// Credits to @bnjmnt4n (https://www.npmjs.com/package/postgrest-query)

import { GenericSchema, Prettify } from "./types";

type Whitespace = " " | "\n" | "\t";

type LowerAlphabet =
	| "a"
	| "b"
	| "c"
	| "d"
	| "e"
	| "f"
	| "g"
	| "h"
	| "i"
	| "j"
	| "k"
	| "l"
	| "m"
	| "n"
	| "o"
	| "p"
	| "q"
	| "r"
	| "s"
	| "t"
	| "u"
	| "v"
	| "w"
	| "x"
	| "y"
	| "z";

type Alphabet = LowerAlphabet | Uppercase<LowerAlphabet>;

type Digit = "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "0";

type Letter = Alphabet | Digit | "_";

type Json = string | number | boolean | null | { [key: string]: Json } | Json[];

// /**
//  * Parsed node types.
//  * Currently only `*` and all other fields.
//  */
// type ParsedNode =
//   | { star: true }
//   | { name: string; original: string }
//   | { name: string; foreignTable: true }
//   | { name: string; type: T };

/**
 * Parser errors.
 */
type ParserError<Message extends string> = { error: true } & Message;
type GenericStringError = ParserError<"Received a generic string">;

/**
 * Trims whitespace from the left of the input.
 */
type EatWhitespace<Input extends string> = string extends Input
	? GenericStringError
	: Input extends `${Whitespace}${infer Remainder}`
	? EatWhitespace<Remainder>
	: Input;

/**
 * Constructs a type definition for a single field of an object.
 *
 * @param Definitions Record of definitions, possibly generated from PostgREST's OpenAPI spec.
 * @param Name Name of the table being queried.
 * @param Field Single field parsed by `ParseQuery`.
 */
type ConstructFieldDefinition<
	Schema extends GenericSchema,
	Row extends Record<string, unknown>,
	Field,
> = Field extends {
	star: true;
}
	? Row
	: Field extends { name: string; original: string; children: unknown[] }
	? {
			[_ in Field["name"]]: GetResultHelper<
				Schema,
				(Schema["Tables"] & Schema["Views"])[Field["original"]]["Row"],
				Field["children"],
				unknown
			> extends infer Child
				? Child | Child[] | null
				: never;
	  }
	: Field extends { name: string; original: string }
	? { [K in Field["name"]]: Row[Field["original"]] }
	: Field extends { name: string; type: infer T }
	? { [K in Field["name"]]: T }
	: Record<string, unknown>;

/**
 * Notes: all `Parse*` types assume that their input strings have their whitespace
 * removed. They return tuples of ["Return Value", "Remainder of text"] or
 * a `ParserError`.
 */

/**
 * Reads a consecutive sequence of more than 1 letter,
 * where letters are `[0-9a-zA-Z_]`.
 */
type ReadLetters<Input extends string> = string extends Input
	? GenericStringError
	: ReadLettersHelper<Input, ""> extends [
			`${infer Letters}`,
			`${infer Remainder}`,
	  ]
	? Letters extends ""
		? ParserError<`Expected letter at \`${Input}\``>
		: [Letters, Remainder]
	: ReadLettersHelper<Input, "">;

type ReadLettersHelper<
	Input extends string,
	Acc extends string,
> = string extends Input
	? GenericStringError
	: Input extends `${infer L}${infer Remainder}`
	? L extends Letter
		? ReadLettersHelper<Remainder, `${Acc}${L}`>
		: [Acc, Input]
	: [Acc, ""];

