// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.

use std::collections::BTreeMap;

use tokio_postgres::error::SqlState;

use crate::{Format, Severity};

// Pgwire protocol versions are represented as 32-bit integers, where the
// high 16 bits represent the major version and the low 16 bits represent the
// minor version.
//
// There have only been three released protocol versions, v1.0, v2.0, and v3.0.
// The protocol changes very infrequently: the most recent protocol version,
// v3.0, was released with Postgres v7.4 in 2003.
//
// Somewhat unfortunately, the protocol overloads the version field to indicate
// special types of connections, namely, SSL connections and cancellation
// connections. These pseudo-versions were constructed to avoid ever matching
// a true protocol version.

pub const VERSION_1: i32 = 0x10000;
pub const VERSION_2: i32 = 0x20000;
pub const VERSION_3: i32 = 0x30000;
pub const VERSION_CANCEL: i32 = (1234 << 16) + 5678;
pub const VERSION_SSL: i32 = (1234 << 16) + 5679;
pub const VERSION_GSSENC: i32 = (1234 << 16) + 5680;

pub const VERSIONS: &[i32] = &[
    VERSION_1,
    VERSION_2,
    VERSION_3,
    VERSION_CANCEL,
    VERSION_SSL,
    VERSION_GSSENC,
];

/// Like [`FrontendMessage`], but only the messages that can occur during
/// startup protocol negotiation.
#[derive(Debug)]
pub enum FrontendStartupMessage {
    /// Begin a connection.
    Startup {
        version: i32,
        params: BTreeMap<String, String>,
    },

    /// Request SSL encryption for the connection.
    SslRequest,

    /// Request GSSAPI encryption for the connection.
    GssEncRequest,

    /// Cancel a query that is running on another connection.
    CancelRequest {
        /// The target connection ID.
        conn_id: u32,
        /// The secret key for the target connection.
        secret_key: u32,
    },
}

/// A decoded frontend pgwire [message], representing instructions for the
/// backend.
///
/// [message]: https://www.postgresql.org/docs/11/protocol-message-formats.html
#[derive(Debug)]
pub enum FrontendMessage {
    /// Execute the specified SQL.
    ///
    /// This is issued as part of the simple query flow.
    Query {
        /// The SQL to execute.
        sql: String,
    },

    /// Parse the specified SQL into a prepared statement.
    ///
    /// This starts the extended query flow.
    Parse {
        /// The name of the prepared statement to create. An empty string
        /// specifies the unnamed prepared statement.
        name: String,
        /// The SQL to parse.
        sql: String,
        /// The OID of each parameter data type for which the client wants to
        /// prespecify types. A zero OID is equivalent to leaving the type
        /// unspecified.
        ///
        /// The number of specified parameter data types can be less than the
        /// number of parameters specified in the query.
        param_types: Vec<u32>,
    },

    /// Describe an existing prepared statement.
    ///
    /// This command is part of the extended query flow.
    DescribeStatement {
        /// The name of the prepared statement to describe.
        name: String,
    },

    /// Describe an existing portal.
    ///
    /// This command is part of the extended query flow.
    DescribePortal {
        /// The name of the portal to describe.
        name: String,
    },

    /// Bind an existing prepared statement to a portal.
    ///
    /// This command is part of the extended query flow.
    Bind {
        /// The destination portal. An empty string selects the unnamed
        /// portal. The portal can later be executed with the `Execute` command.
        portal_name: String,
        /// The source prepared statement. An empty string selects the unnamed
        /// prepared statement.
        statement_name: String,
        /// The formats used to encode the parameters in `raw_parameters`.
        param_formats: Vec<Format>,
        /// The value of each parameter, encoded using the formats described
        /// by `parameter_formats`.
        raw_params: Vec<Option<Vec<u8>>>,
        /// The desired formats for the columns in the result set.
        result_formats: Vec<Format>,
    },

    /// Execute a bound portal.
    ///
    /// This command is part of the extended query flow.
    Execute {
        /// The name of the portal to execute.
        portal_name: String,
        /// The maximum number number of rows to return before suspending.
        ///
        /// 0 or negative means infinite.
        max_rows: i32,
    },

    /// Flush any pending output.
    ///
    /// This command is part of the extended query flow.
    Flush,

    /// Finish an extended query.
    ///
    /// This command is part of the extended query flow.
    Sync,

    /// Close the named statement.
    ///
    /// This command is part of the extended query flow.
    CloseStatement {
        name: String,
    },

    /// Close the named portal.
    ///
    // This command is part of the extended query flow.
    ClosePortal {
        name: String,
    },

    /// Terminate a connection.
    Terminate,

    CopyData(Vec<u8>),

    CopyDone,

    CopyFail(String),

    Password {
        password: String,
    },
}

impl FrontendMessage {
    pub fn name(&self) -> &'static str {
        match self {
            FrontendMessage::Query { .. } => "query",
            FrontendMessage::Parse { .. } => "parse",
            FrontendMessage::DescribeStatement { .. } => "describe_statement",
            FrontendMessage::DescribePortal { .. } => "describe_portal",
            FrontendMessage::Bind { .. } => "bind",
            FrontendMessage::Execute { .. } => "execute",
            FrontendMessage::Flush => "flush",
            FrontendMessage::Sync => "sync",
            FrontendMessage::CloseStatement { .. } => "close_statement",
            FrontendMessage::ClosePortal { .. } => "close_portal",
            FrontendMessage::Terminate => "terminate",
            FrontendMessage::CopyData(_) => "copy_data",
            FrontendMessage::CopyDone => "copy_done",
            FrontendMessage::CopyFail(_) => "copy_fail",
            FrontendMessage::Password { .. } => "password",
        }
    }
}

#[derive(Debug)]
pub struct ErrorResponse {
    pub severity: Severity,
    pub code: SqlState,
    pub message: String,
    pub detail: Option<String>,
    pub hint: Option<String>,
    pub position: Option<usize>,
}

impl ErrorResponse {
    pub fn fatal<S>(code: SqlState, message: S) -> ErrorResponse
    where
        S: Into<String>,
    {
        ErrorResponse::new(Severity::Fatal, code, message)
    }

    pub fn error<S>(code: SqlState, message: S) -> ErrorResponse
    where
        S: Into<String>,
    {
        ErrorResponse::new(Severity::Error, code, message)
    }

    pub fn notice<S>(code: SqlState, message: S) -> ErrorResponse
    where
        S: Into<String>,
    {
        ErrorResponse::new(Severity::Notice, code, message)
    }

    fn new<S>(severity: Severity, code: SqlState, message: S) -> ErrorResponse
    where
        S: Into<String>,
    {
        ErrorResponse {
            severity,
            code,
            message: message.into(),
            detail: None,
            hint: None,
            position: None,
        }
    }

    pub fn with_position(mut self, position: usize) -> ErrorResponse {
        self.position = Some(position);
        self
    }
}