use lettre::message::Mailbox;
use std::{collections::HashMap, env, net::IpAddr, path::Path};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AuthorizationType {
    Local,
    Ldap,
    Ad,
}

impl AuthorizationType {
    fn from_values(values: &ConfigValues) -> Result<Self, Box<dyn std::error::Error>> {
        match values.get("AUTHORIZATION_TYPE", "local").trim().to_ascii_lowercase().as_str() {
            "local" => Ok(Self::Local),
            "ldap" => Ok(Self::Ldap),
            "ad" => Ok(Self::Ad),
            _ => Err("AUTHORIZATION_TYPE must be one of: local, ldap, ad".into()),
        }
    }

    pub fn as_str(self) -> &'static str {
        match self {
            Self::Local => "local",
            Self::Ldap => "ldap",
            Self::Ad => "ad",
        }
    }
}

#[derive(Debug, Clone)]
pub struct Config {
    pub host: IpAddr,
    pub port: u16,
    pub database_url: String,
    pub database_max_connections: u32,
    pub static_dir: String,
    pub files_dir: String,
    pub storage: crate::storage::StorageConfig,
    pub upload_max_size_bytes: usize,
    pub asset_version: String,
    pub asset_cache_max_age_seconds: u64,
    pub file_cache_max_age_seconds: u64,
    pub smtp: Option<crate::state::SmtpConfig>,
    pub registration_enabled: bool,
    pub account_confirmation_required: bool,
    pub share_confirmation_required: bool,
    pub frontend_log_level: String,
    pub anonymous_access_token_ttl_days: i64,
    pub user_session_ttl_days: i64,
    pub unconfirmed_account_ttl_days: i64,
    pub authorization_type: AuthorizationType,
    pub ldap: Option<crate::auth::ldap::LdapConfig>,
}

impl Config {
    pub fn load(path: Option<&Path>) -> Result<Self, Box<dyn std::error::Error>> {
        let values = ConfigValues::load(path)?;
        let host = values.get("APP_HOST", "127.0.0.1").parse()?;
        let port = values.get("APP_PORT", "3000").parse()?;
        let database_max_connections = values.get("DATABASE_MAX_CONNECTIONS", "8").parse()?;
        let upload_max_size_mb: usize = values.get("UPLOAD_MAX_SIZE_MB", "20").parse()?;
        let anonymous_access_token_ttl_days = values.positive_i64("ANONYMOUS_ACCESS_TOKEN_TTL_DAYS", 7)?;
        let user_session_ttl_days = values.positive_i64("USER_SESSION_TTL_DAYS", 3)?;
        let unconfirmed_account_ttl_days = values.positive_i64("UNCONFIRMED_ACCOUNT_TTL_DAYS", 3)?;
        let files_dir = values.get("FILES_DIR", "data/files");

        let storage = match values.get("STORAGE_DRIVER", "local").trim().to_ascii_lowercase().as_str() {
            "local" => crate::storage::StorageConfig::Local { root: files_dir.clone().into() },
            "s3" => crate::storage::StorageConfig::S3 {
                endpoint: values.optional("S3_ENDPOINT"),
                region: values.get("S3_REGION", "us-east-1"),
                bucket: values.required("S3_BUCKET", "STORAGE_DRIVER=s3")?,
                access_key: values.required("S3_ACCESS_KEY", "STORAGE_DRIVER=s3")?,
                secret_key: values.required("S3_SECRET_KEY", "STORAGE_DRIVER=s3")?,
                force_path_style: values.bool("S3_FORCE_PATH_STYLE", false)?,
            },
            _ => return Err("STORAGE_DRIVER must be local or s3".into()),
        };

        if upload_max_size_mb == 0 {
            return Err("UPLOAD_MAX_SIZE_MB must be greater than 0".into());
        }

