use serde::{Deserialize, Serialize};
use std::{
    collections::{hash_map::Entry, HashMap},
    fmt,
    path::{Path, PathBuf},
    str::FromStr,
};

const DAPPTOOLS_CONTRACTS_DIR: &str = "src";
const DAPPTOOLS_LIB_DIR: &str = "lib";
const JS_CONTRACTS_DIR: &str = "contracts";

/// The solidity compiler can only reference files that exist locally on your computer.
/// So importing directly from GitHub (as an example) is not possible.
///
/// Let's imagine you want to use OpenZeppelin's amazing library of smart contracts,
/// @openzeppelin/contracts-ethereum-package:
///
/// ```ignore
/// pragma solidity 0.5.11;
///
/// import "@openzeppelin/contracts-ethereum-package/contracts/math/SafeMath.sol";
///
/// contract MyContract {
///     using SafeMath for uint256;
///     ...
/// }
/// ```
///
/// When using solc, you have to specify the following:
///
/// "prefix" = the path that's used in your smart contract, i.e.
/// "@openzeppelin/contracts-ethereum-package" "target" = the absolute path of OpenZeppelin's
/// contracts downloaded on your computer
///
/// The format looks like this:
/// `solc prefix=target ./MyContract.sol`
///
/// solc --bin
/// @openzeppelin/contracts-ethereum-package=/Your/Absolute/Path/To/@openzeppelin/
/// contracts-ethereum-package ./MyContract.sol
///
/// [Source](https://ethereum.stackexchange.com/questions/74448/what-are-remappings-and-how-do-they-work-in-solidity)
#[derive(Clone, Debug, PartialEq, PartialOrd, Eq, Ord)]
pub struct Remapping {
    pub name: String,
    pub path: String,
}

#[derive(thiserror::Error, Debug, PartialEq, PartialOrd)]
pub enum RemappingError {
    #[error("no prefix found")]
    NoPrefix,
    #[error("no target found")]
    NoTarget,
}

impl FromStr for Remapping {
    type Err = RemappingError;

    fn from_str(remapping: &str) -> std::result::Result<Self, Self::Err> {
        let (name, path) = remapping.split_once('=').ok_or(RemappingError::NoPrefix)?;
        if name.trim().is_empty() {
            return Err(RemappingError::NoPrefix)
        }
        if path.trim().is_empty() {
            return Err(RemappingError::NoTarget)
        }
        Ok(Remapping { name: name.to_string(), path: path.to_string() })
    }
}

impl Serialize for Remapping {
    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
    where
        S: serde::ser::Serializer,
    {
        serializer.serialize_str(&self.to_string())
    }
}

impl<'de> Deserialize<'de> for Remapping {
    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
    where
        D: serde::de::Deserializer<'de>,
    {
        let remapping = String::deserialize(deserializer)?;
        Remapping::from_str(&remapping).map_err(serde::de::Error::custom)
    }
}

// Remappings are printed as `prefix=target`
impl fmt::Display for Remapping {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}={}", self.name, self.path)
    }
}

impl Remapping {
    /// Returns all formatted remappings
    pub fn find_many_str(path: &str) -> Vec<String> {
        Self::find_many(path).into_iter().map(|r| r.to_string()).collect()
    }

    /// Attempts to autodetect all remappings given a certain root path.
    ///
    /// This will recursively scan all subdirectories of the root path, if a subdirectory contains a
    /// solidity file then this a candidate for a remapping. The name of the remapping will be the
    /// folder name.
    ///
    /// However, there are additional rules/assumptions when it comes to determining if a candidate
    /// should in fact be a remapping:
    ///
    /// All names and paths end with a trailing "/"
    ///
    /// The name of the remapping will be the parent folder of a solidity file, unless the folder is
    /// named `src`, `lib` or `contracts` in which case the name of the remapping will be the parent
    /// folder's name of `src`, `lib`, `contracts`: The remapping of `repo1/src/contract.sol` is
    /// `name: "repo1/", path: "repo1/src/"`
    ///
    /// Nested remappings need to be separated by `src`, `lib` or `contracts`, The remapping of
    /// `repo1/lib/ds-math/src/contract.sol` is `name: "ds-match/", "repo1/lib/ds-math/src/"`
    ///
    /// Remapping detection is primarily designed for dapptool's rules for lib folders, however, we
    /// attempt to detect and optimize various folder structures commonly used in `node_modules`
    /// dependencies. For those the same rules apply. In addition, we try to unify all
    /// remappings discovered according to the rules mentioned above, so that layouts like,
    //   @aave/
    //   ├─ governance/
    //   │  ├─ contracts/
    //   ├─ protocol-v2/
    //   │  ├─ contracts/
    ///
    /// which would be multiple rededications according to our rules ("governance", "protocol-v2"),
    /// are unified into `@aave` by looking at their common ancestor, the root of this subdirectory
    /// (`@aave`)
    pub fn find_many(root: impl AsRef<Path>) -> Vec<Remapping> {
        /// prioritize ("a", "1/2") over ("a", "1/2/3")
        fn insert_higher_path(mappings: &mut HashMap<String, PathBuf>, key: String, path: PathBuf) {
            match mappings.entry(key) {
                Entry::Occupied(mut e) => {
                    if e.get().components().count() > path.components().count() {
                        e.insert(path);
                    }
                }
                Entry::Vacant(e) => {
                    e.insert(path);
                }
            }
        }

        let mut remappings = HashMap::new();
        // iterate over all dirs that are children of the root
        for dir in walkdir::WalkDir::new(root)
            .follow_links(true)
            .min_depth(1)
            .max_depth(1)
            .into_iter()
            .filter_map(std::result::Result::ok)
            .filter(|e| e.file_type().is_dir())
        {
            let dir_path = dir.path();

