export type Position = { offset: number; line: number; column: number }

export type Span = { start: Position; end: Position; file?: string }

export type Program = { type: "Program"; body: Expr | null; span: Span }

export type Expr =
  | Literal
  | Identifier
  | UnaryExpr
  | BinaryExpr
  | LogicalExpr
  | CallExpr
  | MemberExpr
  | IndexExpr
  | ListExpr
  | ErrorExpr

export type LiteralKind = "number" | "string" | "boolean" | "null" | "date" | "duration" | "regex"

export type NumberLiteral = { type: "Literal"; kind: "number"; value: number; span: Span }
export type StringLiteral = { type: "Literal"; kind: "string"; value: string; span: Span }
export type BooleanLiteral = { type: "Literal"; kind: "boolean"; value: boolean; span: Span }
export type NullLiteral = { type: "Literal"; kind: "null"; value: null; span: Span }
export type DateLiteral = { type: "Literal"; kind: "date"; value: string; span: Span }
export type DurationLiteral = { type: "Literal"; kind: "duration"; value: string; span: Span }
export type RegexLiteral = {
  type: "Literal"
  kind: "regex"
  value: string
  flags: string
  span: Span
}

export type Literal =
  | NumberLiteral
  | StringLiteral
  | BooleanLiteral
  | NullLiteral
  | DateLiteral
  | DurationLiteral
  | RegexLiteral

export type Identifier = { type: "Identifier"; name: string; span: Span }

export type UnaryExpr = { type: "UnaryExpr"; operator: "!" | "-"; argument: Expr; span: Span }

export type BinaryExpr = {
  type: "BinaryExpr"
  operator: "+" | "-" | "*" | "/" | "%" | "==" | "!=" | ">" | ">=" | "<" | "<="
  left: Expr
  right: Expr
  span: Span
}

export type LogicalExpr = {
  type: "LogicalExpr"
  operator: "&&" | "||"
  left: Expr
  right: Expr
  span: Span
}

export type CallExpr = { type: "CallExpr"; callee: Expr; args: Expr[]; span: Span }

export type MemberExpr = { type: "MemberExpr"; object: Expr; property: string; span: Span }

export type IndexExpr = { type: "IndexExpr"; object: Expr; index: Expr; span: Span }

export type ListExpr = { type: "ListExpr"; elements: Expr[]; span: Span }

export type ErrorExpr = { type: "ErrorExpr"; message: string; span: Span }

export function spanFrom(start: Span, end: Span): Span {
  return { start: start.start, end: end.end, file: start.file || end.file }
}