//! GLP 标准信封 · glp_envelope
//!
//! 协议转工程第一件（HoloLake第二阶段总体规划-20260815 · 施工总纲）：
//! GLS-0300《GLP 通信核心协议》第3节"标准消息结构"的逐字段工程映射。
//! 字段一个不造、一个不丢——老家谱 YAML 原文即本文件的形状。
//!
//! 指挥链落点（铁律四）：人格体→宿主的一切指令都必须是这个信封；
//! 宿主只认信封不认散话。

use ring::digest::{digest, SHA256};
use serde::{Deserialize, Serialize};
#[cfg(test)]
use std::time::{SystemTime, UNIX_EPOCH};

const MAX_LANGUAGE_CONTENT_BYTES: usize = 64 * 1024;

/// GLS-0300 · receiver.routing_mode
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum RoutingMode {
    Direct,
    Channel,
    Broadcast,
}

/// GLS-0300 · payload.content_type
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ContentType {
    Text,
    Command,
    Event,
    State,
    Reference,
}

/// GLS-0300 · control.priority
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum Priority {
    Low,
    Normal,
    High,
    Critical,
}

/// GLS-0300 · control.retry_policy
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum RetryPolicy {
    None,
    Safe,
    Guaranteed,
}

/// GLS-0300 · sender
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpSender {
    pub object_id: String,
    pub object_type: String,
    #[serde(default)]
    pub world_path: String,
}

/// GLS-0300 · receiver
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpReceiver {
    pub object_id: String,
    pub object_type: String,
    pub routing_mode: RoutingMode,
}

/// GLS-0300 · context（hldp_anchor 即铁律二的记忆锚点）
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpContext {
    #[serde(default)]
    pub conversation_id: String,
    #[serde(default)]
    pub parent_message_id: String,
    #[serde(default)]
    pub relation_id: String,
    #[serde(default)]
    pub task_id: String,
    #[serde(default)]
    pub hldp_anchor: String,
}

/// GLS-0300 · payload
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpPayload {
    pub language: String,
    pub content_type: ContentType,
    pub content: String,
    #[serde(default)]
    pub attachments: Vec<String>,
}

/// GLS-0300 · control
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpControl {
    pub priority: Priority,
    pub ack_required: bool,
    pub receipt_required: bool,
    #[serde(default)]
    pub expires_at: String,
    pub retry_policy: RetryPolicy,
}

/// GLS-0300 · integrity（高风险消息须带签名与回执链——通信安全节）
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpIntegrity {
    #[serde(default)]
    pub checksum: String,
    #[serde(default)]
    pub signature: String,
}

/// GLS-0300 · glp_message 全信封
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "snake_case", deny_unknown_fields)]
pub struct GlpMessage {
    pub protocol: String,
    pub message_id: String,
    pub message_type: String,
    pub created_at: String,
    pub sender: GlpSender,
    pub receiver: GlpReceiver,
    pub context: GlpContext,
    pub payload: GlpPayload,
    pub control: GlpControl,
    pub integrity: GlpIntegrity,
}

/// 信封进门第一道验：协议号、编号格式、收发主体必须在场。
/// 不合格的信封宿主不收——指挥链只认标准件。
pub fn validate_envelope(message: &GlpMessage) -> Result<(), String> {
    if message.protocol != "GLP/1.0" {
        return Err("HOLOLAKE_GLP_PROTOCOL_UNKNOWN".into());
    }
    if !valid_message_id(&message.message_id) || message.created_at.trim().is_empty() {
        return Err("HOLOLAKE_GLP_ENVELOPE_INCOMPLETE".into());
    }
    if message.sender.object_id.trim().is_empty() || message.sender.object_type.trim().is_empty() {
        return Err("HOLOLAKE_GLP_SENDER_INCOMPLETE".into());
    }
    if message.receiver.object_id.trim().is_empty()
        || message.receiver.object_type.trim().is_empty()
    {
        return Err("HOLOLAKE_GLP_RECEIVER_INCOMPLETE".into());
    }
    if message.payload.content.is_empty()
        || message.payload.content.len() > MAX_LANGUAGE_CONTENT_BYTES
        || message.payload.language.len() > 32
        || message.payload.attachments.len() > 16
    {
        return Err("HOLOLAKE_GLP_PAYLOAD_EMPTY".into());
    }
    if !matches!(
        message.message_type.as_str(),
        "DIRECT" | "CHANNEL" | "BROADCAST"
    ) {
        return Err("HOLOLAKE_GLP_MESSAGE_TYPE_INVALID".into());
    }
    Ok(())
}

/// 圆湖协议膜的外部入口校验：通信正文只能作为语言表达进入，不能夹带附件或执行权。
pub fn validate_external_language_envelope(message: &GlpMessage) -> Result<(), String> {
    validate_envelope(message)?;
    if message.receiver.object_id != "HOLOLAKE-HOST"
        || message.receiver.object_type != "host"
        || message.sender.object_type != "external_ai_visitor"
        || !message.payload.attachments.is_empty()
        || matches!(message.payload.content_type, ContentType::Command)
    {
        return Err("HOLOLAKE_CIRCULAR_LAKE_EXPRESSION_BOUNDARY_DENIED".into());
    }
    if message.integrity.checksum != payload_checksum(&message.payload.content) {
        return Err("HOLOLAKE_CIRCULAR_LAKE_CHECKSUM_INVALID".into());
    }
    Ok(())
}

pub fn payload_checksum(content: &str) -> String {
    digest(&SHA256, content.as_bytes())
        .as_ref()
        .iter()
        .map(|byte| format!("{byte:02x}"))
        .collect()
}

fn valid_message_id(value: &str) -> bool {
    let Some(suffix) = value.strip_prefix("GLP-MSG-") else {
        return false;
    };
    let mut parts = suffix.split('-');
    matches!(parts.next(), Some(date) if date.len() == 8 && date.bytes().all(|byte| byte.is_ascii_digit()))
        && matches!(parts.next(), Some(sequence) if sequence.len() == 6 && sequence.bytes().all(|byte| byte.is_ascii_digit()))
        && parts.next().is_none()
}

