;; copyright (c) 2019 Sean Corfield, all rights reserved

(ns next.jdbc.sql
  "Some utility functions that make common operations easier by
  providing some syntactic sugar over `execute!`/`execute-one!`.

  This is intended to provide a minimal level of parity with
  `clojure.java.jdbc` (`insert!`, `insert-multi!`, `query`, `find-by-keys`,
  `get-by-id`, `update!`, and `delete!`).

  For anything more complex, use a library like HoneySQL
  https://github.com/jkk/honeysql to generate SQL + parameters.

  The following options are supported:
  * `:table-fn` -- specify a function used to convert table names (strings)
      to SQL entity names -- see the `next.jdbc.quoted` namespace for the
      most common quoting strategy functions,
  * `:column-fn` -- specify a function used to convert column names (strings)
      to SQL entity names -- see the `next.jdbc.quoted` namespace for the
      most common quoting strategy functions.

  In addition, `find-by-keys` supports `:order-by` to add an `ORDER BY`
  clause to the generated SQL."
  (:require [clojure.string :as str]
            [next.jdbc :refer [execute! execute-one!]]))

(set! *warn-on-reflection* true)

(defn- by-keys
  "Given a hash map of column names and values and a clause type
  (`:set`, `:where`), return a vector of a SQL clause and its parameters.

  Applies any `:column-fn` supplied in the options."
  [key-map clause opts]
  (let [entity-fn      (:column-fn opts identity)
        [where params] (reduce-kv (fn [[conds params] k v]
                                    (let [e (entity-fn (name k))]
                                      (if (and (= :where clause) (nil? v))
                                        [(conj conds (str e " IS NULL")) params]
                                        [(conj conds (str e " = ?")) (conj params v)])))
                                  [[] []]
                                  key-map)]
    (assert (seq where) "key-map may not be empty")
    (into [(str (str/upper-case (name clause)) " "
                (str/join (if (= :where clause) " AND " ", ") where))]
          params)))

(defn- as-keys
  "Given a hash map of column names and values, return a string of all the
  column names.

  Applies any `:column-fn` supplied in the options."
  [key-map opts]
  (str/join ", " (map (comp (:column-fn opts identity) name) (keys key-map))))

(defn- as-?
  "Given a hash map of column names and values, or a vector of column names,
  return a string of `?` placeholders for them."
  [key-map opts]
  (str/join ", " (repeat (count key-map) "?")))

(defn- for-order-col
  "Given a column name, or a pair of column name and direction,
  return the sub-clause for addition to `ORDER BY`."
  [col opts]
  (let [entity-fn (:column-fn opts identity)]
    (cond (keyword? col)
          (entity-fn (name col))

          (and (vector? col) (= 2 (count col)) (keyword? (first col)))
          (str (entity-fn (name (first col)))
               " "
               (or (get {:asc "ASC" :desc "DESC"} (second col))
                   (throw (IllegalArgumentException.
                           (str ":order-by " col
                                " expected :asc or :desc")))))
          :else
          (throw (IllegalArgumentException.
                  (str ":order-by expected keyword or keyword pair,"
                       " found: " col))))))

(defn- for-order
  "Given an `:order-by` vector, return an `ORDER BY` clause."
  [order-by opts]
  (when-not (vector? order-by)
    (throw (IllegalArgumentException. ":order-by must be a vector")))
  (assert (seq order-by) ":order-by may not be empty")
  (str "ORDER BY "
       (str/join ", " (map #(for-order-col % opts) order-by))))

(defn- for-query
  "Given a table name and either a hash map of column names and values or a
  vector of SQL (where clause) and its parameters, return a vector of the
  full `SELECT` SQL string and its parameters.

  Applies any `:table-fn` / `:column-fn` supplied in the options."
  [table where-params opts]
  (let [entity-fn    (:table-fn opts identity)
        where-params (if (map? where-params)
                       (by-keys where-params :where opts)
                       (into [(str "WHERE " (first where-params))]
                             (rest where-params)))]
    (into [(str "SELECT * FROM " (entity-fn (name table))
                " " (first where-params)
                (when-let [order-by (:order-by opts)]
                  (str " " (for-order order-by opts))))]
          (rest where-params))))

(defn- for-delete
  "Given a table name and either a hash map of column names and values or a
  vector of SQL (where clause) and its parameters, return a vector of the
  full `DELETE` SQL string and its parameters.

  Applies any `:table-fn` / `:column-fn` supplied in the options."
  [table where-params opts]
  (let [entity-fn    (:table-fn opts identity)
        where-params (if (map? where-params)
                       (by-keys where-params :where opts)
                       (into [(str "WHERE " (first where-params))]
                             (rest where-params)))]
    (into [(str "DELETE FROM " (entity-fn (name table))
                " " (first where-params))]
          (rest where-params))))

(defn- for-update
  "Given a table name, a vector of column names to set and their values, and
  either a hash map of column names and values or a vector of SQL (where clause)
  and its parameters, return a vector of the full `UPDATE` SQL string and its
  parameters.

