package compiler

import "./checker"
import "./cimport"
import "./hir"
import "./linker"
import "./loader"
import "./source"
import "./symbol"
import "./target"
import "./types"
import "core:fmt"
import vmem "core:mem/virtual"
import "core:os"
import "core:os/os2"
import "core:path/filepath"
import "core:strings"

// BuildConfig is the native, extracted form of std/build's BuildConfig: all
// strings are cloned into context.allocator so they outlive the build module's
// arena (freed at the end of run_build). Free with destroy_build_config.
BuildConfig :: struct {
	output_name:    string,
	source_dir:     string,
	link_arguments: []linker.Argument,
	c_options:      cimport.Options,
}

destroy_build_config :: proc(cfg: ^BuildConfig) {
	delete(cfg.output_name)
	delete(cfg.source_dir)
	for arg in cfg.link_arguments {
		delete(arg.value)
	}
	delete(cfg.link_arguments)
	for path in cfg.c_options.include_paths {
		delete(path)
	}
	delete(cfg.c_options.include_paths)
	for define in cfg.c_options.defines {
		delete(define)
	}
	delete(cfg.c_options.defines)
}

// run_build implements `brolang build [root]`: it loads and type-checks
// `root/build.bro`, reads its `config` constant, and compiles the program
// package the config names. build.bro is only checked (never lowered/emitted),
// so the config is read straight from the HIR.
run_build :: proc(root: string) -> int {
	project_root := root
	owns_project_root := false
	if len(project_root) == 0 {
		found_root, found := find_build_root()
		if !found {
			fmt.eprintln("brolang build: could not find build.bro in the current directory or any parent")
			return 2
		}
		project_root = found_root
		owns_project_root = true
	}
	defer if owns_project_root {
		delete(project_root)
	}

	sources := source.init_store()
	defer source.destroy_store(&sources)
	diagnostics := source.init_store_diagnostics(&sources)
	defer source.destroy_diagnostics(&diagnostics)
	symbols := symbol.init_table()
	defer symbol.destroy_table(&symbols)

	arena: vmem.Arena
	if err := vmem.arena_init_growing(&arena); err != nil {
		fmt.eprintln("failed to initialize build arena:", err)
		return 2
	}
	defer vmem.arena_destroy(&arena)
	a := vmem.arena_allocator(&arena)

	ast_module, loaded := loader.load(project_root, &sources, &diagnostics, &symbols, a, a, cimport.Options{}, target.DEFAULT, project_root)
	if !loaded {
		source.print_all(&diagnostics)
		fmt.eprintln("failed to load build root:", project_root)
		return 2
	}
	// check needs no `main`: it synthesizes a trap main and emits one benign
	// "missing main" diagnostic, which is expected for build.bro. Suppress that
	// one but surface any real errors in build.bro (and fail on them).
	hir_module := checker.check(&ast_module, &diagnostics, &symbols, target.DEFAULT, a)
	if build_bro_has_errors(&diagnostics) {
		source.print_all(&diagnostics)
		return 2
	}

	cfg, ok := extract_build_config(&hir_module, &symbols)
	if !ok {
		return 2
	}
	defer destroy_build_config(&cfg)

	program := filepath.join({project_root, cfg.source_dir})
	defer delete(program)
	output, output_ok := build_output_path(project_root, cfg.output_name)
	if !output_ok {
		return 2
	}
	defer delete(output)
	return compile_package(program, output, cfg.link_arguments, target.DEFAULT, cfg.c_options, project_root)
}

valid_output_name :: proc(name: string) -> bool {
	return len(name) > 0 && name != "." && name != ".." &&
	       !strings.contains(name, "/") && !strings.contains(name, "\\")
}

build_output_path :: proc(project_root, name: string, allocator := context.allocator) -> (string, bool) {
	if !valid_output_name(name) {
		fmt.eprintfln("build.bro: config 'name' must be a plain executable name, got '%s'", name)
		return "", false
	}
	build_dir, dir_error := filepath.join({project_root, "build"}, allocator)
	if dir_error != nil {
		return "", false
	}
	if os.exists(build_dir) {
		if !os.is_dir(build_dir) {
			fmt.eprintfln("build path exists and is not a directory: %s", build_dir)
			delete(build_dir, allocator)
			return "", false
		}
	} else if err := os2.make_directory_all(build_dir); err != nil {
		fmt.eprintfln("failed to create build directory '%s': %v", build_dir, err)
		delete(build_dir, allocator)
		return "", false
	}
	output, output_error := filepath.join({build_dir, name}, allocator)
	delete(build_dir, allocator)
	if output_error != nil {
		return "", false
	}
	return output, true
}

find_build_root :: proc(allocator := context.allocator) -> (string, bool) {
	current := os.get_current_directory(allocator)
	if len(current) == 0 {
		return "", false
	}
	defer delete(current, allocator)
	return find_build_root_from(current, allocator)
}

find_build_root_from :: proc(start: string, allocator := context.allocator) -> (string, bool) {
	current, current_ok := filepath.abs(start, allocator)
	if !current_ok {
		current = strings.clone(start, allocator)
	}
	for {
		build_path, build_error := filepath.join({current, "build.bro"}, allocator)
		if build_error != nil {
			delete(current, allocator)
			return "", false
		}
		found := os.exists(build_path)
		delete(build_path, allocator)
		if found {
			return current, true
		}
		if current == "/" {
			delete(current, allocator)
			return "", false
		}
		parent := filepath.dir(current, allocator)
		if parent == current {
			delete(parent, allocator)
			delete(current, allocator)
			return "", false
		}
		delete(current, allocator)
		current = parent
	}
}

