// index.cm — Core semantic indexing module.
// Walks AST output from parse (+ optional fold) to build a semantic index.
//
// Two entry points:
//   index_file(src, filename, tokenize_mod, parse_mod, fold_mod) — full pipeline
//   index_ast(ast, tokens, filename) — index a pre-parsed AST

var make_span = function(node) {
  return {
    from_row: node.from_row,
    from_col: node.from_column,
    to_row: node.to_row,
    to_col: node.to_column
  }
}

// Index an already-parsed AST. Tokens are optional (used for doc comments).
var index_ast = function(ast, tokens, filename) {
  var is_actor = ends_with(filename, ".ce")
  var imports = []
  var symbols = []
  var references = []
  var call_sites = []
  var exports_list = []
  var node_counter = 0
  var fn_map = {}
  var _i = 0
  var _j = 0
  var fn = null
  var sym_id = null
  var params_list = null
  var scope = null
  var keys = null
  var key = null
  var entry = null
  var reverse = {}

  // Build function_nr -> {name, outer, from_row} map from ast.functions.
  if (ast.functions != null) {
    _i = 0
    while (_i < length(ast.functions)) {
      fn = ast.functions[_i]
      fn_map[text(fn.function_nr)] = {
        name: fn.name,
        outer: fn.outer,
        from_row: fn.from_row
      }
      _i = _i + 1
    }
  }

  // Walk scope chain upward by `lvl` levels from func_nr.
  var resolve_scope_nr = function(func_nr, lvl) {
    var current = func_nr
    var remaining = lvl
    var info = null
    if (remaining == null || remaining < 0) return null
    while (remaining > 0 && current != null) {
      info = fn_map[text(current)]
      if (info != null) {
        current = info.outer
      } else {
        return null
      }
      remaining = remaining - 1
    }
    return current
  }

  // Resolve a name node to its symbol_id using scope chain.
  var resolve_symbol_id = function(name_node) {
    var decl_fn_nr = resolve_scope_nr(name_node.function_nr, name_node.level)
    var _si = 0
    var s = null
    var e = null
    var kind_str = null
    if (decl_fn_nr == null) return null
    if (ast.scopes == null) return null
    _si = 0
    while (_si < length(ast.scopes)) {
      s = ast.scopes[_si]
      if (s.function_nr == decl_fn_nr) {
        e = s[name_node.name]
        if (e != null) {
          kind_str = e.make
          if (kind_str == "function") kind_str = "fn"
          if (kind_str == "input") kind_str = "param"
          return filename + ":" + name_node.name + ":" + kind_str
        }
      }
      _si = _si + 1
    }
    return null
  }

  // Get enclosing symbol id for a function_nr.
  var get_enclosing = function(func_nr) {
    var info = fn_map[text(func_nr)]
    if (info == null || func_nr == 0) return null
    if (info.name != null) return filename + ":" + info.name + ":fn"
    return null
  }

  // Find doc comment in tokens immediately before target_row.
  var find_doc_comment = function(target_row) {
    var _ti = 0
    var tok = null
    var lines = []
    var line_nr = null
    if (tokens == null) return null
    _ti = 0
    while (_ti < length(tokens)) {
      tok = tokens[_ti]
      if (tok.kind == "comment" && tok.from_row >= target_row - 10 && tok.from_row < target_row) {
        lines[] = tok.value
      }
      if (tok.from_row >= target_row) break
      _ti = _ti + 1
    }
    if (length(lines) > 0) return text(lines, "\n")
    return null
  }

  // Allocate a monotonic node id.
  var next_id = function() {
    node_counter = node_counter + 1
    return node_counter
  }

  // Forward declarations for mutual recursion.
  var walk_expr = null
  var walk_stmts = null
  var walk_stmt = null

  // Walk an expression node, collecting references and call sites.
  walk_expr = function(node, enclosing, is_lhs) {
    var nid = 0
    var ref_kind = null
    var callee_name = null
    var callee_sym = null
    var arg_count = 0
    var _ai = 0
    var enc = null
    var param_name = null

    if (node == null) return

    nid = next_id()

    // Name reference — has function_nr when it's a true variable reference.
    if (node.kind == "name" && node.name != null && node.function_nr != null) {
      if (node.intrinsic != true) {
        ref_kind = is_lhs ? "write" : "read"
        references[] = {
          node_id: nid,
          name: node.name,
          symbol_id: resolve_symbol_id(node),
          span: make_span(node),
          enclosing: enclosing,
          ref_kind: ref_kind
        }
      }
    }

