package handler

import (
	"context"
	"html"
	"net/url"
	"net/http"
	"strings"

	"github.com/LazyBachelor/LazyPM/internal/models"
	"github.com/LazyBachelor/LazyPM/pkg/web/routes"
	"github.com/go-chi/chi/v5"
)

const issueKey = "issue"
const commentsKey = "comments"

type IssueForm struct {
	Title       string           `form:"title" validate:"required,max=255"`
	Description string           `form:"description" validate:"max=2000"`
	Status      models.Status    `form:"status" validate:"required,oneof=open in_progress blocked ready_to_sprint closed"`
	IssueType   models.IssueType `form:"issue_type" validate:"required,oneof=task bug feature chore"`
	Priority    int              `form:"priority" validate:"gte=0,lte=4"`
}

type UpdateIssueForm struct {
	Title       *string           `form:"title" validate:"omitempty,max=255"`
	Description *string           `form:"description" validate:"omitempty,max=2000"`
	Status      *models.Status    `form:"status" validate:"omitempty,oneof=open in_progress blocked ready_to_sprint closed"`
	CloseReason *string           `form:"close_reason" validate:"omitempty,max=2000"`
	IssueType   *models.IssueType `form:"issue_type" validate:"omitempty,oneof=task bug feature chore"`
	Priority    *int              `form:"priority" validate:"omitempty,gte=0,lte=4"`
}

func CreateIssue(w http.ResponseWriter, r *http.Request) {
	app := App(r)
	hx := HTMX(r)

	form, err := ParseForm[IssueForm](r)
	if err != nil {
		http.Error(w, "Failed to parse form", http.StatusBadRequest)
		return
	}

	if err := ValidateForm(form); err != nil {
		if hx.IsHxRequest() {
			hx.WriteString("<div class=\"alert alert-error\">Please fix the form errors: " + err.Error() + "</div>")
		} else {
			http.Error(w, "Validation error: "+err.Error(), http.StatusUnprocessableEntity)
		}
		return
	}

	issue := form.toIssue()
	issue.CreatedBy = "Me"
	if err := app.Issues.CreateIssue(r.Context(), issue, "Me"); err != nil {
		http.Error(w, "Failed to create issue: "+err.Error(), http.StatusInternalServerError)
		return
	}

	if hx.IsHxRequest() {
		// Check if 'from' parameter says board view
		from := r.URL.Query().Get("from")
		referer := r.Header.Get("Referer")
		boardView := from == "board" || strings.Contains(referer, "board=true")
		
		if boardView {
			w.Header().Set("HX-Redirect", "/?board=true")
		} else {
			w.Header().Set("HX-Redirect", "/?selected-issue="+issue.ID)
		}
		return
	}

	w.Header().Set("Content-Type", "application/json")
	hx.WriteJSON(issue)
}

func ListIssues(w http.ResponseWriter, r *http.Request) {
	app := App(r)
	hx := HTMX(r)

	issues, err := app.Issues.SearchIssues(r.Context(), "", models.IssueFilter{})
	if err != nil {
		http.Error(w, "Failed to retrieve issues", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	hx.WriteJSON(issues)
}

func IssueCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		app := App(r)

		id := chi.URLParam(r, "id")
		issue, err := app.Issues.GetIssue(r.Context(), id)
		if err != nil {
			http.Error(w, "Error getting issue: "+err.Error(), http.StatusNotFound)
			return
		}
		if issue == nil {
			http.Error(w, "Issue not found", http.StatusNotFound)
			return
		}

		comments, err := app.Issues.GetIssueComments(r.Context(), issue.ID)
		if err != nil {
			http.Error(w, "Error getting comments: "+err.Error(), http.StatusInternalServerError)
			return
		}

		ctx := context.WithValue(r.Context(), issueKey, issue)
		ctx = context.WithValue(ctx, commentsKey, comments)
		next.ServeHTTP(w, r.WithContext(ctx))
	})

