
    pub fn num_hunks(&self) -> usize {
        unsafe { raw::git_patch_num_hunks(self.raw) }
    }

    /// Get the number of lines of context, additions, and deletions in the Patch.
    pub fn line_stats(&self) -> Result<(usize, usize, usize), Error> {
        let mut context = 0;
        let mut additions = 0;
        let mut deletions = 0;
        unsafe {
            try_call!(raw::git_patch_line_stats(
                &mut context,
                &mut additions,
                &mut deletions,
                self.raw
            ));
        }
        Ok((context, additions, deletions))
    }

    /// Get a DiffHunk and its total line count from the Patch.
    pub fn hunk<'a>(&'a self, hunk_idx: usize) -> Result<(DiffHunk<'a>, usize), Error> {
        let mut ret = ptr::null();
        let mut lines = 0;
        unsafe {
            try_call!(raw::git_patch_get_hunk(
                &mut ret, &mut lines, self.raw, hunk_idx
            ));
            Ok((Binding::from_raw(ret), lines))
        }
    }

    /// Get the number of lines in a hunk.
    pub fn num_lines_in_hunk(&self, hunk_idx: usize) -> Result<usize, Error> {
        unsafe { Ok(try_call!(raw::git_patch_num_lines_in_hunk(self.raw, hunk_idx)) as usize) }
    }

    /// Get a DiffLine from a hunk of the Patch.
    pub fn line_in_hunk<'a>(
        &'a self,
        hunk_idx: usize,
        line_of_hunk: usize,
    ) -> Result<DiffLine<'a>, Error> {
        let mut ret = ptr::null();
        unsafe {
            try_call!(raw::git_patch_get_line_in_hunk(
                &mut ret,
                self.raw,
                hunk_idx,
                line_of_hunk
            ));
            Ok(Binding::from_raw(ret))
        }
    }

    /// Get the size of a Patch's diff data in bytes.
    pub fn size(
        &self,
        include_context: bool,
        include_hunk_headers: bool,
        include_file_headers: bool,
    ) -> usize {
        unsafe {
            raw::git_patch_size(
                self.raw,
                include_context as c_int,
                include_hunk_headers as c_int,
                include_file_headers as c_int,
            )
        }
    }

    /// Print the Patch to text via a callback.
    pub fn print(&mut self, mut line_cb: &mut LineCb<'_>) -> Result<(), Error> {
        let ptr = &mut line_cb as *mut _ as *mut c_void;
        unsafe {
            let cb: raw::git_diff_line_cb = Some(print_cb);
            try_call!(raw::git_patch_print(self.raw, cb, ptr));
            Ok(())
        }
    }

    /// Get the Patch text as a Buf.
    pub fn to_buf(&mut self) -> Result<Buf, Error> {
        let buf = Buf::new();
        unsafe {
            try_call!(raw::git_patch_to_buf(buf.raw(), self.raw));
        }
        Ok(buf)
    }
}

impl<'buffers> std::fmt::Debug for Patch<'buffers> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
        let mut ds = f.debug_struct("Patch");
        ds.field("delta", &self.delta())
            .field("num_hunks", &self.num_hunks());
        if let Ok(line_stats) = &self.line_stats() {
            ds.field("line_stats", line_stats);
        }
        ds.finish()
    }
}