    // Call expression.
    if (node.kind == "(") {
      callee_name = null
      callee_sym = null
      arg_count = (node.list != null) ? length(node.list) : 0

      if (node.expression != null) {
        if (node.expression.kind == "name") {
          callee_name = node.expression.name
          if (node.expression.intrinsic != true && node.expression.function_nr != null) {
            callee_sym = resolve_symbol_id(node.expression)
          }
        } else if (node.expression.kind == ".") {
          if (node.expression.left != null && node.expression.left.kind == "name") {
            callee_name = node.expression.left.name
          }
          if (node.expression.right != null && node.expression.right.name != null) {
            callee_name = (callee_name != null ? callee_name + "." : "") + node.expression.right.name
          }
        }
      }

      if (callee_name != "use") {
        call_sites[] = {
          node_id: nid,
          callee: callee_name,
          callee_symbol_id: callee_sym,
          span: make_span(node),
          enclosing: enclosing,
          args_count: arg_count
        }
      }

      // Also record the callee name as a "call" reference.
      if (node.expression != null && node.expression.kind == "name" &&
          node.expression.function_nr != null && node.expression.intrinsic != true) {
        references[] = {
          node_id: nid,
          name: node.expression.name,
          symbol_id: resolve_symbol_id(node.expression),
          span: make_span(node.expression),
          enclosing: enclosing,
          ref_kind: "call"
        }
      }

      // Walk callee expression (skip name — already recorded above).
      if (node.expression != null && node.expression.kind != "name") {
        walk_expr(node.expression, enclosing, false)
      }

      // Walk arguments.
      if (node.list != null) {
        _ai = 0
        while (_ai < length(node.list)) {
          walk_expr(node.list[_ai], enclosing, false)
          _ai = _ai + 1
        }
      }
      return
    }

    // Function / arrow function expression — walk body.
    if (node.kind == "function" || node.kind == "arrow function") {
      enc = enclosing
      if (node.name != null && node.function_nr != null) {
        enc = filename + ":" + node.name + ":fn"
      }
      // Record params as symbols.
      if (node.list != null) {
        _ai = 0
        while (_ai < length(node.list)) {
          param_name = node.list[_ai].name
          if (param_name != null) {
            symbols[] = {
              symbol_id: filename + ":" + param_name + ":param",
              name: param_name,
              kind: "param",
              decl_span: make_span(node.list[_ai]),
              doc_comment: null,
              scope_fn_nr: node.function_nr,
              params: null
            }
          }
          _ai = _ai + 1
        }
      }
      walk_stmts(node.statements, enc)
      walk_stmts(node.disruption, enc)
      return
    }

    // Assignment operators — left side is a write.
    if (node.kind == "=" || node.kind == "+=" || node.kind == "-=" ||
        node.kind == "*=" || node.kind == "/=" || node.kind == "%=") {
      walk_expr(node.left, enclosing, true)
      walk_expr(node.right, enclosing, false)
      return
    }

    // Property access — only walk left (right is property name, not a ref).
    if (node.kind == ".") {
      walk_expr(node.left, enclosing, false)
      return
    }

    // Index access.
    if (node.kind == "[") {
      walk_expr(node.left, enclosing, false)
      walk_expr(node.right, enclosing, false)
      return
    }

    // Array literal.
    if (node.kind == "array" && node.list != null) {
      _ai = 0
      while (_ai < length(node.list)) {
        walk_expr(node.list[_ai], enclosing, false)
        _ai = _ai + 1
      }
      return
    }

    // Record literal — only walk values, not keys.
    if (node.kind == "record" && node.list != null) {
      _ai = 0
      while (_ai < length(node.list)) {
        if (node.list[_ai] != null) {
          walk_expr(node.list[_ai].right, enclosing, false)
        }
        _ai = _ai + 1
      }
      return
    }

    // Template literal.
    if (node.kind == "template" && node.list != null) {
      _ai = 0
      while (_ai < length(node.list)) {
        walk_expr(node.list[_ai], enclosing, false)
        _ai = _ai + 1
      }
      return
    }

    // Prefix/postfix increment/decrement — treat as write.
    if (node.kind == "++" || node.kind == "--") {
      walk_expr(node.expression, enclosing, true)
      return
    }