  Applies any `:table-fn` / `:column-fn` supplied in the options."
  [table key-map where-params opts]
  (let [entity-fn    (:table-fn opts identity)
        set-params   (by-keys key-map :set opts)
        where-params (if (map? where-params)
                       (by-keys where-params :where opts)
                       (into [(str "WHERE " (first where-params))]
                             (rest where-params)))]
    (-> [(str "UPDATE " (entity-fn (name table))
              " " (first set-params)
              " " (first where-params))]
        (into (rest set-params))
        (into (rest where-params)))))

(defn- for-insert
  "Given a table name and a hash map of column names and their values,
  return a vector of the full `INSERT` SQL string and its parameters.

  Applies any `:table-fn` / `:column-fn` supplied in the options."
  [table key-map opts]
  (let [entity-fn (:table-fn opts identity)
        params    (as-keys key-map opts)
        places    (as-? key-map opts)]
    (assert (seq key-map) "key-map may not be empty")
    (into [(str "INSERT INTO " (entity-fn (name table))
                " (" params ")"
                " VALUES (" places ")")]
          (vals key-map))))

(defn- for-insert-multi
  "Given a table name, a vector of column names, and a vector of row values
  (each row is a vector of its values), return a vector of the full `INSERT`
  SQL string and its parameters.

  Applies any `:table-fn` / `:column-fn` supplied in the options."
  [table cols rows opts]
  (assert (apply = (count cols) (map count rows))
          "column counts are not consistent across cols and rows")
  ;; to avoid generating bad SQL
  (assert (seq cols) "cols may not be empty")
  (assert (seq rows) "rows may not be empty")
  (let [table-fn  (:table-fn opts identity)
        column-fn (:column-fn opts identity)
        params    (str/join ", " (map (comp column-fn name) cols))
        places    (as-? (first rows) opts)]
    (into [(str "INSERT INTO " (table-fn (name table))
                " (" params ")"
                " VALUES "
                (str/join ", " (repeat (count rows) (str "(" places ")"))))]
          cat
          rows)))

(defn insert!
  "Syntactic sugar over `execute-one!` to make inserting hash maps easier.

  Given a connectable object, a table name, and a data hash map, inserts the
  data as a single row in the database and attempts to return a map of generated
  keys."
  ([connectable table key-map]
   (insert! connectable table key-map {}))
  ([connectable table key-map opts]
   (execute-one! connectable
                 (for-insert table key-map opts)
                 (merge {:return-keys true} opts))))

(defn insert-multi!
  "Syntactic sugar over `execute!` to make inserting columns/rows easier.

  Given a connectable object, a table name, a sequence of column names, and
  a vector of rows of data (vectors of column values), inserts the data as
  multiple rows in the database and attempts to return a vector of maps of
  generated keys.

  Note: this expands to a single SQL statement with placeholders for every
  value being inserted -- for large sets of rows, this may exceed the limits
  on SQL string size and/or number of parameters for your JDBC driver or your
  database!"
  ([connectable table cols rows]
   (insert-multi! connectable table cols rows {}))
  ([connectable table cols rows opts]
   (if (seq rows)
     (execute! connectable
               (for-insert-multi table cols rows opts)
               (merge {:return-keys true} opts))
     [])))

(defn query
  "Syntactic sugar over `execute!` to provide a query alias.

  Given a connectable object, and a vector of SQL and its parameters,
  returns a vector of hash maps of rows that match."
  ([connectable sql-params]
   (query connectable sql-params {}))
  ([connectable sql-params opts]
   (execute! connectable sql-params opts)))

(defn find-by-keys
  "Syntactic sugar over `execute!` to make certain common queries easier.

  Given a connectable object, a table name, and either a hash map of
  columns and values to search on or a vector of a SQL where clause and
  parameters, returns a vector of hash maps of rows that match.

  If the `:order-by` option is present, add an `ORDER BY` clause. `:order-by`
  should be a vector of column names or pairs of column name / direction,
  which can be `:asc` or `:desc`."
  ([connectable table key-map]
   (find-by-keys connectable table key-map {}))
  ([connectable table key-map opts]
   (execute! connectable (for-query table key-map opts) opts)))

(defn get-by-id
  "Syntactic sugar over `execute-one!` to make certain common queries easier.

  Given a connectable object, a table name, and a primary key value, returns
  a hash map of the first row that matches.

  By default, the primary key is assumed to be `id` but that can be overridden
  in the five-argument call."
  ([connectable table pk]
   (get-by-id connectable table pk :id {}))
  ([connectable table pk opts]
   (get-by-id connectable table pk :id opts))
  ([connectable table pk pk-name opts]
   (execute-one! connectable (for-query table {pk-name pk} opts) opts)))

(defn update!
  "Syntactic sugar over `execute-one!` to make certain common updates easier.

  Given a connectable object, a table name, a hash map of columns and values
  to set, and either a hash map of columns and values to search on or a vector
  of a SQL where clause and parameters, perform an update on the table."
  ([connectable table key-map where-params]
   (update! connectable table key-map where-params {}))
  ([connectable table key-map where-params opts]
   (execute-one! connectable
                 (for-update table key-map where-params opts)
                 opts)))

(defn delete!
  "Syntactic sugar over `execute-one!` to make certain common deletes easier.

  Given a connectable object, a table name, and either a hash map of columns
  and values to search on or a vector of a SQL where clause and parameters,
  perform a delete on the table."
  ([connectable table where-params]
   (delete! connectable table where-params {}))
  ([connectable table where-params opts]
   (execute-one! connectable (for-delete table where-params opts) opts)))