import { JsonValue } from "@angular-devkit/core"
import { Tree } from "@angular-devkit/schematics"
import {
  Node,
  ParseError,
  applyEdits,
  findNodeAtLocation,
  getNodeValue,
  modify,
  parseTree,
  printParseErrorCode,
} from "jsonc-parser"

export type InsertionIndex = (properties: string[]) => number
export type JSONPath = (string | number)[]

/** @internal */
export class JSONFile {
  content: string

  constructor(private readonly host: Tree, private readonly path: string) {
    this.content = this.host.readText(this.path)
  }

  private _jsonAst: Node | undefined
  private get JsonAst(): Node | undefined {
    if (this._jsonAst) {
      return this._jsonAst
    }

    const errors: ParseError[] = []
    this._jsonAst = parseTree(this.content, errors, {
      allowTrailingComma: true,
    })
    if (errors.length) {
      const { error, offset } = errors[0]
      throw new Error(
        `Failed to parse "${
          this.path
        }" as JSON AST Object. ${printParseErrorCode(
          error
        )} at location: ${offset}.`
      )
    }

    return this._jsonAst
  }

  get(jsonPath: JSONPath): unknown {
    const jsonAstNode = this.JsonAst
    if (!jsonAstNode) {
      return undefined
    }

    if (jsonPath.length === 0) {
      return getNodeValue(jsonAstNode)
    }

    const node = findNodeAtLocation(jsonAstNode, jsonPath)

    return node === undefined ? undefined : getNodeValue(node)
  }

  modify(
    jsonPath: JSONPath,
    value: JsonValue | undefined,
    insertInOrder?: InsertionIndex | false
  ): void {
    let getInsertionIndex: InsertionIndex | undefined
    if (insertInOrder === undefined) {
      const property = jsonPath.slice(-1)[0]
      getInsertionIndex = (properties) =>
        [...properties, property].sort().findIndex((p) => p === property)
    } else if (insertInOrder !== false) {
      getInsertionIndex = insertInOrder
    }

    const edits = modify(this.content, jsonPath, value, {
      getInsertionIndex,
      formattingOptions: {
        insertSpaces: true,
        tabSize: 2,
      },
    })

    this.content = applyEdits(this.content, edits)
    this.host.overwrite(this.path, this.content)
    this._jsonAst = undefined
  }

  remove(jsonPath: JSONPath): void {
    if (this.get(jsonPath) !== undefined) {
      this.modify(jsonPath, undefined)
    }
  }
}