        let authorization_type = AuthorizationType::from_values(&values)?;
        let ldap = match authorization_type {
            AuthorizationType::Local => None,
            AuthorizationType::Ldap | AuthorizationType::Ad => {
                let context = format!("AUTHORIZATION_TYPE={}", authorization_type.as_str());
                let (default_filter, default_username_attribute) = match authorization_type {
                    AuthorizationType::Ldap => ("(uid={username})", "uid"),
                    AuthorizationType::Ad => ("(|(sAMAccountName={username})(userPrincipalName={username}))", "sAMAccountName"),
                    AuthorizationType::Local => unreachable!(),
                };
                Some(crate::auth::ldap::LdapConfig {
                    url: values.required("LDAP_URL", &context)?,
                    starttls: values.bool("LDAP_STARTTLS", false)?,
                    bind_dn: values.get("LDAP_BIND_DN", ""),
                    bind_password: values.get("LDAP_BIND_PASSWORD", ""),
                    base_dn: values.required("LDAP_BASE_DN", &context)?,
                    user_filter: values.get("LDAP_USER_FILTER", default_filter),
                    username_attribute: values.get("LDAP_USERNAME_ATTRIBUTE", default_username_attribute),
                    email_attribute: values.get("LDAP_EMAIL_ATTRIBUTE", "mail"),
                    display_name_attribute: values.get("LDAP_DISPLAY_NAME_ATTRIBUTE", "displayName"),
                    external_id_attribute: values.get("LDAP_EXTERNAL_ID_ATTRIBUTE", match authorization_type {
                        AuthorizationType::Ldap => "entryUUID",
                        AuthorizationType::Ad => "objectGUID",
                        AuthorizationType::Local => unreachable!(),
                    }),
                    organization: values.get("LDAP_ORGANIZATION", "organization"),
                    provider: authorization_type.as_str().to_owned(),
                    email_required: values.bool("LDAP_EMAIL_REQUIRED", true)?,
                    link_existing_by_email: values.bool("LDAP_LINK_EXISTING_BY_EMAIL", false)?,
                    tls_verify: values.bool("LDAP_TLS_VERIFY", true)?,
                    connect_timeout_seconds: values.positive_u64("LDAP_CONNECT_TIMEOUT_SECONDS", 5)?,
                    operation_timeout_seconds: values.positive_u64("LDAP_OPERATION_TIMEOUT_SECONDS", 10)?,
                })
            }
        };

        let smtp = if let Some(host) = values.optional("SMTP_HOST") {
            Some(crate::state::SmtpConfig {
                host,
                port: values.get("SMTP_PORT", "587").parse()?,
                username: values.get("SMTP_USERNAME", ""),
                password: values.get("SMTP_PASSWORD", ""),
                from: normalize_smtp_from(
                    values.required("SMTP_FROM", "SMTP_HOST is set")?,
                )?,
                public_url: values.required("PUBLIC_URL", "SMTP_HOST is set")?,
            })
        } else {
            None
        };

        let config = Self {
            host,
            port,
            database_url: values.get("DATABASE_URL", "sqlite:///data/db/rustpad.db?mode=rwc"),
            database_max_connections,
            static_dir: values.get("STATIC_DIR", "static"),
            files_dir,
            storage,
            upload_max_size_bytes: upload_max_size_mb.checked_mul(1024 * 1024).ok_or("UPLOAD_MAX_SIZE_MB is too large")?,
            asset_version: env!("CARGO_PKG_VERSION").to_owned(),
            asset_cache_max_age_seconds: values.nonnegative_u64("ASSET_CACHE_MAX_AGE_SECONDS", 600)?,
            file_cache_max_age_seconds: values.nonnegative_u64("FILE_CACHE_MAX_AGE_SECONDS", 600)?,
            smtp,
            registration_enabled: values.bool("REGISTRATION_ENABLED", false)?,
            account_confirmation_required: values.bool("ACCOUNT_CONFIRMATION_REQUIRED", false)?,
            share_confirmation_required: values.bool("SHARE_CONFIRMATION_REQUIRED", false)?,
            frontend_log_level: values.log_level("FRONTEND_LOG_LEVEL", "warn")?,
            anonymous_access_token_ttl_days,
            user_session_ttl_days,
            unconfirmed_account_ttl_days,
            authorization_type,
            ldap,
        };
        config.validate()?;
        Ok(config)
    }