}

func GetIssue(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	comments := r.Context().Value(commentsKey).([]*models.Comment)
	hx := HTMX(r)

	from := r.URL.Query().Get("from")
	detailProps := routes.IssueDetailProps{
		Issue:    issue,
		Comments: comments,
		From:     from,
	}

	if !hx.IsHxRequest() && strings.Contains(r.Header.Get("Accept"), "text/html") {
		routes.IssueDetail(detailProps).Render(r.Context(), w)
		return
	}

	if hx.IsHxRequest() {
		routes.IssueDetailContent(detailProps).Render(r.Context(), w)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	hx.WriteJSON(issue)
}

func UpdateIssue(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	app := App(r)
	hx := HTMX(r)

	form, err := ParseForm[UpdateIssueForm](r)
	if err != nil {
		http.Error(w, "Failed to parse form", http.StatusBadRequest)
		return
	}

	if err := ValidateForm(form); err != nil {
		if hx.IsHxRequest() {
			hx.WriteString("<div>Please fix the form errors</div>")
		} else {
			http.Error(w, "Validation error: "+err.Error(), http.StatusUnprocessableEntity)
		}
		return
	}

	changes := form.toChanges()

	if err := app.Issues.UpdateIssue(r.Context(), issue.ID, changes, ""); err != nil {
		http.Error(w, "Failed to update issue", http.StatusInternalServerError)
		return
	}

	issue, err = app.Issues.GetIssue(r.Context(), issue.ID)
	if err != nil {
		http.Error(w, "Failed to retrieve updated issue", http.StatusInternalServerError)
		return
	}

	if hx.IsHxRequest() {
		// Check if 'from' parameter says board view
		from := r.URL.Query().Get("from")
		referer := r.Header.Get("Referer")
		boardView := from == "board" || strings.Contains(referer, "board=true")
		
		if boardView {
			w.Header().Set("HX-Redirect", "/?board=true")
		} else {
			w.Header().Set("HX-Redirect", "/?selected-issue="+issue.ID)
		}
		return
	}

	w.Header().Set("Content-Type", "application/json")
	hx.WriteJSON(issue)
}

func UpdateAssignee(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	assignee := r.FormValue("assignee")

	if err := App(r).Issues.UpdateIssue(r.Context(), issue.ID, map[string]any{"assignee": assignee}, ""); err != nil {
		http.Error(w, "Failed to update assignee", http.StatusInternalServerError)
		return
	}

	issue, err := App(r).Issues.GetIssue(r.Context(), issue.ID)
	if err != nil {
		http.Error(w, "Failed to retrieve updated issue", http.StatusInternalServerError)
		return
	}

	if HTMX(r).IsHxRequest() {
		// Check if we're in board view
		referer := r.Header.Get("Referer")
		boardView := strings.Contains(referer, "board=true")
		
		if boardView {
			w.Header().Set("HX-Redirect", "/?board=true&selected-issue="+issue.ID)
		} else {
			w.Header().Set("HX-Redirect", "/?selected-issue="+issue.ID)
		}
		return
	}

	w.Header().Set("Content-Type", "application/json")
	HTMX(r).WriteJSON(issue)
}

// Returns a simple HTML fragment listing dependencies for an issue
func ListDependencies(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	app := App(r)

	deps, err := app.Issues.GetDependencies(r.Context(), issue.ID)
	if err != nil {
		http.Error(w, "Failed to load dependencies", http.StatusInternalServerError)
		return
	}

	containerID := r.URL.Query().Get("container_id")
	if containerID == "" {
		containerID = "dependencies-list"
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")

	if len(deps) == 0 {
		_, _ = w.Write([]byte(`<div id="` + html.EscapeString(containerID) + `" class="text-sm text-base-content/60">No dependencies.</div>`))
		return
	}

	builder := strings.Builder{}
	builder.WriteString(`<div id="` + html.EscapeString(containerID) + `" class="space-y-1">`)
	for _, d := range deps {
		if d == nil {
			continue
		}
		builder.WriteString(`<div class="flex items-center justify-between gap-2 border rounded px-2 py-1 text-sm">`)
		builder.WriteString(`<span class="truncate">`)
		builder.WriteString(`<span class="font-mono">`)
		builder.WriteString(html.EscapeString(d.ID))
		builder.WriteString(`</span>`)
		if d.Title != "" {
			builder.WriteString(`<span class="opacity-70"> — `)
			builder.WriteString(html.EscapeString(d.Title))
			builder.WriteString(`</span>`)
		}
		builder.WriteString(`</span>`)
		builder.WriteString(`<button class="btn btn-xs btn-ghost text-error" `)
		builder.WriteString(`hx-delete="/issues/`)
		builder.WriteString(html.EscapeString(issue.ID))
		builder.WriteString(`/dependencies?container_id=` + url.QueryEscape(containerID) + `" hx-target="#` + html.EscapeString(containerID) + `" hx-swap="outerHTML" `)
		builder.WriteString(`hx-vals='{"depends_on_id":"`)
		builder.WriteString(html.EscapeString(d.ID))
		builder.WriteString(`"}'>Remove</button>`)
		builder.WriteString(`</div>`)
	}
	builder.WriteString(`</div>`)

