/**
 * Redis command syntax diagnostics for the query editor.
 *
 * Mirrors the shape of `sqlSemantic/diagnostics.ts` so the editor's diagnostic
 * pipeline (StateField + Decoration.mark) can render them with no extra wiring.
 * Diagnostics are produced per-line (one Redis command per line — matching the
 * execution contract in `queryStore.executeTabSql`).
 */
import type { SqlTextSpan } from "@/types/database";
import type { SqlSemanticDiagnostic } from "@/lib/sql/semantic/diagnostics";
import { resolveRedisCommandSpec } from "@/lib/redis/redisCommandTable";

export interface RedisArgvToken {
  /** Token text (raw, case preserved). */
  value: string;
  /** 1-based start/end character columns within the source line. */
  startColumn: number;
  endColumn: number;
}

export interface RedisArgvResult {
  argv: RedisArgvToken[];
  /** True when a quoted string was not closed before end-of-line. */
  unclosedQuote: boolean;
  /** Column where an unclosed quote started (1-based), if any. */
  unclosedQuoteStart?: number;
}

/**
 * Tokenize a single Redis command line into argv, mirroring the server-side
 * `parse_command_argv` rules (whitespace separation, single/double quotes,
 * backslash escapes). Trailing `;` is stripped. Each token records its column
 * span so diagnostics can underline the offending token.
 */
export function tokenizeRedisLine(line: string): RedisArgvResult {
  const argv: RedisArgvToken[] = [];
  let i = 0;
  const n = line.length;
  let unclosedQuote = false;
  let unclosedQuoteStart: number | undefined;

  while (i < n) {
    // Skip whitespace.
    while (i < n && (line[i] === " " || line[i] === "\t")) i++;
    if (i >= n) break;

    const startColumn = i + 1; // 1-based
    let value = "";
    let closed = false;
    const ch = line[i];

    if (ch === '"' || ch === "'") {
      if (unclosedQuoteStart === undefined) unclosedQuoteStart = startColumn;
      const quote = ch;
      i++; // consume opening quote
      let escaping = false;
      while (i < n) {
        const c = line[i];
        if (escaping) {
          value += c;
          escaping = false;
          i++;
          continue;
        }
        if (c === "\\") {
          escaping = true;
          i++;
          continue;
        }
        if (c === quote) {
          i++; // consume closing quote
          closed = true;
          break;
        }
        value += c;
        i++;
      }
      if (!closed && i >= n) {
        unclosedQuote = true;
      } else {
        // If the quote was closed, allow trailing chars until whitespace as part
        // of the same token (e.g. `"a"b` → `ab`) to match common tokenizers.
        while (i < n && line[i] !== " " && line[i] !== "\t") {
          value += line[i];
          i++;
        }
      }
    } else {
      closed = true; // unquoted tokens are always complete
      while (i < n && line[i] !== " " && line[i] !== "\t") {
        if (line[i] === "\\") {
          i++;
          if (i < n) {
            value += line[i];
            i++;
          }
          continue;
        }
        value += line[i];
        i++;
      }
    }

    // Strip a single trailing semicolon (line-level `;` terminator).
    if (value.endsWith(";")) value = value.slice(0, -1);

    if (value.length > 0 || !closed) {
      argv.push({ value, startColumn, endColumn: i + 1 });
    }
  }

  return { argv, unclosedQuote, unclosedQuoteStart };
}

function aritySatisfied(arity: number, tokenCount: number): boolean {
  if (arity > 0) return tokenCount === arity;
  if (arity < 0) return tokenCount >= -arity;
  return true; // arity 0 — unspecified, accept anything
}

function describeArity(arity: number): string {
  if (arity > 0) return `exactly ${arity - 1} argument${arity - 1 === 1 ? "" : "s"}`;
  if (arity < 0) return `at least ${-arity - 1} argument${-arity - 1 === 1 ? "" : "s"}`;
  return "any number of arguments";
}

function lineSpan(lineIndex: number, startColumn: number, endColumn: number): SqlTextSpan {
  // SqlTextSpan columns are 1-based and inclusive; map onto the physical line.
  return {
    start_line: lineIndex,
    start_column: startColumn,
    end_line: lineIndex,
    end_column: endColumn,
  };
}

/**
 * Build diagnostics for the whole editor source (multi-line). Each non-empty,
 * non-comment line is parsed as one Redis command.
 */
export function buildRedisSyntaxDiagnostics(source: string): SqlSemanticDiagnostic[] {
  const diagnostics: SqlSemanticDiagnostic[] = [];
  const lines = source.split(/\r?\n/);

  for (let lineIndex = 0; lineIndex < lines.length; lineIndex++) {
    const rawLine = lines[lineIndex];
    const lineNo = lineIndex + 1; // 1-based line number for SqlTextSpan
    if (!rawLine || !rawLine.trim()) continue;
    // Skip comment-ish lines (Redis has no official comments, but `#`/`--` are
    // commonly used by users as notes).
    if (/^\s*(#|--)/.test(rawLine)) continue;

    const { argv, unclosedQuote, unclosedQuoteStart } = tokenizeRedisLine(rawLine);

    if (unclosedQuote) {
      const startCol = unclosedQuoteStart ?? 1;
      diagnostics.push({
        span: lineSpan(lineNo, startCol, Math.max(rawLine.length, startCol)),
        message: "Unclosed quote",
        severity: "error",
      });
      continue; // further checks are unreliable without a clean parse
    }

    if (argv.length === 0) continue;

    const upper = argv.map((token) => token.value.toUpperCase());
    const spec = resolveRedisCommandSpec(upper);
    const commandToken = argv[0];

    if (!spec) {
      diagnostics.push({
        span: lineSpan(lineNo, commandToken.startColumn, commandToken.endColumn),
        message: `Unknown command '${argv[0].value}'`,
        severity: "error",
      });
      continue;
    }

    if (!aritySatisfied(spec.arity, argv.length)) {
      diagnostics.push({
        span: lineSpan(lineNo, commandToken.startColumn, commandToken.endColumn),
        message: `Wrong number of arguments for '${argv[0].value}': expected ${describeArity(spec.arity)}, got ${argv.length - 1}`,
        severity: "error",
      });
      // Don't also emit a safety marker on the same token — arity error is clearer.
      continue;
    }

    if (spec.safety === "blocked") {
      diagnostics.push({
        span: lineSpan(lineNo, commandToken.startColumn, commandToken.endColumn),
        message: `Blocked command '${argv[0].value}'`,
        severity: "error",
      });
    } else if (spec.safety === "confirm") {
      diagnostics.push({
        span: lineSpan(lineNo, commandToken.startColumn, commandToken.endColumn),
        message: `Dangerous command '${argv[0].value}' — confirmation recommended`,
        severity: "warning",
      });
    }
  }

  return diagnostics;
}

/**
 * Gate diagnostics while the user is actively typing the command name on the
 * current line, to avoid transient "Unknown command" noise. Mirrors the intent
 * of `shouldRunSqlSemanticDiagnostics`.
 */
export function shouldRunRedisDiagnostics(source: string, cursor: number): boolean {
  if (!source.trim()) return false;
  // Find the line the cursor is on.
  const upto = source.slice(0, cursor);
  const lineStart = upto.lastIndexOf("\n") + 1;
  const lineText = source.slice(lineStart, cursor);
  const trimmed = lineText.trimStart();
  // If the cursor line only has whitespace and a partial first token with no
  // separating whitespace yet, we're still typing the command name → wait.
  if (trimmed.length > 0 && !/\s/.test(trimmed)) return false;
  return true;
}