    fn validate(&self) -> Result<(), Box<dyn std::error::Error>> {
        if !(self.database_url.starts_with("sqlite:")
            || self.database_url.starts_with("postgres:")
            || self.database_url.starts_with("postgresql:")
            || self.database_url.starts_with("mysql:"))
        {
            return Err("DATABASE_URL must use sqlite, postgres/postgresql, or mysql".into());
        }
        if self.database_max_connections == 0 {
            return Err("DATABASE_MAX_CONNECTIONS must be greater than 0".into());
        }
        if self.static_dir.trim().is_empty() || self.files_dir.trim().is_empty() {
            return Err("STATIC_DIR and FILES_DIR cannot be empty".into());
        }
        if let Some(smtp) = &self.smtp {
            smtp.from
                .parse::<Mailbox>()
                .map_err(|error| format!("SMTP_FROM is not a valid mailbox: {error}"))?;
            if !(smtp.public_url.starts_with("http://") || smtp.public_url.starts_with("https://")) {
                return Err("PUBLIC_URL must start with http:// or https://".into());
            }
        }
        Ok(())
    }
}



fn normalize_smtp_from(value: String) -> Result<String, Box<dyn std::error::Error>> {
    let trimmed = value.trim();
    if trimmed.is_empty() {
        return Err("SMTP_FROM cannot be empty".into());
    }

    if trimmed.parse::<Mailbox>().is_ok() {
        return Ok(trimmed.to_owned());
    }

    let unquoted = match (trimmed.as_bytes().first(), trimmed.as_bytes().last()) {
        (Some(b'"'), Some(b'"')) | (Some(b'\''), Some(b'\'')) if trimmed.len() >= 2 => {
            trimmed[1..trimmed.len() - 1].trim()
        }
        _ => {
            return Err(format!("SMTP_FROM is not a valid mailbox: {trimmed}").into());
        }
    };

    if unquoted.is_empty() {
        return Err("SMTP_FROM cannot be empty".into());
    }

    unquoted
        .parse::<Mailbox>()
        .map_err(|error| format!("SMTP_FROM is not a valid mailbox: {error}"))?;

    Ok(unquoted.to_owned())
}

const KNOWN_CONFIG_KEYS: &[&str] = &[
    "APP_HOST", "APP_PORT", "DATABASE_URL", "DATABASE_MAX_CONNECTIONS",
    "STATIC_DIR", "FILES_DIR", "STORAGE_DRIVER", "UPLOAD_MAX_SIZE_MB",
    "ASSET_CACHE_MAX_AGE_SECONDS", "FILE_CACHE_MAX_AGE_SECONDS",
    "REGISTRATION_ENABLED", "ACCOUNT_CONFIRMATION_REQUIRED", "SHARE_CONFIRMATION_REQUIRED",
    "FRONTEND_LOG_LEVEL", "ANONYMOUS_ACCESS_TOKEN_TTL_DAYS", "USER_SESSION_TTL_DAYS",
    "UNCONFIRMED_ACCOUNT_TTL_DAYS", "AUTHORIZATION_TYPE",
    "S3_ENDPOINT", "S3_REGION", "S3_BUCKET", "S3_ACCESS_KEY", "S3_SECRET_KEY",
    "S3_FORCE_PATH_STYLE", "SMTP_HOST", "SMTP_PORT", "SMTP_USERNAME", "SMTP_PASSWORD",
    "SMTP_FROM", "PUBLIC_URL", "LDAP_URL", "LDAP_STARTTLS", "LDAP_BIND_DN",
    "LDAP_BIND_PASSWORD", "LDAP_BASE_DN", "LDAP_USER_FILTER", "LDAP_USERNAME_ATTRIBUTE",
    "LDAP_EMAIL_ATTRIBUTE", "LDAP_DISPLAY_NAME_ATTRIBUTE", "LDAP_EXTERNAL_ID_ATTRIBUTE",
    "LDAP_ORGANIZATION", "LDAP_EMAIL_REQUIRED", "LDAP_LINK_EXISTING_BY_EMAIL",
    "LDAP_TLS_VERIFY", "LDAP_CONNECT_TIMEOUT_SECONDS", "LDAP_OPERATION_TIMEOUT_SECONDS",
];

