// TODO: error handling
// TODO: split combinedOutput and handle stderr differently
// TODO: reorder functions
package taskwarrior

import (
	"bytes"
	"encoding/json"
	"fmt"
	"log/slog"
	"os/exec"
	"regexp"
	"slices"
	"strings"
	"sync"
)

const (
	twBinary = "task"
)

var (
	nonStandardReports = map[string]struct{}{
		"burndown.daily":   {},
		"burndown.monthly": {},
		"burndown.weekly":  {},
		"calendar":         {},
		"colors":           {},
		"export":           {},
		"ghistory.annual":  {},
		"ghistory.monthly": {},
		"history.annual":   {},
		"history.monthly":  {},
		"information":      {},
		"summary":          {},
		"timesheet":        {},
	}

	virtualTags = map[string]struct{}{
		"ACTIVE":    {},
		"ANNOTATED": {},
		"BLOCKED":   {},
		"BLOCKING":  {},
		"CHILD":     {},
		"COMPLETED": {},
		"DELETED":   {},
		"DUE":       {},
		"DUETODAY":  {},
		"INSTANCE":  {},
		"LATEST":    {},
		"MONTH":     {},
		"ORPHAN":    {},
		"OVERDUE":   {},
		"PARENT":    {},
		"PENDING":   {},
		"PRIORITY":  {},
		"PROJECT":   {},
		"QUARTER":   {},
		"READY":     {},
		"SCHEDULED": {},
		"TAGGED":    {},
		"TEMPLATE":  {},
		"TODAY":     {},
		"TOMORROW":  {},
		"UDA":       {},
		"UNBLOCKED": {},
		"UNTIL":     {},
		"WAITING":   {},
		"WEEK":      {},
		"YEAR":      {},
		"YESTERDAY": {},
	}
)

type TaskWarrior interface {
	GetConfig() *TWConfig

	GetActiveContext() *Context
	GetContext(context string) *Context
	GetContexts() Contexts
	SetContext(context *Context) error

	GetProjects() []string

	GetPriorities() []string

	GetTags() []string

	GetReport(report string) *Report
	GetReports() Reports

	GetTasks(report *Report, filter ...string) Tasks
	AddTask(task *Task) error
	ImportTask(task *Task)
	SetTaskDone(task *Task)
	StartTask(task *Task)
	StopTask(task *Task)

	Undo()
}

type TaskSquire struct {
	configLocation string
	defaultArgs    []string
	config         *TWConfig
	reports        Reports
	contexts       Contexts

	mutex sync.Mutex
}

func NewTaskSquire(configLocation string) *TaskSquire {
	if _, err := exec.LookPath(twBinary); err != nil {
		slog.Error("Taskwarrior not found")
		return nil
	}
	defaultArgs := []string{fmt.Sprintf("rc=%s", configLocation), "rc.verbose=nothing", "rc.dependency.confirmation=no", "rc.recurrence.confirmation=no", "rc.confirmation=no", "rc.json.array=1"}

	ts := &TaskSquire{
		configLocation: configLocation,
		defaultArgs:    defaultArgs,
		mutex:          sync.Mutex{},
	}
	ts.config = ts.extractConfig()
	ts.reports = ts.extractReports()
	ts.contexts = ts.extractContexts()

	return ts
}

func (ts *TaskSquire) GetConfig() *TWConfig {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	return ts.config
}

func (ts *TaskSquire) GetTasks(report *Report, filter ...string) Tasks {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	args := ts.defaultArgs

	if report.Context {
		for _, context := range ts.contexts {
			if context.Active && context.Name != "none" {
				args = append(args, context.ReadFilter)
				break
			}
		}
	}

	if filter != nil {
		args = append(args, filter...)
	}

	cmd := exec.Command(twBinary, append(args, []string{"export", report.Name}...)...)
	output, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed getting report:", err)
		return nil
	}