// build_bro_has_errors reports whether checking build.bro produced any diagnostic
// other than the benign "missing or unusable main function" (build.bro has no
// main by design; that one is emitted with an empty span).
build_bro_has_errors :: proc(diagnostics: ^source.Diagnostics) -> bool {
	for item in diagnostics.items {
		if item.span == (source.Span{}) && item.message == "missing or unusable main function" {
			continue
		}
		return true
	}
	return false
}

// extract_build_config finds the top-level `config` constant and reads its
// BuildConfig{...} fields out of the HIR. All returned strings are cloned into
// context.allocator.
extract_build_config :: proc(m: ^hir.Module, symbols: ^symbol.Table) -> (BuildConfig, bool) {
	config_id := symbol.intern(symbols, "config")
	config_expr := hir.INVALID_EXPR
	found := false
	for g in m.globals {
		if g.name == config_id {
			config_expr = g.expr
			found = true
			break
		}
	}
	if !found {
		fmt.eprintln("build.bro: missing top-level 'config' constant")
		return {}, false
	}
	root := unwrap_coercions(m, config_expr)
	if root == hir.INVALID_EXPR || m.exprs[root].kind != .Struct {
		fmt.eprintln("build.bro: 'config' must be a BuildConfig{...} literal")
		return {}, false
	}
	args := m.exprs[root].args
	fields := types.fields_for(&m.types, m.exprs[root].type)

	cfg: BuildConfig
	links: [dynamic]linker.Argument
	includes: [dynamic]string
	defines: [dynamic]string

	for field, i in fields {
		if i >= len(args) {
			break
		}
		switch symbol.resolve(symbols, symbol.Id(field.name)) {
		case "name":
			if s, sok := read_string(m, args[i]); sok {
				cfg.output_name = strings.clone(s)
			}
		case "source":
			if s, sok := read_string(m, args[i]); sok {
				cfg.source_dir = strings.clone(s)
			}
		case "libraries":
			list := read_string_list(m, args[i])
			for v in list {
				append(&links, linker.Argument{kind = .Library, value = strings.clone(v)})
			}
			delete(list)
		case "lib_paths":
			list := read_string_list(m, args[i])
			for v in list {
				append(&links, linker.Argument{kind = .Library_Path, value = strings.clone(v)})
			}
			delete(list)
		case "links":
			list := read_string_list(m, args[i])
			for v in list {
				append(&links, linker.Argument{kind = .Input, value = strings.clone(v)})
			}
			delete(list)
		case "includes":
			list := read_string_list(m, args[i])
			for v in list {
				append(&includes, strings.clone(v))
			}
			delete(list)
		case "defines":
			list := read_string_list(m, args[i])
			for v in list {
				append(&defines, strings.clone(v))
			}
			delete(list)
		}
	}

	cfg.link_arguments = links[:]
	cfg.c_options.include_paths = includes[:]
	cfg.c_options.defines = defines[:]

	if len(cfg.output_name) == 0 || len(cfg.source_dir) == 0 {
		fmt.eprintln("build.bro: config requires non-empty 'name' and 'source'")
		destroy_build_config(&cfg)
		return {}, false
	}
	return cfg, true
}

// unwrap_coercions strips implicit coercion wrappers (each stores its inner
// expr in `.left`) to reach the underlying value expression.
unwrap_coercions :: proc(m: ^hir.Module, id: hir.Expr_Id) -> hir.Expr_Id {
	cur := id
	for cur != hir.INVALID_EXPR && int(cur) < len(m.exprs) {
		#partial switch m.exprs[cur].kind {
		case .Retype, .Pointer_Cast, .Weaken_Slice, .Weaken_Pointer, .Decay_Array_Pointer, .Slice_Ptr,
		     .Widen, .Sum_Widen, .Optional_Some, .C_Coerce, .Scalar_Cast:
			cur = m.exprs[cur].left
		case:
			return cur
		}
	}
	return cur
}

read_string :: proc(m: ^hir.Module, id: hir.Expr_Id) -> (string, bool) {
	e := unwrap_coercions(m, id)
	if e == hir.INVALID_EXPR || m.exprs[e].kind != .String {
		return "", false
	}
	sid := m.exprs[e].integer
	if sid < 0 || int(sid) >= len(m.strings) {
		return "", false
	}
	return m.strings[int(sid)], true
}

// read_string_list reads a `&[...]` list field: the value is an address of an
// anonymous global array (see checker `&<array literal>` promotion), whose
// elements are strings. Returned strings alias m.strings; callers clone them.
// The returned slice is owned by the caller (delete it).
read_string_list :: proc(m: ^hir.Module, id: hir.Expr_Id) -> []string {
	addr := unwrap_coercions(m, id)
	if addr == hir.INVALID_EXPR || m.exprs[addr].kind != .Address {
		return nil
	}
	g := unwrap_coercions(m, m.exprs[addr].left)
	if g == hir.INVALID_EXPR || m.exprs[g].kind != .Global {
		return nil
	}
	gid := hir.as_global(m.exprs[g].target)
	if gid == hir.INVALID_GLOBAL || int(gid) >= len(m.globals) {
		return nil
	}
	arr := m.globals[gid].expr
	if arr == hir.INVALID_EXPR || m.exprs[arr].kind != .Array {
		return nil
	}
	elems := m.exprs[arr].args
	out := make([]string, len(elems))
	for a, i in elems {
		s, ok := read_string(m, a)
		if !ok {
			delete(out)
			return nil
		}
		out[i] = s
	}
	return out
}