#[derive(Default)]
struct ConfigValues {
    file: HashMap<String, String>,
}

impl ConfigValues {
    fn load(path: Option<&Path>) -> Result<Self, Box<dyn std::error::Error>> {
        let Some(path) = path else { return Ok(Self::default()); };
        let content = std::fs::read_to_string(path)
            .map_err(|error| format!("cannot read config file {}: {error}", path.display()))?;
        let file = parse_yaml_config(&content)
            .map_err(|error| format!("invalid YAML in {}: {error}", path.display()))?;
        for key in file.keys() {
            if !KNOWN_CONFIG_KEYS.contains(&key.as_str()) {
                return Err(format!("unknown configuration key: {key}").into());
            }
        }
        Ok(Self { file })
    }

    fn get(&self, name: &str, default: &str) -> String {
        env::var(name).ok().or_else(|| self.file.get(name).cloned()).unwrap_or_else(|| default.to_owned())
    }

    fn optional(&self, name: &str) -> Option<String> {
        env::var(name).ok().or_else(|| self.file.get(name).cloned()).filter(|value| !value.trim().is_empty())
    }

    fn required(&self, name: &str, context: &str) -> Result<String, Box<dyn std::error::Error>> {
        self.optional(name).ok_or_else(|| format!("{name} is required when {context}").into())
    }

    fn bool(&self, name: &str, default: bool) -> Result<bool, Box<dyn std::error::Error>> {
        match self.get(name, if default { "true" } else { "false" }).trim().to_ascii_lowercase().as_str() {
            "1" | "true" | "yes" | "on" => Ok(true),
            "0" | "false" | "no" | "off" => Ok(false),
            _ => Err(format!("{name} must be true or false").into()),
        }
    }

    fn log_level(&self, name: &str, default: &str) -> Result<String, Box<dyn std::error::Error>> {
        let value = self.get(name, default).trim().to_ascii_lowercase();
        match value.as_str() {
            "off" | "error" | "warn" | "info" | "debug" => Ok(value),
            _ => Err(format!("{name} must be one of: off, error, warn, info, debug").into()),
        }
    }

    fn positive_i64(&self, name: &str, default: i64) -> Result<i64, Box<dyn std::error::Error>> {
        let value: i64 = self.get(name, &default.to_string()).parse().map_err(|_| format!("{name} must be an integer"))?;
        if value <= 0 { return Err(format!("{name} must be greater than 0").into()); }
        Ok(value)
    }

    fn positive_u64(&self, name: &str, default: u64) -> Result<u64, Box<dyn std::error::Error>> {
        let value: u64 = self.get(name, &default.to_string()).parse().map_err(|_| format!("{name} must be a non-negative integer"))?;
        if value == 0 { return Err(format!("{name} must be greater than 0").into()); }
        Ok(value)
    }

    fn nonnegative_u64(&self, name: &str, default: u64) -> Result<u64, Box<dyn std::error::Error>> {
        self.get(name, &default.to_string()).parse().map_err(|_| format!("{name} must be a non-negative integer").into())
    }
}

fn parse_yaml_config(content: &str) -> Result<HashMap<String, String>, String> {
    let mut output = HashMap::new();
    let mut sections: Vec<(usize, String)> = Vec::new();