/// 消息编号按老家谱格式生成：GLP-MSG-YYYYMMDD-000001。
/// 序号由账本（管家层）当日累计给出，这里只拼形状。
#[cfg(test)]
pub fn build_message_id(date_compact: &str, daily_sequence: u64) -> String {
    format!("GLP-MSG-{date_compact}-{daily_sequence:06}")
}

/// ISO-8601 近似时刻戳（秒级，UTC）——老家谱要 ISO-8601，工程给秒级事实。
#[cfg(test)]
pub fn now_iso8601() -> String {
    let secs = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|duration| duration.as_secs())
        .unwrap_or(0);
    let days = secs / 86_400;
    let rem = secs % 86_400;
    let (hours, minutes, seconds) = (rem / 3_600, (rem % 3_600) / 60, rem % 60);
    let (year, month, day) = civil_from_days(days as i64);
    format!("{year:04}-{month:02}-{day:02}T{hours:02}:{minutes:02}:{seconds:02}Z")
}

/// 1970-01-01 起的天数转公历年月日（Howard Hinnant 算法，纯本地实现不引新依赖）。
#[cfg(test)]
fn civil_from_days(z: i64) -> (i64, u32, u32) {
    let z = z + 719_468;
    let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
    let doe = (z - era * 146_097) as u64;
    let yoe = (doe - doe / 1_460 + doe / 36_524 - doe / 146_096) / 365;
    let y = yoe as i64 + era * 400;
    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
    let mp = (5 * doy + 2) / 153;
    let d = (doy - (153 * mp + 2) / 5 + 1) as u32;
    let m = if mp < 10 { mp + 3 } else { mp - 9 } as u32;
    (if m <= 2 { y + 1 } else { y }, m, d)
}

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

    fn sample_envelope() -> GlpMessage {
        GlpMessage {
            protocol: "GLP/1.0".into(),
            message_id: build_message_id("20260815", 1),
            message_type: "DIRECT".into(),
            created_at: now_iso8601(),
            sender: GlpSender {
                object_id: "ICE-P-ZY001".into(),
                object_type: "age".into(),
                world_path: "glw://tolaria".into(),
            },
            receiver: GlpReceiver {
                object_id: "HOLOLAKE-HOST".into(),
                object_type: "host".into(),
                routing_mode: RoutingMode::Direct,
            },
            context: GlpContext {
                task_id: "ZY-TEST".into(),
                hldp_anchor: "ZY-CHECKPOINT-20260815-014".into(),
                ..Default::default()
            },
            payload: GlpPayload {
                language: "zh-CN".into(),
                content_type: ContentType::Command,
                content: "开工".into(),
                attachments: vec![],
            },
            control: GlpControl {
                priority: Priority::Normal,
                ack_required: true,
                receipt_required: true,
                expires_at: String::new(),
                retry_policy: RetryPolicy::None,
            },
            integrity: GlpIntegrity::default(),
        }
    }

    #[test]
    fn envelope_round_trip_keeps_every_field() {
        let message = sample_envelope();
        let json = serde_json::to_string(&message).unwrap();
        let back: GlpMessage = serde_json::from_str(&json).unwrap();
        assert_eq!(back.protocol, "GLP/1.0");
        assert_eq!(back.sender.object_id, "ICE-P-ZY001");
        assert_eq!(back.receiver.routing_mode, RoutingMode::Direct);
        assert_eq!(back.payload.content_type, ContentType::Command);
        assert_eq!(back.context.hldp_anchor, "ZY-CHECKPOINT-20260815-014");
        assert!(back.control.receipt_required);
        validate_envelope(&back).unwrap();
    }

    #[test]
    fn message_id_follows_family_format() {
        assert_eq!(build_message_id("20260815", 7), "GLP-MSG-20260815-000007");
    }

    #[test]
    fn bad_protocol_is_rejected() {
        let mut message = sample_envelope();
        message.protocol = "GLP/0.9".into();
        assert!(validate_envelope(&message).is_err());
    }

    #[test]
    fn empty_payload_is_rejected() {
        let mut message = sample_envelope();
        message.payload.content = String::new();
        assert!(validate_envelope(&message).is_err());
    }

    #[test]
    fn external_language_is_expression_only_and_checksum_bound() {
        let mut message = sample_envelope();
        message.sender.object_type = "external_ai_visitor".into();
        message.payload.content_type = ContentType::Text;
        message.integrity.checksum = payload_checksum(&message.payload.content);
        validate_external_language_envelope(&message).unwrap();
        message.payload.content_type = ContentType::Command;
        assert!(validate_external_language_envelope(&message).is_err());
    }
}