use git2::build::TreeUpdateBuilder;
use git2::FileMode;
use hyper::header;
use hyper::http::request::Parts;
use hyper::http::response::Builder;
use hyper::Body;
use hyper::StatusCode;
use multer::Multipart;
use serde::Deserialize;
use sputnik::hyper_body::SputnikBody;
use std::path::Path;
use std::str::from_utf8;

use crate::diff::diff;
use crate::forms::edit_text_form;
use crate::forms::move_form;
use crate::forms::EditForm;
use crate::forms::MoveForm;
use crate::get_renderer;
use crate::ActionParam;
use crate::Context;
use crate::HttpOrigin;
use crate::RenderMode;
use crate::Response;
use crate::{controller::Controller, Error};

pub(crate) async fn build_response<C: Controller>(
    host: &HttpOrigin,
    params: &ActionParam,
    controller: &C,
    ctx: Context<'_>,
    body: Body,
    parts: &mut Parts,
) -> Result<Response, Error> {
    if parts
        .headers
        .get(header::ORIGIN)
        .filter(|h| h.as_bytes() == host.origin.as_bytes())
        .is_none()
    {
        // This check prevents cross-site request forgery (CSRF).
        return Err(Error::BadRequest(format!(
            "POST requests must be sent with the header Origin: {}",
            host.origin
        )));
    }
    match params.action.as_ref() {
        "edit" => update_blob(body, controller, ctx, parts).await,
        "upload" => upload_blob(body, controller, ctx, parts).await,
        "move" => move_entry(body, controller, ctx, parts).await,
        "remove" => remove_entry(body, controller, ctx, parts).await,
        "diff" => diff_blob(body, controller, ctx, parts).await,
        "preview" => preview_edit(body, controller, ctx, parts).await,
        _ => Err(Error::BadRequest("unknown POST action".into())),
    }
}

fn commit_file_update<C: Controller>(
    data: &[u8],
    msg: Option<String>,
    controller: &C,
    ctx: &Context,
    parts: &Parts,
) -> Result<(), Error> {
    let blob_id = ctx.repo.blob(data)?;

    let mut builder = TreeUpdateBuilder::new();

    builder.upsert(ctx.path.as_str(), blob_id, FileMode::Blob);

    let (parent_tree, parent_commits) = if let Ok(commit) = ctx.branch_head() {
        let parent_tree = commit.tree()?;
        if parent_tree.get_path(ctx.path.as_ref()).ok().map(|e| e.id()) == Some(blob_id) {
            // nothing changed, don't create an empty commit
            return Err(Error::Redirect(parts.uri.path().to_string()));
        }
        (parent_tree, vec![commit])
    } else {
        // the empty tree exists even in empty bare repositories
        // we could also hard-code its hash here but magic strings are uncool
        let empty_tree = ctx.repo.find_tree(ctx.repo.index()?.write_tree()?)?;
        (empty_tree, vec![])
    };

    let new_tree_id = builder.create_updated(&ctx.repo, &parent_tree)?;

    let signature = controller.signature(&ctx.repo, parts)?;
    ctx.commit(
        &signature,
        &msg.filter(|m| !m.trim().is_empty()).unwrap_or_else(|| {
            format!(
                "{} {}",
                if parent_tree.get_path(ctx.path.as_ref()).is_ok() {
                    "edit"
                } else {
                    "create"
                },
                ctx.path
            )
        }),
        &ctx.repo.find_tree(new_tree_id)?,
        &parent_commits.iter().collect::<Vec<_>>()[..],
    )?;

    Ok(())
}

async fn update_blob<C: Controller>(
    body: Body,
    controller: &C,
    ctx: Context<'_>,
    parts: &mut Parts,
) -> Result<Response, Error> {
    if !controller.may_write_path(&ctx, parts) {
        return Err(Error::Unauthorized(
            "you are not authorized to edit this file".into(),
        ));
    }
    let mut data: EditForm = body.into_form().await?;

    if let Ok(commit) = ctx.branch_head() {
        // edit conflict detection
        let latest_oid = commit
            .tree()
            .unwrap()
            .get_path(ctx.path.as_ref())
            .ok()
            .map(|e| e.id().to_string());

        if data.oid != latest_oid {
            data.oid = latest_oid;
            return Ok(edit_text_form(&data, Some(
                if data.oid.is_some() {
                    "this file has been edited in the meantime, if you save you will overwrite the changes made since"
                }  else {
                    "this file has been deleted in the meantime, if you save you will re-create it"
                }
                ), controller, &ctx, parts).into());
        }
    }

    // normalize newlines as per HTML spec
    let text = data.text.replace("\r\n", "\n");
    if let Err(error) = controller.before_write(&text, &ctx, parts) {
        return Ok(edit_text_form(&data, Some(&error), controller, &ctx, parts).into());
    }

    commit_file_update(text.as_bytes(), data.msg, controller, &ctx, parts)?;

    controller.after_write(&ctx, parts);

    return Ok(Builder::new()
        .status(StatusCode::FOUND)
        .header("location", parts.uri.path())
        .body("redirecting".into())
        .unwrap()
        .into());
}

async fn upload_blob<C: Controller>(
    body: Body,
    controller: &C,
    ctx: Context<'_>,
    parts: &mut Parts,
) -> Result<Response, Error> {
    if !controller.may_write_path(&ctx, parts) {
        return Err(Error::Unauthorized(
            "you are not authorized to edit this file".into(),
        ));
    }
    // Extract the `multipart/form-data` boundary from the headers.
    let boundary = parts
        .headers
        .get(header::CONTENT_TYPE)
        .and_then(|ct| ct.to_str().ok())
        .and_then(|ct| multer::parse_boundary(ct).ok())
        .ok_or_else(|| Error::BadRequest("expected multipart/form-data".into()))?;