    for (index, original) in content.lines().enumerate() {
        let line_number = index + 1;
        if original.contains('\t') {
            return Err(format!("line {line_number}: tabs are not allowed for indentation"));
        }
        let without_comment = strip_yaml_comment(original);
        if without_comment.trim().is_empty() || without_comment.trim() == "---" {
            continue;
        }
        let indent = without_comment.len() - without_comment.trim_start().len();
        let line = without_comment.trim();
        let (raw_key, raw_value) = line
            .split_once(':')
            .ok_or_else(|| format!("line {line_number}: expected key: value"))?;
        let key = raw_key.trim();
        if key.is_empty() || !key.chars().all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-') {
            return Err(format!("line {line_number}: invalid key {key:?}"));
        }
        while sections.last().is_some_and(|(section_indent, _)| *section_indent >= indent) {
            sections.pop();
        }
        let normalized = key.to_ascii_uppercase().replace('-', "_");
        let value = raw_value.trim();
        if value.is_empty() {
            sections.push((indent, normalized));
            continue;
        }
        if matches!(value.chars().next(), Some('[' | '{' | '|' | '>' | '&' | '*' | '!')) {
            return Err(format!("line {line_number}: only scalar values and nested mappings are supported"));
        }
        let mut path: Vec<&str> = sections.iter().map(|(_, key)| key.as_str()).collect();
        path.push(&normalized);
        let full_key = path.join("_");
        let parsed_value = parse_yaml_scalar(value)
            .map_err(|error| format!("line {line_number}: {error}"))?;
        if output.insert(full_key.clone(), parsed_value).is_some() {
            return Err(format!("line {line_number}: duplicate key {full_key}"));
        }
    }
    Ok(output)
}

fn strip_yaml_comment(line: &str) -> &str {
    let mut single = false;
    let mut double = false;
    let mut escaped = false;
    for (index, character) in line.char_indices() {
        if escaped {
            escaped = false;
            continue;
        }
        match character {
            '\\' if double => escaped = true,
            '\'' if !double => single = !single,
            '"' if !single => double = !double,
            '#' if !single && !double => return &line[..index],
            _ => {}
        }
    }
    line
}

fn parse_yaml_scalar(value: &str) -> Result<String, String> {
    if value.starts_with('"') {
        if !value.ends_with('"') || value.len() < 2 {
            return Err("unterminated double-quoted value".to_owned());
        }
        return serde_json::from_str::<String>(value)
            .map_err(|error| format!("invalid double-quoted value: {error}"));
    }
    if value.starts_with('\'') {
        if !value.ends_with('\'') || value.len() < 2 {
            return Err("unterminated single-quoted value".to_owned());
        }
        return Ok(value[1..value.len() - 1].replace("''", "'"));
    }
    if value.eq_ignore_ascii_case("null") || value == "~" {
        return Ok(String::new());
    }
    Ok(value.to_owned())
}


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

    #[test]
    fn smtp_from_accepts_unquoted_value() {
        assert_eq!(
            normalize_smtp_from("RustPad <rustpad@notes.example>".to_owned()).unwrap(),
            "RustPad <rustpad@notes.example>"
        );
    }

    #[test]
    fn smtp_from_removes_matching_double_quotes() {
        assert_eq!(
            normalize_smtp_from(" \"RustPad <rustpad@notes.example>\" ".to_owned()).unwrap(),
            "RustPad <rustpad@notes.example>"
        );
    }

    #[test]
    fn smtp_from_removes_matching_single_quotes() {
        assert_eq!(
            normalize_smtp_from(" 'RustPad <rustpad@notes.example>' ".to_owned()).unwrap(),
            "RustPad <rustpad@notes.example>"
        );
    }

    #[test]
    fn smtp_from_preserves_valid_quoted_display_name() {
        assert_eq!(
            normalize_smtp_from("\"Rust, Pad\" <rustpad@notes.example>".to_owned()).unwrap(),
            "\"Rust, Pad\" <rustpad@notes.example>"
        );
    }

    #[test]
    fn smtp_from_rejects_unmatched_quotes() {
        assert!(normalize_smtp_from("\"RustPad <rustpad@notes.example>".to_owned()).is_err());
    }

    #[test]
    fn smtp_from_rejects_invalid_mailbox() {
        assert!(normalize_smtp_from("RustPad".to_owned()).is_err());
    }
}