module transform

import v3.flat

// transform_for_body transforms transform for body data for transform.
fn (mut t Transformer) transform_for_body(id flat.NodeId, node flat.Node) []flat.NodeId {
    if node.children_count < 3 {
        return arr1(id)
    }
    // child 0: init statement
    init_id := t.a.child(&node, 0)
    mut new_init := init_id
    if int(init_id) >= 0 {
        expanded := t.transform_stmt(init_id)
        if expanded.len > 0 {
            new_init = expanded[0]
        }
    }
    // child 1: condition expression
    cond_id := t.a.child(&node, 1)
    cond_smartcasts := t.extract_all_is_exprs(cond_id)
    new_cond := t.transform_and_chain_smartcasts(cond_id)
    mut cond_prefix := []flat.NodeId{}
    t.drain_pending(mut cond_prefix)
    // child 2: post statement
    post_id := t.a.child(&node, 2)
    mut new_post := post_id
    if int(post_id) >= 0 {
        expanded := t.transform_stmt(post_id)
        if expanded.len > 0 {
            new_post = expanded[0]
        }
    }
    // children 3..n: body statements
    mut body_ids := []flat.NodeId{}
    for i in 3 .. node.children_count {
        body_ids << t.a.child(&node, i)
    }
    for info in cond_smartcasts {
        t.push_smartcast(info.expr_name, info.variant_name, info.sum_type_name)
    }
    new_body := t.transform_stmts(body_ids)
    for _ in cond_smartcasts {
        t.pop_smartcast()
    }
    mut loop_cond := new_cond
    mut loop_body := new_body.clone()
    if cond_prefix.len > 0 {
        mut guarded_body := []flat.NodeId{cap: cond_prefix.len + new_body.len + 1}
        for stmt in cond_prefix {
            guarded_body << stmt
        }
        not_cond := t.make_prefix(.not, t.make_paren(new_cond))
        break_block := t.make_block(arr1(t.a.add(.break_stmt)))
        guarded_body << t.make_if(not_cond, break_block, t.make_block([]flat.NodeId{}))
        for stmt in new_body {
            guarded_body << stmt
        }
        loop_cond = t.make_bool_literal(true)
        loop_body = guarded_body.clone()
    }
    // Rebuild the for_stmt with transformed children
    start := t.a.children.len
    t.a.children << new_init
    t.a.children << loop_cond
    t.a.children << new_post
    for bid in loop_body {
        t.a.children << bid
    }
    count := t.a.children.len - start
    new_id := t.a.add_node(flat.Node{
        kind:           .for_stmt
        op:             node.op
        children_start: start
        children_count: flat.child_count(count)
        pos:            node.pos
        value:          node.value
        typ:            node.typ
    })
    return arr1(new_id)
}

// transform_for_in_body transforms transform for in body data for transform.
fn (mut t Transformer) transform_for_in_body(id flat.NodeId, node flat.Node) []flat.NodeId {
    header_count := node.value.int()
    if header_count < 3 || node.children_count < 3 {
        return arr1(id)
    }
    key_id := t.a.child(&node, 0) // loop var ident — pass through (do not transform a binding)
    val_id := t.a.child(&node, 1) // may be flat.empty_node (-1)
    container_id := t.a.child(&node, 2)
    iter_type := t.detect_for_in_type(node)
    has_index := int(val_id) >= 0
    container_is_range := if int(container_id) >= 0 {
        t.a.nodes[int(container_id)].kind == .range
    } else {
        false
    }
    if header_count == 4 {
        range_end_id := t.a.child(&node, 3)
        body_ids := t.a.children_of(&node)[header_count..].clone()
        return t.lower_range_for_in(id, node, key_id, container_id, range_end_id, body_ids)
    }
    if container_is_range {
        range_node := t.a.nodes[int(container_id)]
        if range_node.children_count >= 2 {
            body_ids := t.a.children_of(&node)[header_count..].clone()
            return t.lower_range_for_in(id, node, key_id, t.a.child(&range_node, 0), t.a.child(&range_node,
                1), body_ids)
        }
    }
    if iter_type.starts_with('map[') {
        return t.rebuild_for_in_stmt(id, node)
    }
    if pool_iter := t.pool_get_results_iter_type(container_id) {
        body_ids := t.a.children_of(&node)[header_count..].clone()
        return t.lower_indexed_for_in(id, node, key_id, val_id, container_id, pool_iter, has_index,
            body_ids)
    }
    effective_iter := if iter_type.starts_with('...') {
        '[]' + iter_type[3..]
    } else if iter_type.starts_with('&[]') {
        iter_type[1..]
    } else {
        iter_type
    }
    if effective_iter.starts_with('[]') || effective_iter == 'string'
        || t.is_fixed_array_type(effective_iter) {
        body_ids := t.a.children_of(&node)[header_count..].clone()
        return t.lower_indexed_for_in(id, node, key_id, val_id, container_id, effective_iter,
            has_index, body_ids)
    }
    return t.rebuild_for_in_stmt(id, node)
}

