import type {
  Schema,
  PrimitiveSchema,
  TupleSchema,
  ArraySchema,
  NamedSchema,
  ReferenceSchema,
  ReverseReferenceSchema,
  StringLiteralSchema,
  UnionSchema,
} from "./types";

export class ParseError extends Error {
  constructor(
    message: string,
    public position?: number,
    public schema?: string,
    public value?: string,
  ) {
    let fullMessage = message;
    if (position !== undefined) {
      fullMessage += ` at position ${position}`;
    }
    if (schema !== undefined) {
      fullMessage += `. Schema: ${schema}`;
    }
    if (value !== undefined) {
      fullMessage += `. Value: ${value}`;
    }
    super(fullMessage);
    this.name = "ParseError";
  }
}

export interface ReferenceInfo {
  /** Referenced table name (e.g., 'parts' from '@parts[]') */
  tableName: string;
  /** Whether it's an array reference */
  isArray: boolean;
}

class Parser {
  private input: string;
  private pos: number = 0;

  constructor(input: string) {
    this.input = input;
  }

  private peek(): string {
    return this.input[this.pos] || "";
  }

  private consume(): string {
    return this.input[this.pos++] || "";
  }

  private skipWhitespace(): void {
    while (this.pos < this.input.length && /\s/.test(this.input[this.pos])) {
      this.pos++;
    }
  }

  private match(str: string): boolean {
    return this.input.slice(this.pos, this.pos + str.length) === str;
  }

  private consumeStr(str: string): boolean {
    if (this.match(str)) {
      this.pos += str.length;
      return true;
    }
    return false;
  }

  getPosition(): number {
    return this.pos;
  }

  getInputLength(): number {
    return this.input.length;
  }

  parseSchema(): Schema {
    this.skipWhitespace();

    // Parse the first schema element
    let schema = this.parseSchemaInternal();
    this.skipWhitespace();

    // Check for array suffix: type[]
    if (this.consumeStr("[")) {
      this.skipWhitespace();
      if (!this.consumeStr("]")) {
        throw new ParseError("Expected ]", this.pos);
      }
      schema = { type: "array", element: schema };
      this.skipWhitespace();
    }

    // Check for union type (| symbol)
    if (this.consumeStr("|")) {
      const members: Schema[] = [schema];

      while (true) {
        this.skipWhitespace();
        const member = this.parseSchemaInternal();
        members.push(member);
        this.skipWhitespace();

        if (!this.consumeStr("|")) {
          break;
        }
      }

      return {
        type: "union",
        members,
      };
    }

    return schema;
  }

  private parseSchemaInternal(): Schema {
    this.skipWhitespace();

    // Check for parentheses (grouping)
    if (this.consumeStr("(")) {
      this.skipWhitespace();
      const schema = this.parseSchema(); // Recursive call for nested unions
      this.skipWhitespace();

      if (!this.consumeStr(")")) {
        throw new ParseError("Expected )", this.pos);
      }

      // Check if there's an array suffix: (union)[]
      this.skipWhitespace();
      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        return { type: "array", element: schema };
      }

      return schema;
    }

    // Check for string literal syntax: "value" or 'value'
    if (this.peek() === '"' || this.peek() === "'") {
      return this.parseStringLiteralSchema();
    }

    // Check for reverse reference syntax: ~tablename(foreignKey)
    if (this.consumeStr("~")) {
      return this.parseReverseReferenceSchema();
    }

    // Check for reference syntax: @tablename[]
    if (this.consumeStr("@")) {
      return this.parseReferenceSchema();
    }

    if (this.consumeStr("string")) {
      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        return { type: "array", element: { type: "string" } };
      }
      return { type: "string" };
    }

    if (this.consumeStr("number")) {
      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        return { type: "array", element: { type: "number" } };
      }
      return { type: "number" };
    }

    if (this.consumeStr("int")) {
      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        return { type: "array", element: { type: "int" } };
      }
      return { type: "int" };
    }

    if (this.consumeStr("float")) {
      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        return { type: "array", element: { type: "float" } };
      }
      return { type: "float" };
    }

    if (this.consumeStr("boolean")) {
      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        return { type: "array", element: { type: "boolean" } };
      }
      return { type: "boolean" };
    }

    if (this.consumeStr("[")) {
      const elements: NamedSchema[] = [];
      this.skipWhitespace();

      if (this.peek() === "]") {
        this.consume();
        throw new ParseError("Empty array/tuple not allowed", this.pos);
      }

      elements.push(this.parseNamedSchema());
      this.skipWhitespace();

      if (this.consumeStr(";")) {
        const remainingElements: NamedSchema[] = [];
        while (true) {
          this.skipWhitespace();
          remainingElements.push(this.parseNamedSchema());
          this.skipWhitespace();

          if (!this.consumeStr(";")) {
            break;
          }
        }
        elements.push(...remainingElements);
      }

