use std::path::PathBuf;

use anyhow::{anyhow, Context, Result};

/// Well-known dev JWT secret shipped in `.env.example`. If APP_ENV=production
/// we refuse to start with this value; otherwise we warn loudly.
const DEV_JWT_SECRET_SENTINEL: &str = "dev_secret_do_not_use_in_production_32byteslong_aaaa";

/// A secret is "placeholder-ish" if it's the shipped dev sentinel or still carries
/// the tell-tale scaffolding substrings from `.env.example`. Length alone is not
/// enough — the shipped `change_me_...` placeholder is >32 chars.
fn looks_placeholder(s: &str) -> bool {
    let lower = s.to_ascii_lowercase();
    s == DEV_JWT_SECRET_SENTINEL
        || lower.contains("change_me")
        || lower.contains("dev_secret")
        || lower.contains("placeholder")
}

/// Enforce secret hygiene. In production every guard is hard-fail: a booting app
/// with a publicly-known signing key is worse than one that refuses to start.
/// Outside production the dev sentinel is tolerated (warned) so local dev is frictionless.
fn validate_secrets(is_prod: bool, jwt_secret: &str, admin_password_hash: &str) -> Result<()> {
    if is_prod {
        if looks_placeholder(jwt_secret) {
            return Err(anyhow!(
                "Refusing to start in production with a placeholder JWT_SECRET — \
                 rotate it (openssl rand -hex 64)."
            ));
        }
        if jwt_secret.len() < 32 {
            return Err(anyhow!("JWT_SECRET must be at least 32 characters."));
        }
        if admin_password_hash.is_empty() || looks_placeholder(admin_password_hash) {
            return Err(anyhow!(
                "Refusing to start in production without a real ADMIN_PASSWORD_HASH — \
                 generate one (htpasswd -bnBC 12 '' <password> | tr -d ':\\n')."
            ));
        }
    } else if jwt_secret == DEV_JWT_SECRET_SENTINEL {
        tracing::warn!(
            "JWT_SECRET is the dev sentinel — fine for local development, NEVER ship this."
        );
    } else if jwt_secret.len() < 32 {
        return Err(anyhow!("JWT_SECRET must be at least 32 characters."));
    }
    Ok(())
}

#[derive(Clone, Debug)]
pub struct AppConfig {
    pub database_url: String,
    pub jwt_secret: String,
    pub session_expiry_days: i64,
    pub admin_password_hash: String,
    pub event_name: String,
    pub event_slug: String,
    pub media_path: PathBuf,
    pub app_port: u16,
}

impl AppConfig {
    pub fn from_env() -> Result<Self> {
        let app_env =
            std::env::var("APP_ENV").unwrap_or_else(|_| "development".to_string());
        let is_prod = app_env.eq_ignore_ascii_case("production");

        let jwt_secret = std::env::var("JWT_SECRET").context("JWT_SECRET must be set")?;
        let admin_password_hash = std::env::var("ADMIN_PASSWORD_HASH").unwrap_or_default();

        validate_secrets(is_prod, &jwt_secret, &admin_password_hash)?;

        Ok(Self {
            database_url: std::env::var("DATABASE_URL")
                .context("DATABASE_URL must be set")?,
            jwt_secret,
            session_expiry_days: std::env::var("SESSION_EXPIRY_DAYS")
                .unwrap_or_else(|_| "30".to_string())
                .parse()
                .context("SESSION_EXPIRY_DAYS must be a number")?,
            admin_password_hash,
            event_name: std::env::var("EVENT_NAME")
                .unwrap_or_else(|_| "EventSnap".to_string()),
            event_slug: std::env::var("EVENT_SLUG")
                .context("EVENT_SLUG must be set")?,
            media_path: PathBuf::from(
                std::env::var("MEDIA_PATH").unwrap_or_else(|_| "/media".to_string()),
            ),
            app_port: std::env::var("APP_PORT")
                .unwrap_or_else(|_| "3000".to_string())
                .parse()
                .context("APP_PORT must be a number")?,
        })
    }
}

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

    const REAL_SECRET: &str = "a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2";
    const REAL_HASH: &str = "$2y$12$abcdefghijklmnopqrstuv.wxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012";

    #[test]
    fn prod_rejects_shipped_placeholder_secret() {
        // The exact string shipped in `.env` — >32 chars, so it must be caught by
        // the substring guard, not the length check.
        let err = validate_secrets(true, "change_me_to_a_random_64_byte_hex_string", REAL_HASH);
        assert!(err.is_err(), "placeholder JWT_SECRET must be rejected in prod");
    }

    #[test]
    fn prod_rejects_dev_sentinel_and_short_secret() {
        assert!(validate_secrets(true, DEV_JWT_SECRET_SENTINEL, REAL_HASH).is_err());
        assert!(validate_secrets(true, "tooshort", REAL_HASH).is_err());
    }

    #[test]
    fn prod_rejects_missing_or_placeholder_admin_hash() {
        assert!(validate_secrets(true, REAL_SECRET, "").is_err());
        assert!(validate_secrets(true, REAL_SECRET, "$2y$12$placeholder_replace_me").is_err());
    }

    #[test]
    fn prod_accepts_real_secrets() {
        assert!(validate_secrets(true, REAL_SECRET, REAL_HASH).is_ok());
    }

    #[test]
    fn non_prod_tolerates_dev_sentinel() {
        assert!(validate_secrets(false, DEV_JWT_SECRET_SENTINEL, "").is_ok());
    }

    #[test]
    fn non_prod_still_rejects_short_non_sentinel_secret() {
        assert!(validate_secrets(false, "tooshort", "").is_err());
    }

    #[test]
    fn placeholder_detection_is_case_insensitive() {
        // looks_placeholder lowercases before matching — an upper/mixed-case
        // placeholder must still be rejected in prod.
        assert!(validate_secrets(true, "CHANGE_ME_TO_A_RANDOM_64_BYTE_HEX_STRING", REAL_HASH).is_err());
        assert!(validate_secrets(true, REAL_SECRET, "$2Y$12$PLACEHOLDER_replace_me").is_err());
    }

    #[test]
    fn prod_len_boundary_at_32() {
        // Exactly 32 non-placeholder chars is the minimum accepted; 31 is rejected.
        const LEN_32: &str = "abcdefghijklmnopqrstuvwxyz012345";
        const LEN_31: &str = "abcdefghijklmnopqrstuvwxyz01234";
        assert_eq!(LEN_32.len(), 32);
        assert_eq!(LEN_31.len(), 31);
        assert!(validate_secrets(true, LEN_32, REAL_HASH).is_ok());
        assert!(validate_secrets(true, LEN_31, REAL_HASH).is_err());
    }
}