// pool_get_results_iter_type supports pool get results iter type handling for Transformer.
fn (t &Transformer) pool_get_results_iter_type(container_id flat.NodeId) ?string {
    if int(container_id) < 0 {
        return none
    }
    node := t.a.nodes[int(container_id)]
    if node.kind != .call || node.children_count == 0 {
        return none
    }
    callee_id := t.a.child(&node, 0)
    if int(callee_id) < 0 {
        return none
    }
    callee := t.a.nodes[int(callee_id)]
    if callee.kind != .index || callee.children_count < 2 {
        return none
    }
    base := t.a.child_node(&callee, 0)
    if base.kind != .selector || base.value !in ['get_results', 'get_results_ref'] {
        return none
    }
    elem_type := t.generic_call_type_arg_name(t.a.child(&callee, 1))
    if elem_type.len == 0 {
        return none
    }
    if base.value == 'get_results_ref' {
        return '[]&${elem_type}'
    }
    return '[]${elem_type}'
}

// rebuild_for_in_stmt supports rebuild for in stmt handling for Transformer.
fn (mut t Transformer) rebuild_for_in_stmt(_id flat.NodeId, node flat.Node) []flat.NodeId {
    header_count := node.value.int()
    key_id := t.a.child(&node, 0)
    val_id := t.a.child(&node, 1)
    container_id := t.a.child(&node, 2)
    new_container := t.transform_expr(container_id)
    iter_type := t.detect_for_in_type(node)
    has_index := int(val_id) >= 0
    container_is_range := if int(container_id) >= 0 {
        t.a.nodes[int(container_id)].kind == .range
    } else {
        false
    }
    if header_count == 4 || container_is_range {
        // range `for i in 0 .. n`: single loop var (child0) is an int
        if int(key_id) >= 0 {
            key_name := t.a.nodes[int(key_id)].value
            if key_name.len > 0 {
                t.set_var_type(key_name, 'int')
            }
        }
    } else if has_index {
        // two loop vars: child0 = key/index, child1 = value/element
        key_name := if int(key_id) >= 0 { t.a.nodes[int(key_id)].value } else { '' }
        val_name := if int(val_id) >= 0 { t.a.nodes[int(val_id)].value } else { '' }
        if iter_type.starts_with('map[') {
            // map[K]V: child0 (key) -> key type, child1 (val) -> value type
            bracket_end := iter_type.index(']') or { 0 }
            if key_name.len > 0 && bracket_end > 4 {
                t.set_var_type(key_name, iter_type[4..bracket_end])
            }
        } else if iter_type.starts_with('[]') || iter_type == 'string' {
            // []E: child0 (index) -> 'int'
            if key_name.len > 0 {
                t.set_var_type(key_name, 'int')
            }
        }
        if val_name.len > 0 {
            elem_type := t.infer_for_in_elem_type(iter_type, node)
            if elem_type.len > 0 {
                t.set_var_type(val_name, elem_type)
            }
        }
    } else {
        // single var, child0 is the element
        if int(key_id) >= 0 {
            key_name := t.a.nodes[int(key_id)].value
            if key_name.len > 0 {
                elem_type := t.infer_for_in_elem_type(iter_type, node)
                if elem_type.len > 0 {
                    t.set_var_type(key_name, elem_type)
                }
            }
        }
    }

