import type {
  Schema,
  TupleSchema,
  ArraySchema,
  ReferenceSchema,
  StringLiteralSchema,
  UnionSchema,
} from "./types";
import { ParseError } from "./parser";
import { schemaToTypeString } from "./type-utils";

class ValueParser {
  private input: string;
  private schemaString: string;
  private pos: number = 0;

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

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

  parseValue(schema: Schema): unknown {
    this.skipWhitespace();

    switch (schema.type) {
      case "string":
        return this.parseStringValue();
      case "number":
        return this.parseNumberValue();
      case "int":
        return this.parseIntValue();
      case "float":
        return this.parseFloatValue();
      case "boolean":
        return this.parseBooleanValue();
      case "stringLiteral":
        return this.parseStringLiteralValue(schema);
      case "union":
        return this.parseUnionValue(schema);
      case "tuple":
        return this.parseTupleValue(schema);
      case "array":
        return this.parseArrayValue(schema);
      case "reference":
        // Reference values are parsed as strings (IDs) initially, resolved later
        return this.parseReferenceValue(schema);
      case "reverseReference":
        // Reverse references are derived fields, not stored in CSV cells
        // They resolve to null at parse time; actual resolution happens in the loader
        return null;
      default:
        throw new ParseError(
          `Unknown schema type: ${(schema as { type: string }).type}`,
          this.pos,
          this.schemaString,
          this.input,
        );
    }
  }

  private parseStringValue(): string {
    let result = "";
    while (this.pos < this.input.length) {
      const char = this.peek();

      if (char === "\\") {
        this.consume();
        const nextChar = this.consume();
        if (
          nextChar === ";" ||
          nextChar === "[" ||
          nextChar === "]" ||
          nextChar === "\\"
        ) {
          result += nextChar;
        } else {
          result += "\\" + nextChar;
        }
      } else if (char === ";" || char === "]") {
        break;
      } else {
        result += this.consume();
      }
    }
    return result.trim();
  }

  private parseNumberValue(): number {
    let numStr = "";
    while (this.pos < this.input.length && /[\d.\-+eE]/.test(this.peek())) {
      numStr += this.consume();
    }
    const num = parseFloat(numStr);
    if (isNaN(num)) {
      throw new ParseError(
        "Invalid number",
        this.pos - numStr.length,
        this.schemaString,
        this.input,
      );
    }
    return num;
  }

  private parseIntValue(): number {
    let numStr = "";
    while (this.pos < this.input.length && /[\d.\-+eE]/.test(this.peek())) {
      numStr += this.consume();
    }
    const num = parseFloat(numStr);
    if (isNaN(num)) {
      throw new ParseError(
        "Invalid number",
        this.pos - numStr.length,
        this.schemaString,
        this.input,
      );
    }
    if (!Number.isInteger(num)) {
      throw new ParseError(
        "Expected integer value",
        this.pos - numStr.length,
        this.schemaString,
        this.input,
      );
    }
    return num;
  }

  private parseFloatValue(): number {
    return this.parseNumberValue();
  }

  private parseBooleanValue(): boolean {
    if (this.consumeStr("true")) {
      return true;
    }
    if (this.consumeStr("false")) {
      return false;
    }
    throw new ParseError(
      "Expected true or false",
      this.pos,
      this.schemaString,
      this.input,
    );
  }

  private parseStringLiteralValue(schema: StringLiteralSchema): string {
    const quote = this.peek();

    // 支持带引号或不带引号的字符串值
    if (quote === '"' || quote === "'") {
      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 === ";"
          ) {
            value += nextChar;
          } else {
            value += "\\" + nextChar;
          }
        } else if (char === quote) {
          this.consume(); // Consume closing quote

          if (value !== schema.value) {
            throw new ParseError(
              `Invalid value '"${value}"'. Expected '"${schema.value}"'`,
              this.pos,
              this.schemaString,
              this.input,
            );
          }

          return value;
        } else {
          value += this.consume();
        }
      }

      throw new ParseError(
        "Unterminated string literal",
        this.pos,
        this.schemaString,
        this.input,
      );
    } else {
      // 不带引号的字符串，像普通字符串一样解析
      let value = "";
      while (this.pos < this.input.length) {
        const char = this.peek();
        if (char === ";" || char === "]" || char === ")") {
          break;
        }
        value += this.consume();
      }

      value = value.trim();

      if (value !== schema.value) {
        throw new ParseError(
          `Invalid value '${value}'. Expected '${schema.value}'`,
          this.pos - value.length,
          this.schemaString,
          this.input,
        );
      }

      return value;
    }
  }

  private parseUnionValue(schema: UnionSchema): unknown {
    const savedPos = this.pos;
    const errors: Error[] = [];

