feat: web: serve openapi.json

Serving the OpenAPI JSON schema means that clients can auto-discover how
to use the API. I am particularly interested in this because open-webui
can use OpenAPI to add context to LLM responses.

hledger-web/Hledger/Web/Handler/MiscR.hs

@@ -19,10 +19,14 @@ module Hledger.Web.Handler.MiscR
   , getManageR
   , getRobotsR
   , getRootR
+  , getOpenApiR
   ) where
 
 import qualified Data.Map as M
 import qualified Data.Text as T
+import qualified Data.Yaml as Yaml
+import qualified Data.ByteString as BS
+import Data.FileEmbed (embedFile)
 import Yesod.Default.Handlers (getFaviconR, getRobotsR)
 
 import Hledger
@@ -107,3 +111,13 @@ getAccounttransactionsR a = do
       styleAmounts (journalCommodityStylesWith HardRounding j) $
       accountTransactionsReport rspec{_rsQuery=Any} j thisacctq
 
+openApiYaml :: BS.ByteString
+openApiYaml = $(embedFile "config/openapi.yaml")
+
+getOpenApiR :: Handler Value
+getOpenApiR =
+  case Yaml.decodeEither' openApiYaml of
+    Left _ -> notFound
+    Right openapi -> do
+      addHeader "Content-Type" "application/json"
+      return openapi

hledger-web/config/routes

@@ -2,6 +2,8 @@
 /robots.txt      RobotsR         GET
 /static          StaticR         Static getStatic
 
+/openapi.json    OpenApiR        GET
+
 /                RootR           GET
 /journal         JournalR        GET
 /register        RegisterR       GET

hledger-web/hledger-web.cabal

@@ -176,6 +176,7 @@ library
     , data-default
     , directory >=1.2.3.0
     , extra >=1.7.11
+    , file-embed >=0.0.16.0
     , filepath
     , githash >=0.1.6.2
     , hjsmin

hledger-web/package.yaml

@@ -123,6 +123,7 @@ library:
   - Decimal >=0.5.1
   - directory >=1.2.3.0
   - extra >=1.7.11
+  - file-embed >=0.0.16.0
   - filepath
   - githash >=0.1.6.2
   - hjsmin