package discord_interactions

import "core:crypto/ed25519"
import "core:encoding/hex"
import "core:encoding/json"
import "core:fmt"
import "core:io"
import "core:log"
import "core:net"
import "core:os"
import REST "../discord/rest"
import http "../odin-http"
import "../odin-http/client"

Interaction :: REST.Interaction
Payload :: REST.Payload
Webhook_Payload :: REST.Webhook_Payload

ReqResPair :: struct {
    req: ^http.Request,
    res: ^http.Response,
}

Config :: struct {
    token:                string,
    port:                 int,
    interaction_endpoint: string,
}

State :: struct {
    config:           Config,
    application:      REST.Application,
    command_handlers: map[string]Command_Handler,
}

Command_Handler :: #type proc(interaction: Interaction) -> Payload

Error :: union {
    os.Error,
    json.Error,
    json.Unmarshal_Error,
    client.Error,
    client.Body_Error,
}

DISCORD_API :: "https://discord.com/api/v10"

state: State

load_config :: proc(filename: string) -> Error {
    config_bytes, config_read_err := os.read_entire_file_or_err("config.json")
    if config_read_err != nil {
        return config_read_err
    }

    json.unmarshal(config_bytes, &state.config) or_return

    headers: http.Headers
    http.headers_set(&headers, "Authorization", fmt.tprint("Bot", state.config.token))

    request: client.Request
    client.request_init(&request, .Get)
    defer client.request_destroy(&request)
    request.headers = headers

    res, res_err := client.request(&request, DISCORD_API + "/applications/@me")
    if res_err != nil {
        return res_err
    }

    body, was_alloc, body_err := client.response_body(&res)
    if body_err != nil {
        return body_err
    }

    #partial switch v in body {
    case client.Body_Plain:
        json.unmarshal(transmute([]u8)v, &state.application) or_return
    }

    return nil
}

serve :: proc() -> net.Network_Error {
    s: http.Server
    http.server_shutdown_on_interrupt(&s)

    router: http.Router
    http.router_init(&router)
    defer http.router_destroy(&router)

    http.route_post(&router, state.config.interaction_endpoint, http.handler(interactions))

    routed := http.router_handler(&router)

    port := state.config.port == 0 ? 8080 : state.config.port
    log.infof("Listening at http://{}:{}", net.address_to_string(net.IP4_Loopback), port)
    http.listen_and_serve(&s, routed, net.Endpoint{address = net.IP4_Loopback, port = port}) or_return

    return nil
}

register_command :: proc(command_name: string, handler: Command_Handler) {
    state.command_handlers[command_name] = handler
}

@(private)
interactions :: proc(req: ^http.Request, res: ^http.Response) {
    pair := new(ReqResPair)
    pair.req = req
    pair.res = res
    http.headers_set_close(&res.headers)

    http.body(req, -1, pair, proc(userdata: rawptr, body: http.Body, err: http.Body_Error) {
        reqres := cast(^ReqResPair)userdata
        req := reqres.req
        res := reqres.res

        interaction: Interaction
        json.unmarshal(transmute([]u8)body, &interaction)

        signature, signature_ok := hex.decode(
            transmute([]u8)http.headers_get(req.headers, "X-Signature-Ed25519"),
        )
        if !signature_ok {
            log.error("Failed to decode signature")
            return
        }

        timestamp := http.headers_get(req.headers, "X-Signature-Timestamp")

        ed25519_public_key: ed25519.Public_Key
        public_key_bytes, public_key_ok := hex.decode(transmute([]u8)state.application.verify_key)
        if !public_key_ok {
            log.error("Failed to decode public key")
            return
        }

        ed25519.public_key_set_bytes(&ed25519_public_key, public_key_bytes)
        if !ed25519.verify(
            &ed25519_public_key,
            transmute([]u8)fmt.tprintf("{}{}", timestamp, body),
            signature,
        ) {
            http.respond_with_status(res, .Unauthorized)
            return
        }

        switch interaction.type {
        case 1:
            if err := http.respond_json(res, Payload{type = 1}); err != nil {
                log.error("Failed to marshal payload:", err)
            }
            return
        case 2:
            handler, found := state.command_handlers[interaction.data.name]
            if found {
                if err := http.respond_json(res, handler(interaction)); err != nil {
                    log.error("Failed to marshal payload:", err)
                }
            } else {
                log.debug("Skipping unrecognized command:", interaction.data.name)
            }
            return
        }
    })
}