    let mut multipart = Multipart::new(Box::new(body), boundary);
    while let Some(field) = multipart
        .next_field()
        .await
        .map_err(|_| Error::BadRequest("failed to parse multipart".into()))?
    {
        if field.name() == Some("file") {
            // TODO: make commit message customizable
            commit_file_update(&field.bytes().await.unwrap(), None, controller, &ctx, parts)?;

            controller.after_write(&ctx, parts);

            return Ok(Builder::new()
                .status(StatusCode::FOUND)
                .header("location", parts.uri.path())
                .body("redirecting".into())
                .unwrap()
                .into());
        }
    }
    Err(Error::BadRequest(
        "expected file upload named 'file'".into(),
    ))
}

async fn move_entry<C: Controller>(
    body: Body,
    controller: &C,
    ctx: Context<'_>,
    parts: &Parts,
) -> Result<Response, Error> {
    if !controller.may_move_path(&ctx, parts) {
        return Err(Error::Unauthorized(
            "you are not authorized to move this file".into(),
        ));
    }
    let mut data: MoveForm = body.into_form().await?;
    let filename = ctx.path.file_name().unwrap();

    if ctx.path == Path::new(&data.dest) {
        return move_form(
            filename,
            &data,
            Some("can not move entry to itself"),
            controller,
            &ctx,
            parts,
        );
    }

    let parent_commit = ctx.branch_head()?;
    let parent_tree = parent_commit.tree().unwrap();
    if parent_tree.get_path(Path::new(&data.dest)).is_ok() {
        return move_form(
            filename,
            &data,
            Some("destination already exists"),
            controller,
            &ctx,
            parts,
        );
    }

    let mut builder = TreeUpdateBuilder::new();
    let entr = parent_tree.get_path(ctx.path.as_ref())?;
    builder.remove(&ctx.path.as_str());
    builder.upsert(
        &data.dest,
        entr.id(),
        match entr.filemode() {
            0o000000 => FileMode::Unreadable,
            0o040000 => FileMode::Tree,
            0o100644 => FileMode::Blob,
            0o100755 => FileMode::BlobExecutable,
            0o120000 => FileMode::Link,
            _ => {
                panic!("unexpected mode")
            }
        },
    );

    let new_tree_id = builder.create_updated(&ctx.repo, &parent_commit.tree()?)?;

    ctx.commit(
        &controller.signature(&ctx.repo, parts)?,
        &data
            .msg
            .take()
            .filter(|m| !m.trim().is_empty())
            .unwrap_or_else(|| format!("move {} to {}", ctx.path, data.dest)),
        &ctx.repo.find_tree(new_tree_id)?,
        &[&parent_commit],
    )?;

    Ok(Builder::new()
        .status(StatusCode::FOUND)
        .header(
            "location",
            controller.build_url_path(&ctx.branch, &data.dest),
        )
        .body("redirecting".into())
        .unwrap()
        .into())
}

#[derive(Deserialize)]
struct RemoveForm {
    msg: Option<String>,
}

async fn remove_entry<C: Controller>(
    body: Body,
    controller: &C,
    ctx: Context<'_>,
    parts: &Parts,
) -> Result<Response, Error> {
    if !controller.may_move_path(&ctx, parts) {
        return Err(Error::Unauthorized(
            "you are not authorized to remove this file".into(),
        ));
    }
    let data: RemoveForm = body.into_form().await?;
    let mut builder = TreeUpdateBuilder::new();
    builder.remove(&ctx.path.as_str());
    let parent_commit = ctx.branch_head()?;
    let new_tree_id = builder.create_updated(&ctx.repo, &parent_commit.tree()?)?;

    ctx.commit(
        &controller.signature(&ctx.repo, parts)?,
        &data
            .msg
            .filter(|m| !m.trim().is_empty())
            .unwrap_or_else(|| format!("remove {}", ctx.path)),
        &ctx.repo.find_tree(new_tree_id)?,
        &[&parent_commit],
    )?;
    Ok(Builder::new()
        .status(StatusCode::FOUND)
        .header(
            "location",
            controller.build_url_path(&ctx.branch, ctx.path.parent().unwrap().as_str()),
        )
        .body("redirecting".into())
        .unwrap()
        .into())
}

async fn diff_blob<C: Controller>(
    body: Body,
    controller: &C,
    ctx: Context<'_>,
    parts: &Parts,
) -> Result<Response, Error> {
    if !controller.may_write_path(&ctx, parts) {
        return Err(Error::Unauthorized(
            "you are not authorized to edit this file".into(),
        ));
    }

    let form: EditForm = body.into_form().await?;
    let new_text = form.text.replace("\r\n", "\n");

    let entr = ctx
        .branch_head()?
        .tree()
        .unwrap()
        .get_path(ctx.path.as_ref())?;

    let blob = ctx.repo.find_blob(entr.id()).unwrap();
    let old_text = from_utf8(blob.content())?;

    let mut page = edit_text_form(&form, None, controller, &ctx, parts);
    page.body.push_str(&diff(old_text, &new_text));
    Ok(page.into())
}

async fn preview_edit<C: Controller>(
    body: Body,
    controller: &C,
    ctx: Context<'_>,
    parts: &Parts,
) -> Result<Response, Error> {
    let form: EditForm = body.into_form().await?;
    let new_text = form.text.replace("\r\n", "\n");
    let mut page = edit_text_form(&form, None, controller, &ctx, parts);
    get_renderer(&ctx.path).unwrap()(&new_text, &mut page, RenderMode::Preview);
    Ok(page.into())
}