package findr

import "core:fmt"
import "core:os"
import "core:strings"
import "core:sync"
import "core:sys/linux"
import "core:text/regex"
import "core:thread"

IgnoreMode :: enum {
	Respected, // skip gitignored, prune ignored dirs (fd -H default)
	All,       // ignore .gitignore entirely, descend everywhere (fd -HI)
	Ignored,   // emit ONLY gitignored files, prune ignored dirs (findr original)
}

WalkOptions :: struct {
	pattern:        string,  // regex on basename; "" = match all
	excludes:       []string, // glob patterns to skip entirely (fd -E)
	include_hidden: bool,    // true = include dotfiles (fd -H)
	ignore_mode:    IgnoreMode,
}

RawEntry :: struct {
	name: string,
	type: linux.Dirent_Type,
}

GIContext :: struct {
	gi:       ^Gitignore,   // nil if this dir had no .gitignore
	base_rel: string,       // relative path from repo root to this dir
	parent:   ^GIContext,   // parent context (nil if repo root)
}

WorkItem :: struct {
	path:    string,        // absolute directory path
	rel:     string,        // relative path from repo root ("" = root)
	gi_ctx:  ^GIContext,    // gitignore chain (nil = outside any repo)
	in_repo: bool,          // true if inside a git repo
}

WalkerPool :: struct {
	queue:         [dynamic]WorkItem,
	queue_mutex:   sync.Mutex,
	queue_sema:    sync.Atomic_Sema,
	results:       ^[dynamic]string,
	results_mutex: sync.Mutex,
	active:        i64,
	done:          sync.One_Shot_Event,
	threads:       [dynamic]^thread.Thread,
	opts:          WalkOptions,
	pattern_re:    regex.Regular_Expression,
	has_pattern:   bool,
	exclude_gi:    ^Gitignore,
	all_contexts:  [dynamic]^GIContext,
	contexts_lock: sync.Mutex,
}

walk :: proc(roots: []string, results: ^[dynamic]string, opts: WalkOptions, thread_count: int) {
	if len(roots) == 0 do return

	pool := new(WalkerPool)
	pool.queue = make([dynamic]WorkItem)
	pool.results = results
	pool.active = i64(len(roots))
	pool.threads = make([dynamic]^thread.Thread)
	pool.all_contexts = make([dynamic]^GIContext)
	pool.opts = opts
	pool.exclude_gi = nil
	pool.has_pattern = false

	if len(opts.pattern) > 0 {
		re, err := regex.create(opts.pattern, {regex.Flag.No_Capture})
		if err == nil {
			pool.pattern_re = re
			pool.has_pattern = true
		}
	}

	if len(opts.excludes) > 0 {
		sb: strings.Builder
		strings.builder_init(&sb)
		for ex in opts.excludes {
			fmt.sbprintf(&sb, "%s\n", ex)
		}
		content := strings.to_string(sb)
		pool.exclude_gi = new(Gitignore)
		pool.exclude_gi^ = parse(content)
		strings.builder_destroy(&sb)
	}

	for root in roots {
		root_clone, _ := strings.clone(root)
		append(&pool.queue, WorkItem{path = root_clone})
		sync.atomic_sema_post(&pool.queue_sema)
	}

	for i in 0 ..< thread_count {
		t := thread.create(walk_worker)
		t.data = rawptr(pool)
		t.init_context = context
		thread.start(t)
		append(&pool.threads, t)
	}

	sync.one_shot_event_wait(&pool.done)

	for _ in 0 ..< thread_count {
		sync.atomic_sema_post(&pool.queue_sema)
	}

	for t in pool.threads {
		thread.destroy(t)
	}
	delete(pool.threads)
	for item in pool.queue {
		delete(item.path)
		if len(item.rel) > 0 { delete(item.rel) }
	}
	delete(pool.queue)

	for ctx in pool.all_contexts {
		if ctx.gi != nil {
			destroy(ctx.gi)
			free(ctx.gi)
		}
		if len(ctx.base_rel) > 0 {
			delete(ctx.base_rel)
		}
		free(ctx)
	}
	delete(pool.all_contexts)

	if pool.has_pattern {
		regex.destroy(pool.pattern_re)
	}
	if pool.exclude_gi != nil {
		destroy(pool.exclude_gi)
		free(pool.exclude_gi)
	}