    // Try each union member until one succeeds
    for (let i = 0; i < schema.members.length; i++) {
      this.pos = savedPos;
      try {
        return this.parseValue(schema.members[i]);
      } catch (e) {
        errors.push(e as Error);
        // Continue to next member
      }
    }

    // If all members fail, throw a descriptive error
    throw new ParseError(
      `Value does not match any union member. Tried ${schema.members.length} alternatives.`,
      this.pos,
      this.schemaString,
      this.input,
    );
  }

  private parseTupleValue(schema: TupleSchema): unknown[] {
    if (!this.consumeStr("[")) {
      throw new ParseError(
        "Expected [",
        this.pos,
        this.schemaString,
        this.input,
      );
    }

    this.skipWhitespace();

    if (this.peek() === "]") {
      this.consume();
      return [];
    }

    const result: unknown[] = [];
    for (let i = 0; i < schema.elements.length; i++) {
      this.skipWhitespace();
      const elementSchema = schema.elements[i];

      // Try to consume optional name prefix (e.g., "current:")
      if (elementSchema.name) {
        this.skipWhitespace();
        const savedPos = this.pos;
        if (this.consumeStr(`${elementSchema.name}:`)) {
          this.skipWhitespace();
        } else {
          // Name not found, reset position and continue without name
          this.pos = savedPos;
        }
      }

      result.push(this.parseValue(elementSchema.schema));
      this.skipWhitespace();

      if (i < schema.elements.length - 1) {
        if (!this.consumeStr(";")) {
          throw new ParseError(
            "Expected ;",
            this.pos,
            this.schemaString,
            this.input,
          );
        }
      }
    }

    this.skipWhitespace();

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

    return result;
  }

  private parseArrayValue(schema: ArraySchema): unknown[] {
    if (this.pos >= this.input.length || !this.input.trim()) {
      return [];
    }

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

    this.skipWhitespace();

    if (this.peek() === "]") {
      this.consume();
      return [];
    }

    const result: unknown[] = [];
    while (true) {
      this.skipWhitespace();

      result.push(this.parseValue(schema.element));
      this.skipWhitespace();

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

    this.skipWhitespace();

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

    return result;
  }

  private parseReferenceValue(
    schema: ReferenceSchema,
  ): string | string[] | null {
    if (schema.isOptional) {
      this.skipWhitespace();
      if (this.pos >= this.input.length) {
        return null;
      }
    }

    if (schema.isArray) {
      // Parse array of IDs: [id1; id2; id3]
      if (!this.consumeStr("[")) {
        throw new ParseError(
          "Expected [",
          this.pos,
          this.schemaString,
          this.input,
        );
      }

      this.skipWhitespace();

      if (this.peek() === "]") {
        this.consume();
        return [];
      }

      const ids: string[] = [];
      while (true) {
        this.skipWhitespace();
        // Parse each ID as a string
        let id = "";
        while (
          this.pos < this.input.length &&
          this.peek() !== ";" &&
          this.peek() !== "]"
        ) {
          id += this.consume();
        }
        ids.push(id.trim());
        this.skipWhitespace();

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

      this.skipWhitespace();

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

      return ids;
    } else {
      // Parse single ID as string
      let id = "";
      while (this.pos < this.input.length) {
        const char = this.peek();
        if (char === ";" || char === "]" || char === ",") {
          break;
        }
        id += this.consume();
      }
      return id.trim();
    }
  }

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

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

export function parseValue(
  schema: Schema,
  valueString: string,
  schemaString?: string,
): unknown {
  const sStr = schemaString || schemaToTypeString(schema);
  const parser = new ValueParser(valueString.trim(), sStr);
  const value = parser.parseValue(schema);

  if (parser.getPosition() < parser.getInputLength()) {
    throw new ParseError(
      "Unexpected input after value",
      parser.getPosition(),
      sStr,
      valueString.trim(),
    );
  }

  return value;
}