use std::fmt;
use std::time::Duration;

use remora_domain::OpaqueId;
use reqwest::redirect::Policy;
use reqwest::{Client, StatusCode};
use serde::{Deserialize, Serialize};

use crate::error::CredentialError;
use crate::types::SecretMaterial;

/// One non-destroyed KV v2 version observed via secret metadata.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct LiveVaultVersion {
    pub version: u64,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(crate) enum EmptyPathFence {
    Created(u64),
    Occupied,
}

/// Vault KV v2 access for credential secret material.
///
/// Topology and auth method are deployment choices. This client accepts a token
/// (fixture root token or workload token after Kubernetes auth) and never logs
/// request or response bodies that contain secret material.
#[derive(Clone)]
pub struct VaultConfig {
    pub address: String,
    pub token: String,
    /// KV v2 mount, e.g. `secret`.
    pub mount: String,
    /// Path prefix under the mount where this deployment may allocate secrets.
    pub path_prefix: String,
    pub timeout: Duration,
}

impl fmt::Debug for VaultConfig {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("VaultConfig")
            .field("address", &self.address)
            .field("mount", &self.mount)
            .field("path_prefix", &self.path_prefix)
            .field("timeout", &self.timeout)
            .field("token", &"REDACTED")
            .finish()
    }
}

impl VaultConfig {
    pub fn from_env() -> Result<Self, CredentialError> {
        let address = required_env("REMORA_VAULT_ADDR")?;
        let token = required_env("REMORA_VAULT_TOKEN")?;
        let full_path = required_env("REMORA_VAULT_PATH")?;
        let (mount, path_prefix) = split_vault_path(&full_path)?;
        Ok(Self {
            address,
            token,
            mount,
            path_prefix,
            timeout: Duration::from_secs(10),
        })
    }

    #[must_use]
    pub fn with_timeout(mut self, timeout: Duration) -> Self {
        self.timeout = timeout;
        self
    }

    /// Allocate the opaque secret path for one credential version identity.
    #[must_use]
    pub fn secret_path_for(&self, credential_id: &OpaqueId, version_id: &OpaqueId) -> String {
        format!(
            "{}/versions/{}",
            self.credential_path_for(credential_id),
            version_id.as_str()
        )
    }

    #[must_use]
    pub fn credential_path_for(&self, credential_id: &OpaqueId) -> String {
        if self.path_prefix.is_empty() {
            format!("credentials/{}", credential_id.as_str())
        } else {
            format!(
                "{}/credentials/{}",
                self.path_prefix.trim_matches('/'),
                credential_id.as_str()
            )
        }
    }
}

#[derive(Clone)]
pub struct VaultClient {
    http: Client,
    config: VaultConfig,
}

impl fmt::Debug for VaultClient {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("VaultClient")
            .field("config", &self.config)
            .finish()
    }
}

impl VaultClient {
    pub fn new(config: VaultConfig) -> Result<Self, CredentialError> {
        // Disable redirects and ambient proxy discovery so X-Vault-Token and
        // secret write bodies cannot leave the configured Vault endpoint via
        // hop rewriting or HTTP_PROXY/HTTPS_PROXY injection.
        let http = Client::builder()
            .timeout(config.timeout)
            .redirect(Policy::none())
            .no_proxy()
            .build()
            .map_err(|error| {
                CredentialError::Config(format!("failed to build vault HTTP client: {error}"))
            })?;
        Ok(Self { http, config })
    }

    #[must_use]
    pub fn config(&self) -> &VaultConfig {
        &self.config
    }

    /// Create secret material and return the immutable KV v2 version number.
    ///
    /// The write uses CAS 0 so an existing intent-bound path is never overwritten.
    pub async fn put_version(
        &self,
        mount: &str,
        secret_path: &str,
        material: &SecretMaterial,
    ) -> Result<u64, CredentialError> {
        let url = format!(
            "{}/v1/{}/data/{}",
            self.config.address.trim_end_matches('/'),
            mount.trim_matches('/'),
            secret_path.trim_start_matches('/')
        );
        let body = KvWriteRequest {
            data: material.clone(),
            options: KvWriteOptions { cas: 0 },
        };
        let response = self
            .http
            .post(&url)
            .header("X-Vault-Token", &self.config.token)
            .json(&body)
            .send()
            .await
            .map_err(map_transport)?;
        let status = response.status();
        if !status.is_success() {
            let _ = response.bytes().await;
            return Err(map_http_status(status, "write secret version"));
        }
        let parsed: KvWriteResponse = response.json().await.map_err(map_transport)?;
        let version = parsed.data.and_then(|data| data.version).ok_or_else(|| {
            CredentialError::Config("vault write response omitted version".into())
        })?;
        if version < 1 {
            return Err(CredentialError::Config(
                "vault returned non-positive secret version".into(),
            ));
        }
        Ok(version)
    }