/**
 * Reads a consecutive sequence of more than 1 double-quoted letters,
 * where letters are `[^"]`.
 */
type ReadQuotedLetters<Input extends string> = string extends Input
	? GenericStringError
	: Input extends `"${infer Remainder}`
	? ReadQuotedLettersHelper<Remainder, ""> extends [
			`${infer Letters}`,
			`${infer Remainder}`,
	  ]
		? Letters extends ""
			? ParserError<`Expected string at \`${Remainder}\``>
			: [Letters, Remainder]
		: ReadQuotedLettersHelper<Remainder, "">
	: ParserError<`Not a double-quoted string at \`${Input}\``>;

type ReadQuotedLettersHelper<
	Input extends string,
	Acc extends string,
> = string extends Input
	? GenericStringError
	: Input extends `${infer L}${infer Remainder}`
	? L extends '"'
		? [Acc, Remainder]
		: ReadQuotedLettersHelper<Remainder, `${Acc}${L}`>
	: ParserError<`Missing closing double-quote in \`"${Acc}${Input}\``>;

/**
 * Parses a (possibly double-quoted) identifier.
 * For now, identifiers are just sequences of more than 1 letter.
 */
type ParseIdentifier<Input extends string> = ReadLetters<Input> extends [
	infer Name,
	`${infer Remainder}`,
]
	? [Name, `${Remainder}`]
	: ReadQuotedLetters<Input> extends [infer Name, `${infer Remainder}`]
	? [Name, `${Remainder}`]
	: ParserError<`No (possibly double-quoted) identifier at \`${Input}\``>;