    mut ids := []flat.NodeId{}
    ids << key_id
    ids << val_id
    ids << new_container
    if header_count == 4 {
        range_end_id := t.a.child(&node, 3)
        ids << t.transform_expr(range_end_id)
    }
    body_ids := t.a.children_of(&node)[header_count..].clone()
    new_body := t.transform_stmts(body_ids)
    for bid in new_body {
        ids << bid
    }
    start := t.a.children.len
    for cid in ids {
        t.a.children << cid
    }
    return arr1(t.a.add_node(flat.Node{
        kind:           .for_in_stmt
        op:             node.op
        children_start: start
        children_count: flat.child_count(ids.len)
        pos:            node.pos
        value:          node.value
        typ:            node.typ
    }))
}

// lower_range_for_in builds lower range for in data for transform.
fn (mut t Transformer) lower_range_for_in(id flat.NodeId, node flat.Node, key_id flat.NodeId, low_id flat.NodeId, high_id flat.NodeId, body_ids []flat.NodeId) []flat.NodeId {
    if int(key_id) < 0 {
        return arr1(id)
    }
    key := t.a.nodes[int(key_id)]
    if key.kind != .ident || key.value.len == 0 {
        return arr1(id)
    }
    t.set_var_type(key.value, 'int')
    low := t.transform_expr(low_id)
    high := t.stable_expr_for_reuse(high_id)
    mut prefix := []flat.NodeId{}
    t.drain_pending(mut prefix)
    init := t.make_decl_assign_typed(key.value, low, 'int')
    cond := t.make_infix(.lt, t.make_ident(key.value), high)
    post := t.make_expr_stmt(t.make_postfix(t.make_ident(key.value), .inc))
    new_body := t.transform_stmts(body_ids)
    prefix << t.make_for_stmt(init, cond, post, new_body, node)
    return prefix
}