            // in node_modules there could be following pattern:
            //   @aave/
            //   ├─ governance/
            //   │  ├─ contracts/
            //   ├─ protocol-v2/
            //   │  ├─ contracts/
            // in such cases, the desired remapping name would be `@aave`, but at this point we
            // would have detected `governance` and `protocol-v2` as remapping names. so
            // now we need to unify them by checking if they share the `dir_path` as
            // common ancestor. We make the assumption here, that we can only unify
            // remappings if their direct parent dir is the root, so `@aave/lib` or
            // `@aave/src` is not mergeable as that would violate dapptools style lib paths and
            // remappings. This means we can only unify/simplify them if there is no! `src` or `lib`
            // path between the remappings' path and the dir_path
            if let Some(root_name) = dir_path.file_name().and_then(|f| f.to_str()) {
                let mut simplified = false;
                // check all remappings in this depth 1 folder
                'outer: for (name, path) in scan_children(dir_path) {
                    let mut p = path.as_path();
                    let mut first_parent = true;
                    while let Some(parent) = p.parent() {
                        if parent == dir_path {
                            if !simplified {
                                // handle trailing src,lib,contracts dir in cases like
                                // `dir_path/@ens/contracts`
                                let path = if first_parent { path } else { dir_path.to_path_buf() };
                                insert_higher_path(
                                    &mut remappings,
                                    format!("{}/", root_name),
                                    path,
                                );
                                simplified = true;
                            }
                            continue 'outer
                        }
                        if parent.ends_with(DAPPTOOLS_CONTRACTS_DIR) ||
                            parent.ends_with(DAPPTOOLS_LIB_DIR)
                        {
                            // end early
                            insert_higher_path(&mut remappings, name, path);
                            continue 'outer
                        }
                        first_parent = false;
                        p = parent;
                    }
                }
            }
        }
        remappings
            .into_iter()
            .map(|(name, path)| Remapping { name, path: format!("{}/", path.display()) })
            .collect()
    }
}

/// Recursively scans sub folders and checks if they contain a solidity file
fn scan_children(root: &Path) -> HashMap<String, PathBuf> {
    // this is a marker if the current root is already a remapping
    let mut remapping = false;

    // all found remappings
    let mut remappings = HashMap::new();

    for entry in walkdir::WalkDir::new(&root)
        .min_depth(1)
        .max_depth(1)
        .into_iter()
        .filter_map(std::result::Result::ok)
    {
        let entry: walkdir::DirEntry = entry;

        if entry.file_type().is_file() && !remapping {
            if entry.file_name().to_str().filter(|f| f.ends_with(".sol")).is_some() {
                // found a solidity file

                // this will hold the actual root remapping if root is named `src` or `lib`
                let actual_parent = root.parent().filter(|_| {
                    root.ends_with(DAPPTOOLS_CONTRACTS_DIR) ||
                        root.ends_with(DAPPTOOLS_LIB_DIR) ||
                        root.ends_with(JS_CONTRACTS_DIR)
                });

                let parent = actual_parent.unwrap_or(root);
                if let Some(name) = parent.file_name().and_then(|f| f.to_str()) {
                    remappings.insert(format!("{}/", name), root.to_path_buf());
                    remapping = true;
                }
            }
        } else if entry.file_type().is_dir() {
            let path = entry.path();
            // we skip `tests` and nested `node_modules`
            if !path.ends_with("tests") || !path.ends_with("node_modules") {
                for (name, path) in scan_children(path) {
                    if let Entry::Vacant(e) = remappings.entry(name) {
                        e.insert(path);
                    }
                }
            }
        }
    }

    remappings
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn serde() {
        let remapping = "oz=../b/c/d";
        let remapping = Remapping::from_str(remapping).unwrap();
        assert_eq!(remapping.name, "oz".to_string());
        assert_eq!(remapping.path, "../b/c/d".to_string());

        let err = Remapping::from_str("").unwrap_err();
        assert_eq!(err, RemappingError::NoPrefix);

        let err = Remapping::from_str("oz=").unwrap_err();
        assert_eq!(err, RemappingError::NoTarget);
    }

    // https://doc.rust-lang.org/rust-by-example/std_misc/fs.html
    fn touch(path: &std::path::Path) -> std::io::Result<()> {
        match std::fs::OpenOptions::new().create(true).write(true).open(path) {
            Ok(_) => Ok(()),
            Err(e) => Err(e),
        }
    }

    fn mkdir_or_touch(tmp: &std::path::Path, paths: &[&str]) {
        for path in paths {
            if path.ends_with(".sol") {
                let path = tmp.join(path);
                touch(&path).unwrap();
            } else {
                let path = tmp.join(path);
                std::fs::create_dir_all(&path).unwrap();
            }
        }
    }