    // Ternary.
    if (node.kind == "?" || node.kind == "then") {
      walk_expr(node.expression, enclosing, false)
      walk_expr(node.then, enclosing, false)
      walk_expr(node.else, enclosing, false)
      return
    }

    // Generic fallthrough: walk left, right, expression.
    if (node.left != null) walk_expr(node.left, enclosing, is_lhs)
    if (node.right != null) walk_expr(node.right, enclosing, false)
    if (node.expression != null) walk_expr(node.expression, enclosing, false)
  }

  // Walk an array of statements.
  walk_stmts = function(stmts, enclosing) {
    var _wi = 0
    if (stmts == null) return
    _wi = 0
    while (_wi < length(stmts)) {
      walk_stmt(stmts[_wi], enclosing)
      _wi = _wi + 1
    }
  }

  // Walk a single statement.
  walk_stmt = function(stmt, enclosing) {
    var sym_kind = null
    var s_id = null
    var p_list = null
    var _di = 0
    var local_name = null

    if (stmt == null) return

    // Variable/constant declaration.
    if (stmt.kind == "var" || stmt.kind == "def") {
      if (stmt.left != null && stmt.left.name != null) {
        sym_kind = stmt.kind
        p_list = null

        // Check if RHS is a function expression.
        if (stmt.right != null && (stmt.right.kind == "function" || stmt.right.kind == "arrow function")) {
          sym_kind = "fn"
          p_list = []
          if (stmt.right.list != null) {
            _di = 0
            while (_di < length(stmt.right.list)) {
              if (stmt.right.list[_di].name != null) {
                p_list[] = stmt.right.list[_di].name
              }
              _di = _di + 1
            }
          }
        }

        s_id = filename + ":" + stmt.left.name + ":" + sym_kind
        symbols[] = {
          symbol_id: s_id,
          name: stmt.left.name,
          kind: sym_kind,
          decl_span: make_span(stmt),
          doc_comment: find_doc_comment(stmt.from_row),
          scope_fn_nr: 0,
          params: p_list
        }

        // Check for import: var x = use('path').
        if (stmt.right != null && stmt.right.kind == "(" &&
            stmt.right.expression != null && stmt.right.expression.name == "use" &&
            stmt.right.list != null && length(stmt.right.list) > 0 &&
            stmt.right.list[0].kind == "text") {
          imports[] = {
            local_name: stmt.left.name,
            module_path: stmt.right.list[0].value,
            span: make_span(stmt)
          }
        }
      }

      walk_expr(stmt.right, enclosing, false)
      return
    }

    // Multiple declarations (var_list).
    if (stmt.kind == "var_list" && stmt.list != null) {
      _di = 0
      while (_di < length(stmt.list)) {
        walk_stmt(stmt.list[_di], enclosing)
        _di = _di + 1
      }
      return
    }

    // Expression statement.
    if (stmt.kind == "call") {
      // Check for bare use() as expression statement.
      if (stmt.expression != null && stmt.expression.kind == "(" &&
          stmt.expression.expression != null && stmt.expression.expression.name == "use" &&
          stmt.expression.list != null && length(stmt.expression.list) > 0 &&
          stmt.expression.list[0].kind == "text") {
        imports[] = {
          local_name: null,
          module_path: stmt.expression.list[0].value,
          span: make_span(stmt)
        }
      }
      walk_expr(stmt.expression, enclosing, false)
      return
    }

    // If statement.
    if (stmt.kind == "if") {
      walk_expr(stmt.expression, enclosing, false)
      walk_stmts(stmt.then, enclosing)
      if (stmt.else != null) {
        walk_stmts(stmt.else, enclosing)
      }
      // else-if chain.
      if (stmt.list != null) {
        walk_stmts(stmt.list, enclosing)
      }
      return
    }

    // While loop.
    if (stmt.kind == "while") {
      walk_expr(stmt.expression, enclosing, false)
      walk_stmts(stmt.statements, enclosing)
      return
    }

    // For loop.
    if (stmt.kind == "for") {
      walk_expr(stmt.init, enclosing, false)
      walk_expr(stmt.test, enclosing, false)
      walk_expr(stmt.update, enclosing, false)
      walk_stmts(stmt.statements, enclosing)
      return
    }

    // Do-while loop.
    if (stmt.kind == "do") {
      walk_stmts(stmt.statements, enclosing)
      walk_expr(stmt.expression, enclosing, false)
      return
    }