    pub(crate) async fn fence_empty_path(
        &self,
        mount: &str,
        secret_path: &str,
    ) -> Result<EmptyPathFence, CredentialError> {
        let url = format!(
            "{}/v1/{}/data/{}",
            self.config.address.trim_end_matches('/'),
            mount.trim_matches('/'),
            secret_path.trim_start_matches('/')
        );
        let response = self
            .http
            .post(&url)
            .header("X-Vault-Token", &self.config.token)
            .json(&FenceWriteRequest {
                data: FenceMarker {
                    remora_write_fence: true,
                },
                options: KvWriteOptions { cas: 0 },
            })
            .send()
            .await
            .map_err(map_transport)?;
        let status = response.status();
        if status == StatusCode::BAD_REQUEST {
            let _ = response.bytes().await;
            return Ok(EmptyPathFence::Occupied);
        }
        if !status.is_success() {
            let _ = response.bytes().await;
            return Err(map_http_status(status, "fence empty secret path"));
        }
        let parsed: KvWriteResponse = response.json().await.map_err(map_transport)?;
        let version = parsed.data.and_then(|data| data.version).ok_or_else(|| {
            CredentialError::Config("vault fence response omitted version".into())
        })?;
        if version < 1 {
            return Err(CredentialError::Config(
                "vault returned non-positive fence version".into(),
            ));
        }
        Ok(EmptyPathFence::Created(version))
    }

    /// Read one exact KV v2 version. Missing or destroyed versions fail closed.
    pub async fn get_version(
        &self,
        mount: &str,
        secret_path: &str,
        vault_kv_version: u64,
    ) -> Result<SecretMaterial, CredentialError> {
        let url = format!(
            "{}/v1/{}/data/{}?version={vault_kv_version}",
            self.config.address.trim_end_matches('/'),
            mount.trim_matches('/'),
            secret_path.trim_start_matches('/')
        );
        let response = self
            .http
            .get(&url)
            .header("X-Vault-Token", &self.config.token)
            .send()
            .await
            .map_err(map_transport)?;
        let status = response.status();
        if status == StatusCode::NOT_FOUND {
            let _ = response.bytes().await;
            return Err(CredentialError::Unresolvable);
        }
        if !status.is_success() {
            let _ = response.bytes().await;
            return Err(map_http_status(status, "read secret version"));
        }
        let parsed: KvReadResponse = response.json().await.map_err(map_transport)?;
        let data = parsed.data.ok_or(CredentialError::Unresolvable)?;
        let material = data.data.ok_or(CredentialError::Unresolvable)?;
        let reported = data
            .metadata
            .and_then(|meta| meta.version)
            .ok_or(CredentialError::Unresolvable)?;
        if reported != vault_kv_version {
            return Err(CredentialError::Unresolvable);
        }
        material.validate()?;
        Ok(material)
    }

    /// List non-destroyed KV v2 versions present at a path (for intent recovery).
    ///
    pub async fn list_live_versions(
        &self,
        mount: &str,
        secret_path: &str,
    ) -> Result<Vec<LiveVaultVersion>, CredentialError> {
        let url = format!(
            "{}/v1/{}/metadata/{}",
            self.config.address.trim_end_matches('/'),
            mount.trim_matches('/'),
            secret_path.trim_start_matches('/')
        );
        let response = self
            .http
            .get(&url)
            .header("X-Vault-Token", &self.config.token)
            .send()
            .await
            .map_err(map_transport)?;
        let status = response.status();
        if status == StatusCode::NOT_FOUND {
            let _ = response.bytes().await;
            return Ok(Vec::new());
        }
        if !status.is_success() {
            let _ = response.bytes().await;
            return Err(map_http_status(status, "list secret metadata"));
        }
        let parsed: KvMetadataResponse = response.json().await.map_err(map_transport)?;
        let versions = parsed
            .data
            .and_then(|data| data.versions)
            .unwrap_or_default();
        let mut live = Vec::new();
        for (key, meta) in versions {
            if meta.destroyed.unwrap_or(false) {
                continue;
            }
            let Ok(version) = key.parse::<u64>() else {
                continue;
            };
            if version < 1 {
                continue;
            }
            live.push(LiveVaultVersion { version });
        }
        live.sort_by_key(|entry| entry.version);
        Ok(live)
    }