	free(pool)
}

walk_worker :: proc(t: ^thread.Thread) {
	pool := cast(^WalkerPool)t.data

	for {
		sync.atomic_sema_wait(&pool.queue_sema)

		sync.mutex_lock(&pool.queue_mutex)
		if len(pool.queue) == 0 {
			sync.mutex_unlock(&pool.queue_mutex)
			if sync.atomic_load_explicit(&pool.active, .Acquire) == 0 {
				sync.one_shot_event_signal(&pool.done)
			}
			break
		}
		last := len(pool.queue) - 1
		item := pool.queue[last]
		ordered_remove(&pool.queue, last)
		sync.mutex_unlock(&pool.queue_mutex)

		process_dir(pool, item)
		delete(item.path)
		if len(item.rel) > 0 { delete(item.rel) }

		old := sync.atomic_sub_explicit(&pool.active, 1, .Release)
		if old == 1 {
			sync.one_shot_event_signal(&pool.done)
		}
	}
}

process_dir :: proc(pool: ^WalkerPool, item: WorkItem) {
	dir_path := item.path
	has_git := false
	entries := read_dir_entries(dir_path, &has_git)
	defer free_entries(&entries)

	gi_ctx := item.gi_ctx
	rel := item.rel

	if has_git {
		gi_ctx = nil
		rel = ""
	}

	child_in_repo := has_git || item.in_repo

	gi := load_ignore_patterns(dir_path, child_in_repo)
	if gi != nil {
		new_ctx := new(GIContext)
		new_ctx.gi = gi
		if len(rel) > 0 {
			new_ctx.base_rel, _ = strings.clone(rel)
		}
		new_ctx.parent = gi_ctx

		sync.mutex_lock(&pool.contexts_lock)
		append(&pool.all_contexts, new_ctx)
		sync.mutex_unlock(&pool.contexts_lock)

		gi_ctx = new_ctx
	}

	rel_buf: [4096]u8

	for entry in entries {
		if entry.name == ".git" do continue

		is_dir := entry.type == .DIR
		is_nondir := entry.type != .DIR

		if pool.exclude_gi != nil && is_ignored(pool.exclude_gi, entry.name, is_dir) {
			continue
		}

		if !pool.opts.include_hidden && len(entry.name) > 0 && entry.name[0] == '.' {
			continue
		}

		entry_rel := build_rel(rel_buf[:], rel, entry.name)

		ignored := false
		if gi_ctx != nil && pool.opts.ignore_mode != .All {
			ignored = check_chain(gi_ctx, entry_rel, is_dir)
		}

		should_emit: bool
		if ignored {
			should_emit = pool.opts.ignore_mode == .Ignored
		} else {
			should_emit = pool.opts.ignore_mode != .Ignored
		}

		if is_dir {
			if should_emit && matches_pattern(pool, entry.name) {
				dir_path_out := join_path_dir(dir_path, entry.name)
				sync.mutex_lock(&pool.results_mutex)
				append(pool.results, dir_path_out)
				sync.mutex_unlock(&pool.results_mutex)
			}
			if !ignored {
				child_rel, _ := strings.clone(entry_rel)
				child_path := join_path(dir_path, entry.name)
				push_work(pool, WorkItem{path = child_path, rel = child_rel, gi_ctx = gi_ctx, in_repo = child_in_repo})
			}
		} else if is_nondir {
			if should_emit && matches_pattern(pool, entry.name) {
				full_path := join_path(dir_path, entry.name)
				sync.mutex_lock(&pool.results_mutex)
				append(pool.results, full_path)
				sync.mutex_unlock(&pool.results_mutex)
			}
		}
	}
}

check_chain :: proc(ctx: ^GIContext, entry_rel: string, is_dir: bool) -> bool {
	c := ctx
	for c != nil {
		if c.gi != nil {
			rel := relative_to(entry_rel, c.base_rel)
			match := check_match(c.gi, rel, is_dir)
			if match != .None {
				return match == .Ignored
			}
		}
		c = c.parent
	}
	return false
}

