use anyhow::{Context, Result};
use serde::Deserialize;
use std::{fs::File, io::BufReader, path::Path};

/// Email server credentials.
#[derive(Deserialize)]
pub struct EmailCredentials {
    pub domain: String,
    pub username: String,
    pub password: String,
}

#[derive(Deserialize)]
pub struct Email {
    pub from: String,
    pub to: String,
    pub credentials: EmailCredentials,
}

/// UTC offset for time formatting.
#[derive(Deserialize, Default)]
#[serde(default)]
pub struct UtcOffset {
    pub hours: i8,
    pub minutes: i8,
}

#[derive(Deserialize)]
#[serde(tag = "type")]
pub enum CustomFieldType {
    Text,
    Textarea { rows: u8 },
}

#[derive(Deserialize)]
pub struct CustomField {
    pub key: String,
    pub label: String,
    #[serde(default)]
    pub required_feedback: Option<String>,
    pub field_type: CustomFieldType,
}

/// Error messages for localization.
#[derive(Deserialize)]
#[serde(default)]
pub struct ErrorMessages {
    pub captcha_error: String,
    pub email_error: String,
}
impl Default for ErrorMessages {
    fn default() -> Self {
        Self {
            captcha_error: "You did enter the wrong code at the end of the form. Please try again."
                .to_string(),
            email_error:
                "An internal error occurred while sending your request. Please try again later."
                    .to_string(),
        }
    }
}

#[derive(Deserialize)]
#[serde(default)]
pub struct NameField {
    pub label: String,
    pub required_feedback: String,
}
impl Default for NameField {
    fn default() -> Self {
        Self {
            label: "Name".to_string(),
            required_feedback: "Please enter your name".to_string(),
        }
    }
}

#[derive(Deserialize)]
#[serde(default)]
pub struct EmailField {
    pub label: String,
    pub required_feedback: String,
}
impl Default for EmailField {
    fn default() -> Self {
        Self {
            label: "Email".to_string(),
            required_feedback: "Please enter your email".to_string(),
        }
    }
}

#[derive(Deserialize)]
#[serde(default)]
pub struct CaptchaField {
    pub label: String,
    pub required_feedback: String,
}
impl Default for CaptchaField {
    fn default() -> Self {
        Self {
            label: "Enter the code above".to_string(),
            required_feedback: "Please enter the code from the image above".to_string(),
        }
    }
}

/// Localization strings.
#[derive(Deserialize)]
#[serde(default)]
pub struct Strings {
    pub description: String,
    pub title: String,
    pub optional: String,
    pub submit: String,
    pub success: String,
    pub message_from: String,
    pub name_field: NameField,
    pub email_field: EmailField,
    pub captcha_field: CaptchaField,
    pub error_messages: ErrorMessages,
}
impl Default for Strings {
    fn default() -> Self {
        Self {
            description: String::default(),
            title: "Contact form".to_string(),
            optional: "optional".to_string(),
            submit: "Submit".to_string(),
            success: "Your request has been successfully submitted. We will get back to you soon."
                .to_string(),
            message_from: "Message from".to_string(),
            name_field: NameField::default(),
            email_field: EmailField::default(),
            captcha_field: CaptchaField::default(),
            error_messages: ErrorMessages::default(),
        }
    }
}

#[derive(Deserialize)]
pub struct StateConfig {
    /// The path prefix of all routes.
    #[serde(default = "default_path_prefix")]
    pub path_prefix: String,
    pub custom_fields: Vec<CustomField>,
    /// The language tag of the HTML file.
    #[serde(default = "default_lang")]
    pub lang: String,
    #[serde(default)]
    pub strings: Strings,
}
fn default_path_prefix() -> String {
    "/".to_string()
}
fn default_lang() -> String {
    "en".to_string()
}

/// Configuration.
#[derive(Deserialize)]
pub struct Config {
    /// The server socket address including port.
    #[serde(default = "default_socket_address")]
    pub socket_address: String,
    pub email: Email,
    #[serde(default)]
    pub utc_offset: UtcOffset,
    #[serde(flatten)]
    pub state_config: StateConfig,
}
fn default_socket_address() -> String {
    "0.0.0.0:80".to_string()
}

impl Config {
    /// Parses the configuration in the given data directory.
    pub fn build(data_dir: &Path) -> Result<Self> {
        let reader = {
            let mut buf = data_dir.to_path_buf();
            buf.push("config.yaml");

            let file = File::open(&buf).with_context(|| {
                format!("Can not open the config file at the path {}", buf.display())
            })?;

            BufReader::new(file)
        };

        let mut config: Self =
            serde_yaml::from_reader(reader).context("Can not parse the YAML config file!")?;

        // Add a space at the end for the email subject.
        config.state_config.strings.message_from =
            config.state_config.strings.message_from.trim().to_string() + " ";

        // Add the optional word to fields without a required_feedback.
        config
            .state_config
            .custom_fields
            .iter_mut()
            .filter(|field| field.required_feedback.is_none())
            .for_each(|field| {
                field.label = format!(
                    "{} ({})",
                    field.label.trim(),
                    config.state_config.strings.optional
                );
            });

        Ok(config)
    }
}