	tasks := make(Tasks, 0)
	err = json.Unmarshal(output, &tasks)
	if err != nil {
		slog.Error("Failed unmarshalling tasks:", err)
		return nil
	}

	for _, task := range tasks {
		if task.Depends != nil && len(task.Depends) > 0 {
			ids := make([]string, len(task.Depends))
			for i, dependUuid := range task.Depends {
				ids[i] = ts.getIds([]string{fmt.Sprintf("uuid:%s", dependUuid)})
			}

			task.DependsIds = strings.Join(ids, " ")
		}
	}

	return tasks
}

func (ts *TaskSquire) getIds(filter []string) string {
	cmd := exec.Command(twBinary, append(append(ts.defaultArgs, filter...), "_ids")...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed getting field:", err)
		return ""
	}

	return strings.TrimSpace(string(out))
}

func (ts *TaskSquire) GetContext(context string) *Context {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	if context == "" {
		context = "none"
	}

	if context, ok := ts.contexts[context]; ok {
		return context
	} else {
		slog.Error(fmt.Sprintf("Context not found: %s", context.Name))
		return nil
	}
}

func (ts *TaskSquire) GetActiveContext() *Context {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	for _, context := range ts.contexts {
		if context.Active {
			return context
		}
	}

	return ts.contexts["none"]
}

func (ts *TaskSquire) GetContexts() Contexts {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	return ts.contexts
}

func (ts *TaskSquire) GetProjects() []string {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"_projects"}...)...)

	output, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed getting projects:", err)
		return nil
	}

	projects := make([]string, 0)
	for _, project := range strings.Split(string(output), "\n") {
		if project != "" {
			projects = append(projects, project)
		}
	}

	slices.Sort(projects)

	return projects
}

func (ts *TaskSquire) GetPriorities() []string {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	priorities := make([]string, 0)
	for _, priority := range strings.Split(ts.config.Get("uda.priority.values"), ",") {
		if priority != "" {
			priorities = append(priorities, priority)
		}
	}

	return priorities
}

func (ts *TaskSquire) GetTags() []string {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"_tags"}...)...)

	output, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed getting tags:", err)
		return nil
	}

	tags := make([]string, 0)

	for _, tag := range strings.Split(string(output), "\n") {
		if _, ok := virtualTags[tag]; !ok && tag != "" {
			tags = append(tags, tag)
		}
	}

	slices.Sort(tags)

	return tags
}

func (ts *TaskSquire) GetReport(report string) *Report {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	return ts.reports[report]
}

func (ts *TaskSquire) GetReports() Reports {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	return ts.reports
}

func (ts *TaskSquire) SetContext(context *Context) error {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	if context.Name == "none" && ts.contexts["none"].Active {
		return nil
	}

	cmd := exec.Command(twBinary, []string{"context", context.Name}...)
	if err := cmd.Run(); err != nil {
		slog.Error("Failed setting context:", err)
		return err
	}

	// TODO: optimize this; there should be no need to re-extract everything
	ts.config = ts.extractConfig()
	ts.contexts = ts.extractContexts()

	return nil
}

func (ts *TaskSquire) AddTask(task *Task) error {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	addArgs := []string{"add"}

	if task.Description == "" {
		slog.Error("Task description is required")
		return nil
	} else {
		addArgs = append(addArgs, task.Description)
	}
	if task.Priority != "" && task.Priority != "(none)" {
		addArgs = append(addArgs, fmt.Sprintf("priority:%s", task.Priority))
	}
	if task.Project != "" && task.Project != "(none)" {
		addArgs = append(addArgs, fmt.Sprintf("project:%s", task.Project))
	}
	if task.Tags != nil {
		for _, tag := range task.Tags {
			addArgs = append(addArgs, fmt.Sprintf("+%s", tag))
		}
	}
	if task.Due != "" {
		addArgs = append(addArgs, fmt.Sprintf("due:%s", task.Due))
	}

	cmd := exec.Command(twBinary, append(ts.defaultArgs, addArgs...)...)
	err := cmd.Run()
	if err != nil {
		slog.Error("Failed adding task:", err)
	}

