package config

import (
	"os"
	"path/filepath"
	"runtime"
	"strings"
)

// ResolveRoot returns the absolute workspace root path.
// Reads CTASK_ROOT env var, falls back to ~/ai-workspaces (or %USERPROFILE%\ai-workspaces on Windows).
func ResolveRoot() string {
	root := os.Getenv("CTASK_ROOT")
	if root == "" {
		home, _ := os.UserHomeDir()
		return filepath.Join(home, "ai-workspaces")
	}
	return expandPath(root)
}

// ResolveAgent returns the agent command.
// Reads CTASK_AGENT env var, falls back to "claude".
func ResolveAgent() string {
	agent := os.Getenv("CTASK_AGENT")
	if agent == "" {
		return "claude"
	}
	return agent
}

// ResolveSeedDir returns the user general seed directory.
// Reads CTASK_SEED_DIR; falls back to %APPDATA%\ctask\seed on Windows or
// ~/.config/ctask/seed on Unix.
func ResolveSeedDir() string {
	if v := os.Getenv("CTASK_SEED_DIR"); v != "" {
		return expandPath(v)
	}
	return defaultSeedDir("seed")
}

// ResolveProjectSeedDir returns the user project seed directory.
// Reads CTASK_SEED_PROJECT_DIR; falls back to %APPDATA%\ctask\seed-project on Windows
// or ~/.config/ctask/seed-project on Unix.
func ResolveProjectSeedDir() string {
	if v := os.Getenv("CTASK_SEED_PROJECT_DIR"); v != "" {
		return expandPath(v)
	}
	return defaultSeedDir("seed-project")
}

// ResolveProjectRoot returns the project workspace root override.
// Returns empty string if CTASK_PROJECT_ROOT is not set; callers should fall back
// to ResolveRoot() in that case.
func ResolveProjectRoot() string {
	v := os.Getenv("CTASK_PROJECT_ROOT")
	if v == "" {
		return ""
	}
	return expandPath(v)
}

// SearchRoots returns the deduplicated list of workspace roots that all query
// and listing operations must consult. Always includes CTASK_ROOT. When
// CTASK_PROJECT_ROOT is set, adds that (unless it duplicates CTASK_ROOT).
// When CTASK_PROJECT_ROOT is unset, adds $CTASK_ROOT/projects/ so that
// projects created under the default category are discoverable from any
// shell without per-session env var setup.
func SearchRoots() []string {
	taskRoot := ResolveRoot()
	roots := []string{taskRoot}
	seen := map[string]struct{}{searchRootKey(taskRoot): {}}

	add := func(p string) {
		if p == "" {
			return
		}
		key := searchRootKey(p)
		if _, dup := seen[key]; dup {
			return
		}
		seen[key] = struct{}{}
		roots = append(roots, p)
	}

	projRoot := ResolveProjectRoot()
	if projRoot != "" {
		add(projRoot)
	} else {
		// Default fallback: projects live under $CTASK_ROOT/projects/ when
		// no override is set. Explicit search root makes discovery work
		// from any shell.
		add(filepath.Join(taskRoot, "projects"))
	}
	return roots
}

// searchRootKey returns the dedup key for a root path: cleaned, and
// lower-cased on Windows for case-insensitive comparison.
func searchRootKey(p string) string {
	c := filepath.Clean(p)
	if runtime.GOOS == "windows" {
		return strings.ToLower(c)
	}
	return c
}

// samePath reports whether two absolute paths refer to the same directory
// on the current platform. Uses case-insensitive compare on Windows.
func samePath(a, b string) bool {
	ac := filepath.Clean(a)
	bc := filepath.Clean(b)
	if runtime.GOOS == "windows" {
		return strings.EqualFold(ac, bc)
	}
	return ac == bc
}

// EnvVars returns the environment variables to export into child sessions.
// taskType must be "task" or "project"; an empty value defaults to "task".
// launchDir is the workspace-relative project subdirectory for projects,
// or empty for tasks and pre-v0.5 projects.
func EnvVars(slug, mode, root, workspace, category, taskType, launchDir string) map[string]string {
	if taskType == "" {
		taskType = "task"
	}
	return map[string]string{
		"CTASK_TASK":       slug,
		"CTASK_MODE":       mode,
		"CTASK_ROOT":       root,
		"CTASK_WORKSPACE":  workspace,
		"CTASK_CATEGORY":   category,
		"CTASK_TYPE":       taskType,
		"CTASK_LAUNCH_DIR": launchDir,
	}
}

// defaultSeedDir returns the platform-default location for a seed directory leaf.
func defaultSeedDir(leaf string) string {
	if runtime.GOOS == "windows" {
		appData := os.Getenv("APPDATA")
		if appData == "" {
			home, _ := os.UserHomeDir()
			return filepath.Join(home, "AppData", "Roaming", "ctask", leaf)
		}
		return filepath.Join(appData, "ctask", leaf)
	}
	home, _ := os.UserHomeDir()
	return filepath.Join(home, ".config", "ctask", leaf)
}

// expandPath expands a leading ~/ and resolves to an absolute path when possible.
func expandPath(p string) string {
	if strings.HasPrefix(p, "~/") || p == "~" {
		home, _ := os.UserHomeDir()
		p = filepath.Join(home, p[1:])
	}
	abs, err := filepath.Abs(p)
	if err != nil {
		return p
	}
	return abs
}