// lower_indexed_for_in builds lower indexed for in data for transform.
fn (mut t Transformer) lower_indexed_for_in(id flat.NodeId, node flat.Node, key_id flat.NodeId, val_id flat.NodeId, container_id flat.NodeId, iter_type string, has_index bool, body_ids []flat.NodeId) []flat.NodeId {
    if int(key_id) < 0 {
        return arr1(id)
    }
    key := t.a.nodes[int(key_id)]
    if key.kind != .ident || key.value.len == 0 {
        return arr1(id)
    }
    mut container := t.stable_expr_for_reuse(container_id)
    mut prefix := []flat.NodeId{}
    t.drain_pending(mut prefix)
    mut actual_iter_type := iter_type
    container_type := t.node_type(container)
    if container_type.len > 0 && !for_iter_type_has_generic_placeholder(actual_iter_type)
        && !(t.is_fixed_array_type(actual_iter_type) && !t.is_fixed_array_type(container_type)) {
        actual_iter_type = container_type
    }
    if actual_iter_type.starts_with('&[]') {
        container = t.make_prefix(.mul, container)
        t.a.nodes[int(container)].typ = actual_iter_type[1..]
        actual_iter_type = actual_iter_type[1..]
    }
    elem_type := t.infer_for_in_elem_type(actual_iter_type, node)
    if elem_type.len == 0 {
        return arr1(id)
    }
    mut idx_name := key.value
    if !has_index {
        idx_name = t.new_temp('for_idx')
    }
    mut elem_name := key.value
    if has_index {
        if int(val_id) < 0 {
            return arr1(id)
        }
        val := t.a.nodes[int(val_id)]
        if val.kind != .ident || val.value.len == 0 {
            return arr1(id)
        }
        elem_name = val.value
    }
    t.set_var_type(idx_name, 'int')
    elem_is_mut := node.op == .amp && actual_iter_type != 'string'
    elem_needs_ref := elem_is_mut && !elem_type.starts_with('&')
    elem_var_type := if elem_needs_ref { '&${elem_type}' } else { elem_type }
    t.set_var_type(elem_name, elem_var_type)
    len_expr := if t.is_fixed_array_type(actual_iter_type) {
        t.make_for_in_fixed_array_len_expr(actual_iter_type)
    } else {
        t.make_selector(container, 'len', 'int')
    }
    init := t.make_decl_assign_typed(idx_name, t.make_int_literal(0), 'int')
    cond := t.make_infix(.lt, t.make_ident(idx_name), len_expr)
    post := t.make_expr_stmt(t.make_postfix(t.make_ident(idx_name), .inc))
    elem_expr := if elem_needs_ref && actual_iter_type.starts_with('[]') {
        t.array_get_ptr(container, t.make_ident(idx_name), elem_type)
    } else if elem_needs_ref {
        t.make_prefix(.amp, t.make_index(container, t.make_ident(idx_name), elem_type))
    } else if actual_iter_type.starts_with('[]') {
        t.array_get_value(container, t.make_ident(idx_name), elem_type)
    } else {
        t.make_index(container, t.make_ident(idx_name), elem_type)
    }
    elem_decl := t.make_decl_assign_typed(elem_name, elem_expr, elem_var_type)
    mut transformed_body := []flat.NodeId{}
    if elem_needs_ref {
        had_pointer_value_lvalue := t.pointer_value_lvalues[elem_name] or { false }
        t.pointer_value_lvalues[elem_name] = true
        transformed_body = t.transform_stmts(body_ids)
        if had_pointer_value_lvalue {
            t.pointer_value_lvalues[elem_name] = true
        } else {
            t.pointer_value_lvalues.delete(elem_name)
        }
    } else {
        transformed_body = t.transform_stmts(body_ids)
    }
    mut new_body := []flat.NodeId{}
    new_body << elem_decl
    new_body << transformed_body
    prefix << t.make_for_stmt(init, cond, post, new_body, node)
    return prefix
}

// make_for_stmt builds make for stmt data for transform.
fn (mut t Transformer) make_for_stmt(init flat.NodeId, cond flat.NodeId, post flat.NodeId, body []flat.NodeId, src flat.Node) flat.NodeId {
    start := t.a.children.len
    t.a.children << init
    t.a.children << cond
    t.a.children << post
    for id in body {
        t.a.children << id
    }
    return t.a.add_node(flat.Node{
        kind:           .for_stmt
        op:             src.op
        children_start: start
        children_count: flat.child_count(3 + body.len)
        pos:            src.pos
        typ:            src.typ
    })
}

// detect_for_in_type resolves detect for in type information for transform.
fn (mut t Transformer) detect_for_in_type(node flat.Node) string {
    if node.typ.len > 0 {
        return node.typ
    }
    header_count := node.value.int()
    container_idx := if header_count >= 3 { header_count - 1 } else { 2 }
    if node.children_count > container_idx {
        iter_id := t.a.child(&node, container_idx)
        if fixed_array_type := t.detect_for_in_global_fixed_array_type(iter_id) {
            return fixed_array_type
        }
        return t.node_type(iter_id)
    }
    return ''
}

