lib.sh

#!/bin/bash
set -euo pipefail

MATTERMOST_URL="http://mattermost.qwant.loc"
MATTERMOST_API_URL="$MATTERMOST_URL/api/v4"

header_file=/tmp/header
body_file=/tmp/body

function request # ENDPOINT CURL_ARGUMENTS...
{
    eval local url=$(sed -E 's|:(\w+)|${\1}|g' <<< "${MATTERMOST_API_URL}${FUNCNAME[1]}")

    (
        set -x
        curl --output "$body_file" \
             --dump-header "$header_file" \
             --location \
             --request "${FUNCNAME[2]}" \
             --show-error \
             --silent \
            "$@" "$url"
    )
}


function POST
{
    "$@"
}

function GET
{
    "$@"
}

function body
{
    function json
    {
        jq "${@:-.}" "$body_file"
    }

    function raw
    {
        cat "$body_file"
    }

    "${@:-raw}"
}

function headers
{
    cat "$header_file"
}

function header
{
    headers | grep -Poi "(?<=$1: ).+"
}

function bearer
{
    local bearer_file=/tmp/bearer

    function create
    {
        cat > "$bearer_file"
    }

    function get
    {
        cat "$bearer_file"
    }

    "${@:-get}"
}


function /users/login # JSON_DATA
{
	request --data "$@"
    header Token | bearer create
}

function /users/me
{
    request -H "Authorization: Bearer $(bearer)"
    body json
}

function /posts # JSON_DATA
{
    request -H "Authorization: Bearer $(bearer)" --data "$1"
    body json
}

function /teams/name/:team_name/channels/name/:channel_name
{
    request -H "Authorization: Bearer $(bearer)"
    body json
}

usage.sh

# Get a bearer token using user and password
# https://api.mattermost.com/#tag/authentication
POST /users/login '
{
    "login_id": "j.baratoux",
    "password": "secret"
}'

# Print information about the curent user
GET /users/me

# Get a channel by name and team name
team_name=qwant
channel_name=town-square
GET /teams/name/:team_name/channels/name/:channel_name

# Create a post
# https://api.mattermost.com/#tag/posts%2Fpaths%2F~1posts%2Fpost
POST /posts "
{
    \"channel_id\": \"$(body json -r .id)\",
    \"message\": \"Posted on $(date)\"
}"