relative_to :: proc(entry_rel, base_rel: string) -> string {
	if len(base_rel) == 0 do return entry_rel
	prefix_len := len(base_rel)
	if len(entry_rel) > prefix_len && entry_rel[prefix_len] == '/' &&
	   strings.has_prefix(entry_rel, base_rel) {
		return entry_rel[prefix_len + 1:]
	}
	return entry_rel
}

build_rel :: proc(buf: []u8, rel, name: string) -> string {
	if len(rel) == 0 do return name
	pos := copy(buf, rel)
	if pos < len(buf) {
		buf[pos] = '/'
		pos += 1
		pos += copy(buf[pos:], name)
	}
	return string(buf[:pos])
}

matches_pattern :: proc(pool: ^WalkerPool, name: string) -> bool {
	if !pool.has_pattern do return true
	cap, ok := regex.match(pool.pattern_re, name)
	regex.destroy(cap)
	return ok
}

push_work :: proc(pool: ^WalkerPool, item: WorkItem) {
	sync.atomic_add_explicit(&pool.active, 1, .Relaxed)
	sync.mutex_lock(&pool.queue_mutex)
	append(&pool.queue, item)
	sync.mutex_unlock(&pool.queue_mutex)
	sync.atomic_sema_post(&pool.queue_sema)
}

read_dir_entries :: proc(dir_path: string, has_git: ^bool) -> [dynamic]RawEntry {
	entries := make([dynamic]RawEntry)

	cpath := strings.clone_to_cstring(dir_path)
	if cpath == nil do return entries

	fd, err := linux.open(cpath, {.DIRECTORY, .CLOEXEC})
	delete(cpath)
	if err != .NONE do return entries

	buf: [8192]u8
	has_git^ = false

	for {
		n, errno := linux.getdents(fd, buf[:])
		if n <= 0 || errno != .NONE do break

		offs := 0
		for d in linux.dirent_iterate_buf(buf[:n], &offs) {
			name := linux.dirent_name(d)
			if name == "." || name == ".." do continue

			if name == ".git" && d.type == .DIR {
				has_git^ = true
			}

			cloned := strings.clone(name)
			append(&entries, RawEntry{name = cloned, type = d.type})
		}
	}

	linux.close(fd)
	return entries
}

free_entries :: proc(entries: ^[dynamic]RawEntry) {
	for &entry in entries {
		delete(entry.name)
	}
	delete(entries^)
}

load_ignore_patterns :: proc(dir_path: string, in_repo: bool) -> ^Gitignore {
	has_patterns := false
	sb: strings.Builder
	strings.builder_init(&sb)
	defer strings.builder_destroy(&sb)

	if in_repo {
		gi_path := join_path(dir_path, ".gitignore")
		data, err := os.read_entire_file_from_path(gi_path, context.allocator)
		delete(gi_path)
		if err == .NONE {
			fmt.sbprintf(&sb, "%s", string(data))
			delete(data)
			has_patterns = true
		}
	}

	ig_path := join_path(dir_path, ".ignore")
	idata, ierr := os.read_entire_file_from_path(ig_path, context.allocator)
	delete(ig_path)
	if ierr == .NONE {
		fmt.sbprintf(&sb, "%s", string(idata))
		delete(idata)
		has_patterns = true
	}

	if !has_patterns do return nil

	content := strings.to_string(sb)
	gi := new(Gitignore)
	gi^ = parse(content)
	return gi
}

join_path :: proc(parent, child: string) -> string {
	b: strings.Builder
	strings.builder_init(&b)
	defer strings.builder_destroy(&b)

	fmt.sbprintf(&b, "%s", parent)
	if len(parent) == 0 || parent[len(parent) - 1] != '/' {
		fmt.sbprintf(&b, "/")
	}
	fmt.sbprintf(&b, "%s", child)

	s := strings.to_string(b)
	result, _ := strings.clone(s)
	return result
}

join_path_dir :: proc(parent, child: string) -> string {
	b: strings.Builder
	strings.builder_init(&b)
	defer strings.builder_destroy(&b)

	fmt.sbprintf(&b, "%s", parent)
	if len(parent) == 0 || parent[len(parent) - 1] != '/' {
		fmt.sbprintf(&b, "/")
	}
	fmt.sbprintf(&b, "%s/", child)

	s := strings.to_string(b)
	result, _ := strings.clone(s)
	return result
}