fn (t &Transformer) detect_for_in_global_fixed_array_type(id flat.NodeId) ?string {
    if int(id) < 0 {
        return none
    }
    node := t.a.nodes[int(id)]
    if node.kind != .ident || node.value.len == 0 {
        return none
    }
    if t.var_type(node.value).len > 0 {
        return none
    }
    mut candidates := []string{}
    if t.cur_module.len > 0 && t.cur_module != 'main' && t.cur_module != 'builtin' {
        candidates << '${t.cur_module}.${node.value}'
    }
    candidates << node.value
    for candidate in candidates {
        if typ := t.globals[candidate] {
            normalized := t.normalize_type_alias(typ)
            if t.is_fixed_array_type(normalized) {
                return normalized
            }
        }
    }
    if !isnil(t.tc) {
        checker_type := t.normalize_type_alias(t.tc.resolve_type(id).name())
        if t.is_fixed_array_type(checker_type) {
            return checker_type
        }
    }
    return none
}

fn for_iter_type_has_generic_placeholder(iter_type string) bool {
    clean := iter_type.trim_space()
    if clean.len == 0 {
        return false
    }
    if is_generic_placeholder_type_name(clean) {
        return true
    }
    if clean.starts_with('&') {
        return for_iter_type_has_generic_placeholder(clean[1..])
    }
    if clean.starts_with('[]') {
        return for_iter_type_has_generic_placeholder(clean[2..])
    }
    if clean.starts_with('map[') {
        bracket_end := clean.index(']') or { return false }
        return for_iter_type_has_generic_placeholder(clean[4..bracket_end])
            || for_iter_type_has_generic_placeholder(clean[bracket_end + 1..])
    }
    if clean.starts_with('[') {
        bracket_end := clean.index(']') or { return false }
        return for_iter_type_has_generic_placeholder(clean[bracket_end + 1..])
    }
    return false
}

// Infer the element type for the loop variable from the iterable type.
fn (t &Transformer) infer_for_in_elem_type(iter_type string, node flat.Node) string {
    if iter_type.starts_with('&[]') {
        return iter_type[3..]
    }
    if iter_type.starts_with('[]') {
        return iter_type[2..]
    }
    if iter_type.starts_with('map[') {
        // map[K]V -> value type is everything after the closing ']'
        bracket_end := iter_type.index(']') or { return '' }
        if bracket_end + 1 < iter_type.len {
            return iter_type[bracket_end + 1..]
        }
        return ''
    }
    if iter_type == 'string' {
        return 'u8'
    }
    if t.is_fixed_array_type(iter_type) {
        return for_in_fixed_array_elem_type(iter_type)
    }
    // Check if the iterable is a range expression
    if node.children_count > 0 {
        iter_id := t.a.child(&node, 0)
        iter_node := t.a.nodes[int(iter_id)]
        if iter_node.kind == .range {
            return 'int'
        }
    }
    return ''
}

fn (mut t Transformer) make_for_in_fixed_array_len_expr(s string) flat.NodeId {
    len_text := for_in_fixed_array_len_text(s)
    if is_decimal_text(len_text) {
        return t.make_int_literal(len_text.int())
    }
    if !isnil(t.tc) {
        if v := t.tc.const_int_value(len_text, []string{}) {
            return t.make_int_literal(v)
        }
    }
    if len_text.contains('.') {
        base := len_text.all_before_last('.')
        field := len_text.all_after_last('.')
        return t.make_selector(t.make_ident(base), field, 'int')
    }
    return t.make_ident(len_text)
}

fn for_in_fixed_array_elem_type(s string) string {
    clean := s.trim_space()
    if clean.starts_with('[') {
        return clean.all_after(']')
    }
    open := clean.last_index_u8(`[`)
    if open < 0 {
        return ''
    }
    return clean[..open]
}

fn for_in_fixed_array_len_text(s string) string {
    clean := s.trim_space()
    if clean.starts_with('[') {
        return clean.all_after('[').all_before(']').trim_space()
    }
    open := clean.last_index_u8(`[`)
    if open < 0 {
        return ''
    }
    close_rel := clean[open + 1..].index_u8(`]`)
    if close_rel < 0 {
        return ''
    }
    return clean[open + 1..open + 1 + close_rel].trim_space()
}