/**
 * Parses a node.
 * A node is one of the following:
 * - `*`
 * - `field`
 * - `field->json...`
 * - `field(nodes)`
 * - `field!hint(nodes)`
 * - `field!inner(nodes)`
 * - `field!hint!inner(nodes)`
 * - `renamed_field:field`
 * - `renamed_field:field->json...`
 * - `renamed_field:field(nodes)`
 * - `renamed_field:field!hint(nodes)`
 * - `renamed_field:field!inner(nodes)`
 * - `renamed_field:field!hint!inner(nodes)`
 *
 * TODO: casting operators `::text`, more support for JSON operators `->`, `->>`.
 */
type ParseNode<Input extends string> = Input extends ""
	? ParserError<"Empty string">
	: // `*`
	Input extends `*${infer Remainder}`
	? [{ star: true }, EatWhitespace<Remainder>]
	: ParseIdentifier<Input> extends [infer Name, `${infer Remainder}`]
	? EatWhitespace<Remainder> extends `!inner${infer Remainder}`
		? ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
				infer Fields,
				`${infer Remainder}`,
		  ]
			? // `field!inner(nodes)`
			  [
					{ name: Name; original: Name; children: Fields },
					EatWhitespace<Remainder>,
			  ]
			: ParseEmbeddedResource<
					EatWhitespace<Remainder>
			  > extends ParserError<string>
			? ParseEmbeddedResource<EatWhitespace<Remainder>>
			: ParserError<"Expected embedded resource after `!inner`">
		: EatWhitespace<Remainder> extends `!${infer Remainder}`
		? ParseIdentifier<EatWhitespace<Remainder>> extends [
				infer _Hint,
				`${infer Remainder}`,
		  ]
			? EatWhitespace<Remainder> extends `!inner${infer Remainder}`
				? ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
						infer Fields,
						`${infer Remainder}`,
				  ]
					? // `field!hint!inner(nodes)`
					  [
							{ name: Name; original: Name; children: Fields },
							EatWhitespace<Remainder>,
					  ]
					: ParseEmbeddedResource<
							EatWhitespace<Remainder>
					  > extends ParserError<string>
					? ParseEmbeddedResource<EatWhitespace<Remainder>>
					: ParserError<"Expected embedded resource after `!inner`">
				: ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
						infer Fields,
						`${infer Remainder}`,
				  ]
				? // `field!hint(nodes)`
				  [
						{ name: Name; original: Name; children: Fields },
						EatWhitespace<Remainder>,
				  ]
				: ParseEmbeddedResource<
						EatWhitespace<Remainder>
				  > extends ParserError<string>
				? ParseEmbeddedResource<EatWhitespace<Remainder>>
				: ParserError<"Expected embedded resource after `!hint`">
			: ParserError<"Expected identifier after `!`">
		: EatWhitespace<Remainder> extends `:${infer Remainder}`
		? ParseIdentifier<EatWhitespace<Remainder>> extends [
				infer OriginalName,
				`${infer Remainder}`,
		  ]
			? EatWhitespace<Remainder> extends `!inner${infer Remainder}`
				? ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
						infer Fields,
						`${infer Remainder}`,
				  ]
					? // `renamed_field:field!inner(nodes)`
					  [
							{ name: Name; original: OriginalName; children: Fields },
							EatWhitespace<Remainder>,
					  ]
					: ParseEmbeddedResource<
							EatWhitespace<Remainder>
					  > extends ParserError<string>
					? ParseEmbeddedResource<EatWhitespace<Remainder>>
					: ParserError<"Expected embedded resource after `!inner`">
				: EatWhitespace<Remainder> extends `!${infer Remainder}`
				? ParseIdentifier<EatWhitespace<Remainder>> extends [
						infer _Hint,
						`${infer Remainder}`,
				  ]
					? EatWhitespace<Remainder> extends `!inner${infer Remainder}`
						? ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
								infer Fields,
								`${infer Remainder}`,
						  ]
							? // `renamed_field:field!hint!inner(nodes)`
							  [
									{ name: Name; original: OriginalName; children: Fields },
									EatWhitespace<Remainder>,
							  ]
							: ParseEmbeddedResource<
									EatWhitespace<Remainder>
							  > extends ParserError<string>
							? ParseEmbeddedResource<EatWhitespace<Remainder>>
							: ParserError<"Expected embedded resource after `!inner`">
						: ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
								infer Fields,
								`${infer Remainder}`,
						  ]
						? // `renamed_field:field!hint(nodes)`
						  [
								{
									name: Name;
									original: OriginalName;
									children: Fields;
								},
								EatWhitespace<Remainder>,
						  ]
						: ParseEmbeddedResource<
								EatWhitespace<Remainder>
						  > extends ParserError<string>
						? ParseEmbeddedResource<EatWhitespace<Remainder>>
						: ParserError<"Expected embedded resource after `!hint`">
					: ParserError<"Expected identifier after `!`">
				: ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
						infer Fields,
						`${infer Remainder}`,
				  ]
				? // `renamed_field:field(nodes)`
				  [
						{ name: Name; original: OriginalName; children: Fields },
						EatWhitespace<Remainder>,
				  ]
				: ParseJsonAccessor<EatWhitespace<Remainder>> extends [
						infer _PropertyName,
						infer PropertyType,
						`${infer Remainder}`,
				  ]
				? // `renamed_field:field->json...`
				  [{ name: Name; type: PropertyType }, EatWhitespace<Remainder>]
				: ParseEmbeddedResource<
						EatWhitespace<Remainder>
				  > extends ParserError<string>
				? ParseEmbeddedResource<EatWhitespace<Remainder>>
				: // `renamed_field:field`
				  [{ name: Name; original: OriginalName }, EatWhitespace<Remainder>]
			: ParseIdentifier<EatWhitespace<Remainder>>
		: ParseEmbeddedResource<EatWhitespace<Remainder>> extends [
				infer Fields,
				`${infer Remainder}`,
		  ]
		? // `field(nodes)`
		  [
				{ name: Name; original: Name; children: Fields },
				EatWhitespace<Remainder>,
		  ]
		: ParseJsonAccessor<EatWhitespace<Remainder>> extends [
				infer PropertyName,
				infer PropertyType,
				`${infer Remainder}`,
		  ]
		? // `field->json...`
		  [{ name: PropertyName; type: PropertyType }, EatWhitespace<Remainder>]
		: ParseEmbeddedResource<
				EatWhitespace<Remainder>
		  > extends ParserError<string>
		? ParseEmbeddedResource<EatWhitespace<Remainder>>
		: // `field`
		  [{ name: Name; original: Name }, EatWhitespace<Remainder>]
	: ParserError<`Expected identifier at \`${Input}\``>;

