use std::borrow::Cow;
use std::path::Path;

use serde::Deserialize;
use serde::Serialize;
use sha2::Digest;
use sha2::Sha256;

use crate::error::CustomError;

use super::Config;

#[derive(Debug, Deserialize, Serialize, Default)]
pub(crate) struct TargetConfig {
    pub(super) name: String,

    pub(super) repo: String,

    #[serde(default)]
    pub(super) branch: Option<String>,

    #[serde(default)]
    pub(super) revision: Option<String>,

    #[serde(default)]
    pub(super) path: Option<String>,

    #[serde(default)]
    pub(super) attr: String,

    #[serde(default)]
    pub(super) update: Option<bool>,

    #[serde(default)]
    pub(super) update_branch: Option<String>,
}

impl TargetConfig {
    /// The folder that contains the folders for the build targets.
    pub(crate) fn get_target_root_directory<'target, 'root>(
        &'target self,
        config_root: &'root Config,
    ) -> Result<Cow<'target, Path>, CustomError> {
        let output_directory = config_root.get_output_directory()?;
        Ok(Cow::Owned(output_directory.join("target")))
    }

    /// The root directory for this specific build target.
    pub(crate) fn get_target_directory<'target, 'root>(
        &'target self,
        config_root: &'root Config,
    ) -> Result<Cow<'target, Path>, CustomError> {
        let target_root = self.get_target_root_directory(config_root)?;
        Ok(Cow::Owned(target_root.join(&self.name)))
    }

    /// The folder that contains the folders containing the checkouts of the git repositories.
    pub(crate) fn get_repo_root_directory<'target, 'root>(
        &'target self,
        config_root: &'root Config,
    ) -> Result<Cow<'target, Path>, CustomError> {
        let output_directory = config_root.get_output_directory()?;
        Ok(Cow::Owned(output_directory.join("repo")))
    }

    /// The root of the checkout of the git repository.
    pub(crate) fn get_repo_directory<'target, 'root>(
        &'target self,
        config_root: &'root Config,
    ) -> Result<Cow<'target, Path>, CustomError> {
        let hashed_repo = Sha256::digest(&self.repo);
        let hashed_repo = hex_string(&hashed_repo);

        let repo_root = self.get_repo_root_directory(config_root)?;
        Ok(Cow::Owned(repo_root.join(hashed_repo)))
    }

    /// The directory that contains flake.nix.
    pub(crate) fn get_flake_directory<'target, 'root>(
        &'target self,
        config_root: &'root Config,
    ) -> Result<Cow<'target, Path>, CustomError> {
        let repo_directory = self.get_repo_directory(config_root)?;
        let subpath = self.path.as_deref();
        if let Some(subpath) = subpath {
            Ok(Cow::Owned(repo_directory.join(subpath)))
        } else {
            Ok(repo_directory)
        }
    }

    /// The URL to the upstream git repository.
    pub(crate) fn get_repo(&'_ self) -> Result<&String, CustomError> {
        Ok(&self.repo)
    }

    /// The git branch name to track.
    pub(crate) fn get_branch(&'_ self) -> Result<Cow<'_, str>, CustomError> {
        if let Some(b) = &self.branch {
            Ok(Cow::Borrowed(b))
        } else {
            Ok(Cow::Borrowed("main"))
        }
    }

    /// If we want to pin to a specific revision, this is the reference to that commit.
    pub(crate) fn get_revision(&self) -> Result<&Option<String>, CustomError> {
        Ok(&self.revision)
    }

    /// The folder where nixos-rebuild is invoked and the outputs are linked.
    pub(crate) fn get_build_directory<'target, 'root>(
        &'target self,
        config_root: &'root Config,
    ) -> Result<Cow<'target, Path>, CustomError> {
        let target_directory = self.get_target_directory(config_root)?;
        Ok(Cow::Owned(target_directory.join("build")))
    }

    /// The flake output attribute to build (the part after '#' in the build command).
    pub(crate) fn get_attr(&'_ self) -> Result<&String, CustomError> {
        Ok(&self.attr)
    }
}

fn hex_string(data: &[u8]) -> String {
    let mut out = String::with_capacity(data.len() * 2);
    for byte in data {
        out.push_str(format!("{:02x}", byte).as_str());
    }
    out
}