	// TODO remove error?
	return nil
}

// TODO error handling
func (ts *TaskSquire) ImportTask(task *Task) {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	tasks, err := json.Marshal(Tasks{task})

	if err != nil {
		slog.Error("Failed marshalling task:", err)
	}

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"import", "-"}...)...)
	cmd.Stdin = bytes.NewBuffer(tasks)
	out, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed modifying task:", err, string(out))
	}
}

func (ts *TaskSquire) SetTaskDone(task *Task) {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"done", task.Uuid}...)...)
	err := cmd.Run()
	if err != nil {
		slog.Error("Failed setting task done:", err)
	}
}

func (ts *TaskSquire) Undo() {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"undo"}...)...)
	err := cmd.Run()
	if err != nil {
		slog.Error("Failed undoing task:", err)
	}
}

func (ts *TaskSquire) StartTask(task *Task) {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"start", task.Uuid}...)...)
	err := cmd.Run()
	if err != nil {
		slog.Error("Failed starting task:", err)
	}
}

func (ts *TaskSquire) StopTask(task *Task) {
	ts.mutex.Lock()
	defer ts.mutex.Unlock()

	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"stop", task.Uuid}...)...)
	err := cmd.Run()
	if err != nil {
		slog.Error("Failed stopping task:", err)
	}
}

func (ts *TaskSquire) extractConfig() *TWConfig {
	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"_show"}...)...)
	output, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed getting config:", err)
		return nil
	}

	return NewConfig(strings.Split(string(output), "\n"))
}

func (ts *TaskSquire) extractReports() Reports {
	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"_config"}...)...)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return nil
	}

	availableReports := extractReports(string(output))

	reports := make(Reports)

	for _, report := range availableReports {
		if _, ok := nonStandardReports[report]; ok {
			continue
		}
		reports[report] = &Report{
			Name:        report,
			Description: ts.config.Get(fmt.Sprintf("report.%s.description", report)),
			Labels:      strings.Split(ts.config.Get(fmt.Sprintf("report.%s.labels", report)), ","),
			Filter:      ts.config.Get(fmt.Sprintf("report.%s.filter", report)),
			Sort:        ts.config.Get(fmt.Sprintf("report.%s.sort", report)),
			Columns:     strings.Split(ts.config.Get(fmt.Sprintf("report.%s.columns", report)), ","),
			Context:     ts.config.Get(fmt.Sprintf("report.%s.context", report)) == "1",
		}
	}

	return reports
}

func extractReports(config string) []string {
	re := regexp.MustCompile(`report\.([^.]+)\.[^.]+`)
	matches := re.FindAllStringSubmatch(config, -1)
	uniques := make(map[string]struct{})
	for _, match := range matches {
		uniques[match[1]] = struct{}{}
	}

	var reports []string
	for part := range uniques {
		reports = append(reports, part)
	}

	slices.Sort(reports)
	return reports
}

func (ts *TaskSquire) extractContexts() Contexts {
	cmd := exec.Command(twBinary, append(ts.defaultArgs, []string{"_context"}...)...)

	output, err := cmd.CombinedOutput()
	if err != nil {
		slog.Error("Failed getting contexts:", err)
		return nil
	}

	activeContext := ts.config.Get("context")
	if activeContext == "" {
		activeContext = "none"
	}

	contexts := make(Contexts)
	contexts["none"] = &Context{
		Name:        "none",
		Active:      activeContext == "none",
		ReadFilter:  "",
		WriteFilter: "",
	}
	for _, context := range strings.Split(string(output), "\n") {
		if context == "" {
			continue
		}
		contexts[context] = &Context{
			Name:        context,
			Active:      activeContext == context,
			ReadFilter:  ts.config.Get(fmt.Sprintf("context.%s.read", context)),
			WriteFilter: ts.config.Get(fmt.Sprintf("context.%s.write", context)),
		}
	}

	return contexts
}