    // Return statement.
    if (stmt.kind == "return") {
      walk_expr(stmt.expression, enclosing, false)
      return
    }

    // Disrupt.
    if (stmt.kind == "disrupt") {
      walk_expr(stmt.expression, enclosing, false)
      return
    }

    // Block.
    if (stmt.kind == "block") {
      walk_stmts(stmt.statements, enclosing)
      return
    }

    // Fallthrough: walk any sub-nodes.
    walk_expr(stmt.expression, enclosing, false)
    walk_expr(stmt.left, enclosing, false)
    walk_expr(stmt.right, enclosing, false)
    walk_stmts(stmt.statements, enclosing)
  }

  // --- 1. Process named functions from ast.functions ---
  if (ast.functions != null) {
    _i = 0
    while (_i < length(ast.functions)) {
      fn = ast.functions[_i]
      sym_id = filename + ":" + (fn.name != null ? fn.name : "anon_" + text(fn.function_nr)) + ":fn"
      params_list = []
      if (fn.list != null) {
        _j = 0
        while (_j < length(fn.list)) {
          if (fn.list[_j].name != null) {
            params_list[] = fn.list[_j].name
          }
          _j = _j + 1
        }
      }

      symbols[] = {
        symbol_id: sym_id,
        name: fn.name,
        kind: "fn",
        decl_span: make_span(fn),
        doc_comment: find_doc_comment(fn.from_row),
        scope_fn_nr: fn.outer != null ? fn.outer : 0,
        params: params_list
      }

      // Record params as symbols.
      if (fn.list != null) {
        _j = 0
        while (_j < length(fn.list)) {
          if (fn.list[_j].name != null) {
            symbols[] = {
              symbol_id: filename + ":" + fn.list[_j].name + ":param",
              name: fn.list[_j].name,
              kind: "param",
              decl_span: make_span(fn.list[_j]),
              doc_comment: null,
              scope_fn_nr: fn.function_nr,
              params: null
            }
          }
          _j = _j + 1
        }
      }

      // Walk function body.
      walk_stmts(fn.statements, sym_id)
      walk_stmts(fn.disruption, sym_id)

      _i = _i + 1
    }
  }

  // --- 2. Walk top-level statements ---
  walk_stmts(ast.statements, null)

  // --- 3. Detect exports for .cm modules ---
  if (!is_actor && ast.statements != null) {
    _i = length(ast.statements) - 1
    while (_i >= 0) {
      if (ast.statements[_i].kind == "return" && ast.statements[_i].expression != null) {
        // Check if the return expression is a record literal with key-value pairs.
        if (ast.statements[_i].expression.list != null) {
          _j = 0
          while (_j < length(ast.statements[_i].expression.list)) {
            entry = ast.statements[_i].expression.list[_j]
            if (entry != null && entry.left != null && entry.left.name != null) {
              // Link the export to a symbol if the value is a name reference.
              sym_id = null
              if (entry.right != null && entry.right.kind == "name" && entry.right.function_nr != null) {
                sym_id = resolve_symbol_id(entry.right)
              }
              exports_list[] = {
                name: entry.left.name,
                symbol_id: sym_id
              }
            }
            _j = _j + 1
          }
        }
        break
      }
      _i = _i - 1
    }
  }

  // --- 4. Build reverse refs ---
  _i = 0
  while (_i < length(references)) {
    key = references[_i].name
    if (reverse[key] == null) {
      reverse[key] = []
    }
    reverse[key][] = {
      node_id: references[_i].node_id,
      span: references[_i].span,
      enclosing: references[_i].enclosing,
      ref_kind: references[_i].ref_kind
    }
    _i = _i + 1
  }

  return {
    version: 1,
    path: filename,
    is_actor: is_actor,
    imports: imports,
    symbols: symbols,
    references: references,
    call_sites: call_sites,
    exports: exports_list,
    reverse_refs: reverse
  }
}

// Run the full pipeline (tokenize -> parse -> fold) and index.
// pipeline is {tokenize, parse, fold} — pass fold as null to skip folding.
var index_file = function(src, filename, pipeline) {
  var tok_result = pipeline.tokenize(src, filename)
  var ast = pipeline.parse(tok_result.tokens, src, filename, pipeline.tokenize)
  if (pipeline.fold != null) {
    ast = pipeline.fold(ast)
  }
  return index_ast(ast, tok_result.tokens, filename)
}

return {
  index_file: index_file,
  index_ast: index_ast
}