use crate::error::*;
use std::fs;
use std::path::{Path, PathBuf};
use yaml_rust::yaml::{Yaml, YamlLoader};

#[derive(Clone, Debug)]
pub struct Config {
    pub delimiter: char,
    pub escape: bool,
    pub rm_whitespace: bool,
    pub template_dirs: Vec<PathBuf>,
    #[doc(hidden)]
    pub cache_dir: PathBuf,
    #[doc(hidden)]
    pub _non_exhaustive: (),
}

impl Default for Config {
    fn default() -> Self {
        Self {
            template_dirs: Vec::new(),
            delimiter: '%',
            escape: true,
            cache_dir: Path::new(env!("OUT_DIR")).join("cache"),
            rm_whitespace: false,
            _non_exhaustive: (),
        }
    }
}

impl Config {
    pub fn search_file_and_read(base: &Path) -> Result<Config, Error> {
        // search config file
        let mut path = PathBuf::new();
        let mut config = Config::default();

        for component in base.iter() {
            path.push(component);
            path.push("sailfish.yml");

            if path.is_file() {
                let config_file =
                    ConfigFile::read_from_file(&*path).map_err(|mut e| {
                        e.source_file = Some(path.to_owned());
                        e
                    })?;

                if let Some(template_dirs) = config_file.template_dirs {
                    for template_dir in template_dirs.into_iter().rev() {
                        if template_dir.is_absolute() {
                            config.template_dirs.push(template_dir);
                        } else {
                            config
                                .template_dirs
                                .push(path.parent().unwrap().join(template_dir));
                        }
                    }
                }

                if let Some(delimiter) = config_file.delimiter {
                    config.delimiter = delimiter;
                }

                if let Some(escape) = config_file.escape {
                    config.escape = escape;
                }

                if let Some(rm_whitespace) = config_file.rm_whitespace {
                    config.rm_whitespace = rm_whitespace;
                }
            }

            path.pop();
        }

        Ok(config)
    }
}

#[derive(Default)]
struct ConfigFile {
    template_dirs: Option<Vec<PathBuf>>,
    delimiter: Option<char>,
    escape: Option<bool>,
    rm_whitespace: Option<bool>,
}

impl ConfigFile {
    fn read_from_file(path: &Path) -> Result<Self, Error> {
        let mut config = Self::default();
        let content = fs::read_to_string(path)
            .chain_err(|| format!("Failed to read configuration file {:?}", path))?;

        let entries = YamlLoader::load_from_str(&*content)
            .map_err(|e| ErrorKind::ConfigError(e.to_string()))?;
        drop(content);

        for entry in entries {
            config.visit_global(entry)?
        }

        Ok(config)
    }

    fn visit_global(&mut self, entry: Yaml) -> Result<(), Error> {
        let hash = entry.into_hash().ok_or_else(|| {
            ErrorKind::ConfigError("Invalid configuration format".to_owned())
        })?;

        for (k, v) in hash {
            match k {
                Yaml::String(ref s) => match &**s {
                    "template_dir" => self.visit_template_dir(v)?,
                    "delimiter" => self.visit_delimiter(v)?,
                    "escape" => self.visit_escape(v)?,
                    "optimization" => self.visit_optimization(v)?,
                    _ => return Err(Self::error(format!("Unknown key ({})", s))),
                },
                _ => {
                    return Err(Self::error("Invalid configuration format"));
                }
            }
        }

        Ok(())
    }

    fn visit_template_dir(&mut self, value: Yaml) -> Result<(), Error> {
        if self.template_dirs.is_some() {
            return Err(Self::error("Duplicate key (template_dir)"));
        }

        match value {
            Yaml::String(s) => self.template_dirs = Some(vec![PathBuf::from(s)]),
            Yaml::Array(v) => {
                let mut template_dirs = Vec::new();
                for e in v {
                    if let Yaml::String(s) = e {
                        template_dirs.push(PathBuf::from(s));
                    } else {
                        return Err(Self::error(
                            "Arguments of `template_dir` must be string",
                        ));
                    }
                }
                self.template_dirs = Some(template_dirs);
            }
            _ => {
                return Err(Self::error("Arguments of `template_dir` must be string"));
            }
        }

        Ok(())
    }

    fn visit_delimiter(&mut self, value: Yaml) -> Result<(), Error> {
        if self.delimiter.is_some() {
            return Err(Self::error("Duplicate key (delimiter)"));
        }

        if let Yaml::String(s) = value {
            if s.chars().count() == 1 {
                self.delimiter = Some(s.chars().next().unwrap());
                Ok(())
            } else {
                Err(Self::error("`escape` must be single character"))
            }
        } else {
            Err(Self::error("`escape` must be single character"))
        }
    }

    fn visit_escape(&mut self, value: Yaml) -> Result<(), Error> {
        if self.escape.is_some() {
            return Err(Self::error("Duplicate key (escape)"));
        }

        if let Yaml::Boolean(b) = value {
            self.escape = Some(b);
            Ok(())
        } else {
            Err(Self::error("`escape` must be boolean"))
        }
    }

    fn visit_optimization(&mut self, entry: Yaml) -> Result<(), Error> {
        let hash = entry.into_hash().ok_or_else(|| {
            ErrorKind::ConfigError("Invalid configuration format".to_owned())
        })?;

        for (k, v) in hash {
            match k {
                Yaml::String(ref s) => match &**s {
                    "rm_whitespace" => self.visit_rm_whitespace(v)?,
                    _ => {
                        return Err(Self::error(format!(
                            "Unknown key (optimization.{})",
                            s
                        )));
                    }
                },
                _ => {
                    return Err(Self::error("Invalid configuration format"));
                }
            }
        }

        Ok(())
    }

    fn visit_rm_whitespace(&mut self, value: Yaml) -> Result<(), Error> {
        if self.rm_whitespace.is_some() {
            return Err(Self::error("Duplicate key (rm_whitespace)"));
        }

        if let Yaml::Boolean(b) = value {
            self.rm_whitespace = Some(b);
            Ok(())
        } else {
            Err(Self::error("`rm_whitespace` must be boolean"))
        }
    }

    fn error<T: Into<String>>(msg: T) -> Error {
        make_error!(ErrorKind::ConfigError(msg.into()))
    }
}