/**
 * Parses a JSON property accessor of the shape `->a->b->c`. The last accessor in
 * the series may convert to text by using the ->> operator instead of ->.
 *
 * Returns a tuple of ["Last property name", "Last property type", "Remainder of text"]
 * or the original string input indicating that no opening `->` was found.
 */
type ParseJsonAccessor<Input extends string> =
	Input extends `->${infer Remainder}`
		? Remainder extends `>${infer Remainder}`
			? ParseIdentifier<Remainder> extends [infer Name, `${infer Remainder}`]
				? [Name, string, EatWhitespace<Remainder>]
				: ParserError<"Expected property name after `->>`">
			: ParseIdentifier<Remainder> extends [infer Name, `${infer Remainder}`]
			? ParseJsonAccessor<Remainder> extends [
					infer PropertyName,
					infer PropertyType,
					`${infer Remainder}`,
			  ]
				? [PropertyName, PropertyType, EatWhitespace<Remainder>]
				: [Name, Json, EatWhitespace<Remainder>]
			: ParserError<"Expected property name after `->`">
		: Input;

/**
 * Parses an embedded resource, which is an opening `(`, followed by a sequence of
 * nodes, separated by `,`, then a closing `)`.
 *
 * Returns a tuple of ["Parsed fields", "Remainder of text"], an error,
 * or the original string input indicating that no opening `(` was found.
 */
type ParseEmbeddedResource<Input extends string> =
	Input extends `(${infer Remainder}`
		? ParseNodes<EatWhitespace<Remainder>> extends [
				infer Fields,
				`${infer Remainder}`,
		  ]
			? EatWhitespace<Remainder> extends `)${infer Remainder}`
				? Fields extends []
					? ParserError<"Expected fields after `(`">
					: [Fields, EatWhitespace<Remainder>]
				: ParserError<`Expected ")"`>
			: ParseNodes<EatWhitespace<Remainder>>
		: Input;

/**
 * Parses a sequence of nodes, separated by `,`.
 *
 * Returns a tuple of ["Parsed fields", "Remainder of text"] or an error.
 */
type ParseNodes<Input extends string> = string extends Input
	? GenericStringError
	: ParseNodesHelper<Input, []>;

type ParseNodesHelper<
	Input extends string,
	Fields extends unknown[],
> = ParseNode<Input> extends [infer Field, `${infer Remainder}`]
	? EatWhitespace<Remainder> extends `,${infer Remainder}`
		? ParseNodesHelper<EatWhitespace<Remainder>, [Field, ...Fields]>
		: [[Field, ...Fields], EatWhitespace<Remainder>]
	: ParseNode<Input>;

/**
 * Parses a query.
 * A query is a sequence of nodes, separated by `,`, ensuring that there is
 * no remaining input after all nodes have been parsed.
 *
 * Returns an array of parsed nodes, or an error.
 */
type ParseQuery<Query extends string> = string extends Query
	? GenericStringError
	: ParseNodes<EatWhitespace<Query>> extends [
			infer Fields,
			`${infer Remainder}`,
	  ]
	? EatWhitespace<Remainder> extends ""
		? Fields
		: ParserError<`Unexpected input: ${Remainder}`>
	: ParseNodes<EatWhitespace<Query>>;

type GetResultHelper<
	Schema extends GenericSchema,
	Row extends Record<string, unknown>,
	Fields extends unknown[],
	Acc,
> = Fields extends [infer R]
	? GetResultHelper<
			Schema,
			Row,
			[],
			ConstructFieldDefinition<Schema, Row, R> & Acc
	  >
	: Fields extends [infer R, ...infer Rest]
	? GetResultHelper<
			Schema,
			Row,
			Rest,
			ConstructFieldDefinition<Schema, Row, R> & Acc
	  >
	: Prettify<Acc>;

/**
 * Constructs a type definition for an object based on a given PostgREST query.
 *
 * @param Row Record<string, unknown>.
 * @param Query Select query string literal to parse.
 */
export type GetResult<
	Schema extends GenericSchema,
	Row extends Record<string, unknown>,
	Query extends string,
> = ParseQuery<Query> extends unknown[]
	? GetResultHelper<Schema, Row, ParseQuery<Query>, unknown>
	: ParseQuery<Query>;