      this.skipWhitespace();

      if (!this.consumeStr("]")) {
        throw new ParseError("Expected ]", this.pos);
      }

      if (this.consumeStr("[")) {
        this.skipWhitespace();
        if (!this.consumeStr("]")) {
          throw new ParseError("Expected ]", this.pos);
        }
        if (elements.length === 1 && !elements[0].name) {
          return { type: "array", element: elements[0].schema };
        }
        return { type: "array", element: { type: "tuple", elements } };
      }

      if (elements.length === 1 && !elements[0].name) {
        return { type: "array", element: elements[0].schema };
      }
      return { type: "tuple", elements };
    }

    throw new ParseError(
      `Unknown type: ${this.peek() || "end of input"}`,
      this.pos,
    );
  }

  private parseStringLiteralSchema(): Schema {
    const value = this.parseStringLiteral();
    return {
      type: "stringLiteral",
      value,
    };
  }

  private parseStringLiteral(): string {
    const quote = this.peek();
    if (quote !== '"' && quote !== "'") {
      throw new ParseError("Expected string literal with quotes", this.pos);
    }
    this.consume(); // Consume opening quote

    let value = "";
    while (this.pos < this.input.length) {
      const char = this.peek();

      if (char === "\\") {
        this.consume();
        const nextChar = this.consume();
        if (
          nextChar === '"' ||
          nextChar === "'" ||
          nextChar === "\\" ||
          nextChar === "|" ||
          nextChar === ";" ||
          nextChar === "(" ||
          nextChar === ")"
        ) {
          value += nextChar;
        } else {
          value += "\\" + nextChar;
        }
      } else if (char === quote) {
        this.consume(); // Consume closing quote
        return value;
      } else {
        value += this.consume();
      }
    }

    throw new ParseError("Unterminated string literal", this.pos);
  }

  private parseNamedSchema(): NamedSchema {
    this.skipWhitespace();

    const startpos = this.pos;
    let identifier = "";

    while (this.pos < this.input.length && /[a-zA-Z0-9\-_]/.test(this.peek())) {
      identifier += this.consume();
    }

    if (identifier.length === 0) {
      const schema = this.parseSchema();
      return { schema };
    }

    this.skipWhitespace();

    if (this.consumeStr(":")) {
      this.skipWhitespace();
      const name = identifier;
      const schema = this.parseSchema();
      return { name, schema };
    } else {
      this.pos = startpos;
      const schema = this.parseSchema();
      return { schema };
    }
  }

  private parseReferenceSchema(): Schema {
    // Parse table name
    let tableName = "";
    while (this.pos < this.input.length && /[a-zA-Z0-9\-_]/.test(this.peek())) {
      tableName += this.consume();
    }

    if (tableName.length === 0) {
      throw new ParseError("Expected table name after @", this.pos);
    }

    this.skipWhitespace();

    // Check for array syntax
    if (this.consumeStr("[]")) {
      this.skipWhitespace();
      const isOptional = this.consumeStr("?");
      return {
        type: "reference",
        tableName,
        isArray: true,
        isOptional,
      };
    }

    // Check for optional suffix
    const isOptional = this.consumeStr("?");

    // Single reference (non-array)
    return {
      type: "reference",
      tableName,
      isArray: false,
      isOptional,
    };
  }

  private parseReverseReferenceSchema(): Schema {
    // Parse table name
    let tableName = "";
    while (this.pos < this.input.length && /[a-zA-Z0-9\-_]/.test(this.peek())) {
      tableName += this.consume();
    }

    if (tableName.length === 0) {
      throw new ParseError("Expected table name after ~", this.pos);
    }

    this.skipWhitespace();

    // Parse (foreignKey)
    if (!this.consumeStr("(")) {
      throw new ParseError(
        "Expected ( after reverse reference table name",
        this.pos,
      );
    }

    this.skipWhitespace();

    let foreignKey = "";
    while (this.pos < this.input.length && /[a-zA-Z0-9\-_]/.test(this.peek())) {
      foreignKey += this.consume();
    }

    if (foreignKey.length === 0) {
      throw new ParseError("Expected foreign key name inside ()", this.pos);
    }

    this.skipWhitespace();

    if (!this.consumeStr(")")) {
      throw new ParseError("Expected ) after foreign key name", this.pos);
    }

    this.skipWhitespace();

    // Check for optional suffix
    const isOptional = this.consumeStr("?");

    return {
      type: "reverseReference",
      tableName,
      foreignKey,
      isOptional,
    };
  }
}

export function parseSchema(schemaString: string): Schema {
  const parser = new Parser(schemaString.trim());
  const schema = parser.parseSchema();

  if (parser.getPosition() < parser.getInputLength()) {
    throw new ParseError("Unexpected input after schema", parser.getPosition());
  }

  return schema;
}