    /// Irreversibly destroy one KV v2 version.
    pub async fn destroy_version(
        &self,
        mount: &str,
        secret_path: &str,
        vault_kv_version: u64,
    ) -> Result<(), CredentialError> {
        let url = format!(
            "{}/v1/{}/destroy/{}",
            self.config.address.trim_end_matches('/'),
            mount.trim_matches('/'),
            secret_path.trim_start_matches('/')
        );
        let body = DestroyRequest {
            versions: vec![vault_kv_version],
        };
        let response = self
            .http
            .post(&url)
            .header("X-Vault-Token", &self.config.token)
            .json(&body)
            .send()
            .await
            .map_err(map_transport)?;
        let status = response.status();
        if !status.is_success() {
            let _ = response.bytes().await;
            return Err(map_http_status(status, "destroy secret version"));
        }
        let _ = response.bytes().await;
        Ok(())
    }
}

#[derive(Serialize)]
struct KvWriteRequest {
    data: SecretMaterial,
    options: KvWriteOptions,
}

#[derive(Serialize)]
struct KvWriteOptions {
    cas: u8,
}

#[derive(Serialize)]
struct FenceWriteRequest {
    data: FenceMarker,
    options: KvWriteOptions,
}

#[derive(Serialize)]
struct FenceMarker {
    remora_write_fence: bool,
}

#[derive(Deserialize)]
struct KvWriteResponse {
    data: Option<KvWriteData>,
}

#[derive(Deserialize)]
struct KvWriteData {
    version: Option<u64>,
}

#[derive(Deserialize)]
struct KvReadResponse {
    data: Option<KvReadData>,
}

#[derive(Deserialize)]
struct KvReadData {
    data: Option<SecretMaterial>,
    metadata: Option<KvMetadata>,
}

#[derive(Deserialize)]
struct KvMetadata {
    version: Option<u64>,
}

#[derive(Deserialize)]
struct KvMetadataResponse {
    data: Option<KvMetadataListData>,
}

#[derive(Deserialize)]
struct KvMetadataListData {
    versions: Option<std::collections::BTreeMap<String, KvVersionMeta>>,
}

#[derive(Deserialize)]
struct KvVersionMeta {
    destroyed: Option<bool>,
}

#[derive(Serialize)]
struct DestroyRequest {
    versions: Vec<u64>,
}

fn required_env(name: &str) -> Result<String, CredentialError> {
    std::env::var(name)
        .ok()
        .filter(|value| !value.is_empty())
        .ok_or_else(|| CredentialError::Config(format!("{name} is required")))
}

/// Split a fixture path such as `secret/remora/lane-0` into mount + prefix.
pub fn split_vault_path(full: &str) -> Result<(String, String), CredentialError> {
    let trimmed = full.trim().trim_matches('/');
    if trimmed.is_empty() {
        return Err(CredentialError::Config(
            "REMORA_VAULT_PATH must include a mount".into(),
        ));
    }
    match trimmed.split_once('/') {
        Some((mount, prefix)) if !mount.is_empty() => {
            Ok((mount.to_owned(), prefix.trim_matches('/').to_owned()))
        }
        Some(_) | None => Ok((trimmed.to_owned(), String::new())),
    }
}

fn map_transport(_error: reqwest::Error) -> CredentialError {
    CredentialError::SecretStoreUnavailable
}

fn map_http_status(status: StatusCode, operation: &str) -> CredentialError {
    if status.is_server_error() || status == StatusCode::SERVICE_UNAVAILABLE {
        CredentialError::SecretStoreUnavailable
    } else if status == StatusCode::FORBIDDEN || status == StatusCode::UNAUTHORIZED {
        // Treat policy denials as unresolvable rather than leaking store details.
        CredentialError::Unresolvable
    } else if status == StatusCode::NOT_FOUND {
        CredentialError::Unresolvable
    } else {
        CredentialError::Config(format!(
            "vault {operation} failed with HTTP {}",
            status.as_u16()
        ))
    }
}