    // helper function for converting path bufs to remapping strings
    fn to_str(p: std::path::PathBuf) -> String {
        format!("{}/", p.display())
    }

    #[test]
    fn find_remapping_dapptools() {
        let tmp_dir = tempdir::TempDir::new("lib").unwrap();
        let tmp_dir_path = tmp_dir.path();
        let paths = ["repo1/src/", "repo1/src/contract.sol"];
        mkdir_or_touch(tmp_dir_path, &paths[..]);

        let path = tmp_dir_path.join("repo1").display().to_string();
        let remappings = Remapping::find_many(tmp_dir_path);
        // repo1/=lib/repo1/src
        assert_eq!(remappings.len(), 1);

        assert_eq!(remappings[0].name, "repo1/");
        assert_eq!(remappings[0].path, format!("{}/src/", path));
    }

    #[test]
    fn recursive_remappings() {
        let tmp_dir = tempdir::TempDir::new("lib").unwrap();
        let tmp_dir_path = tmp_dir.path();
        let paths = [
            "repo1/src/",
            "repo1/src/contract.sol",
            "repo1/lib/",
            "repo1/lib/ds-math/src/",
            "repo1/lib/ds-math/src/contract.sol",
            "repo1/lib/ds-math/lib/ds-test/src/",
            "repo1/lib/ds-math/lib/ds-test/src/test.sol",
        ];
        mkdir_or_touch(tmp_dir_path, &paths[..]);

        let path = tmp_dir_path.display().to_string();
        let mut remappings = Remapping::find_many(&path);
        remappings.sort_unstable();

        let mut expected = vec![
            Remapping {
                name: "repo1/".to_string(),
                path: to_str(tmp_dir_path.join("repo1").join("src")),
            },
            Remapping {
                name: "ds-math/".to_string(),
                path: to_str(tmp_dir_path.join("repo1").join("lib").join("ds-math").join("src")),
            },
            Remapping {
                name: "ds-test/".to_string(),
                path: to_str(
                    tmp_dir_path
                        .join("repo1")
                        .join("lib")
                        .join("ds-math")
                        .join("lib")
                        .join("ds-test")
                        .join("src"),
                ),
            },
        ];
        expected.sort_unstable();
        assert_eq!(remappings, expected);
    }

    #[test]
    fn remappings() {
        let tmp_dir = tempdir::TempDir::new("lib").unwrap();
        let repo1 = tmp_dir.path().join("src_repo");
        let repo2 = tmp_dir.path().join("contracts_repo");

        let dir1 = repo1.join("src");
        std::fs::create_dir_all(&dir1).unwrap();

        let dir2 = repo2.join("contracts");
        std::fs::create_dir_all(&dir2).unwrap();

        let contract1 = dir1.join("contract.sol");
        touch(&contract1).unwrap();

        let contract2 = dir2.join("contract.sol");
        touch(&contract2).unwrap();

        let path = tmp_dir.path().display().to_string();
        let mut remappings = Remapping::find_many(&path);
        remappings.sort_unstable();
        let mut expected = vec![
            Remapping {
                name: "src_repo/".to_string(),
                path: format!("{}/", dir1.into_os_string().into_string().unwrap()),
            },
            Remapping {
                name: "contracts_repo/".to_string(),
                path: format!("{}/", dir2.into_os_string().into_string().unwrap()),
            },
        ];
        expected.sort_unstable();
        assert_eq!(remappings, expected);
    }

    #[test]
    fn hardhat_remappings() {
        let tmp_dir = tempdir::TempDir::new("node_modules").unwrap();
        let tmp_dir_node_modules = tmp_dir.path().join("node_modules");
        let paths = [
            "node_modules/@aave/aave-token/contracts/token/",
            "node_modules/@aave/aave-token/contracts/token/AaveToken.sol",
            "node_modules/@aave/governance-v2/contracts/governance/",
            "node_modules/@aave/governance-v2/contracts/governance/Executor.sol",
            "node_modules/@aave/protocol-v2/contracts/protocol/lendingpool/",
            "node_modules/@aave/protocol-v2/contracts/protocol/lendingpool/LendingPool.sol",
            "node_modules/@ensdomains/ens/contracts/",
            "node_modules/@ensdomains/ens/contracts/contract.sol",
        ];
        mkdir_or_touch(tmp_dir.path(), &paths[..]);
        let mut remappings = Remapping::find_many(&tmp_dir_node_modules);
        remappings.sort_unstable();
        let mut expected = vec![
            Remapping {
                name: "@aave/".to_string(),
                path: to_str(tmp_dir_node_modules.join("@aave")),
            },
            Remapping {
                name: "@ensdomains/".to_string(),
                path: to_str(tmp_dir_node_modules.join("@ensdomains")),
            },
        ];
        expected.sort_unstable();

        assert_eq!(remappings, expected);
    }
}