	_, _ = w.Write([]byte(builder.String()))
}

// Adding a new dependency (issue depends on depends_on_id)
func AddDependencyHandler(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	app := App(r)

	if err := r.ParseForm(); err != nil {
		http.Error(w, "Invalid form data", http.StatusBadRequest)
		return
	}

	dependsOnID := r.FormValue("depends_on_id")
	if dependsOnID == "" {
		http.Error(w, "Dependency ID is required", http.StatusBadRequest)
		return
	}

	depType := models.DepBlocks
	dep := &models.Dependency{
		IssueID:     issue.ID,
		DependsOnID: dependsOnID,
		Type:        depType,
	}

	if err := app.Issues.AddDependency(r.Context(), dep, "web"); err != nil {
		http.Error(w, "Failed to add dependency: "+err.Error(), http.StatusInternalServerError)
		return
	}

	w.Header().Set("HX-Trigger", "dependencies-updated")

	// Re-render the list so HTMX can swap it in
	ListDependencies(w, r)
}

// Removing an existing dependency
func RemoveDependencyHandler(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	app := App(r)

	dependsOnID := r.FormValue("depends_on_id")
	if dependsOnID == "" {
		dependsOnID = r.URL.Query().Get("depends_on_id")
	}
	if dependsOnID == "" {
		http.Error(w, "Dependency ID is required", http.StatusBadRequest)
		return
	}

	if err := app.Issues.RemoveDependency(r.Context(), issue.ID, dependsOnID, "web"); err != nil {
		http.Error(w, "Failed to remove dependency: "+err.Error(), http.StatusInternalServerError)
		return
	}

	w.Header().Set("HX-Trigger", "dependencies-updated")

	// Re-render the list so HTMX can swap it in
	ListDependencies(w, r)
}

// DependencyOptions renders <option> tags for dependency selection in the edit modal.
// we exclude:
// - the current issue
// - issues this issue already depends on
// - issues that already depend on this issue (dependents)
func DependencyOptions(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)
	app := App(r)

	all, err := app.Issues.SearchIssues(r.Context(), "", models.IssueFilter{})
	if err != nil {
		http.Error(w, "Failed to load issues", http.StatusInternalServerError)
		return
	}

	deps, err := app.Issues.GetDependencies(r.Context(), issue.ID)
	if err != nil {
		http.Error(w, "Failed to load dependencies", http.StatusInternalServerError)
		return
	}

	dependents, err := app.Issues.GetDependents(r.Context(), issue.ID)
	if err != nil {
		http.Error(w, "Failed to load dependents", http.StatusInternalServerError)
		return
	}

	exclude := map[string]struct{}{issue.ID: {}}
	for _, d := range deps {
		if d != nil {
			exclude[d.ID] = struct{}{}
		}
	}
	for _, d := range dependents {
		if d != nil {
			exclude[d.ID] = struct{}{}
		}
	}

	var b strings.Builder
	b.WriteString(`<option value="">Select issue…</option>`)
	for _, iss := range all {
		if iss == nil {
			continue
		}
		if _, skip := exclude[iss.ID]; skip {
			continue
		}
		// Show "ID — Title" for quick scanning
		b.WriteString(`<option value="`)
		b.WriteString(html.EscapeString(iss.ID))
		b.WriteString(`">`)
		b.WriteString(html.EscapeString(iss.ID))
		if iss.Title != "" {
			b.WriteString(` — `)
			b.WriteString(html.EscapeString(iss.Title))
		}
		b.WriteString(`</option>`)
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_, _ = w.Write([]byte(b.String()))
}

func DeleteIssue(w http.ResponseWriter, r *http.Request) {
	issue := r.Context().Value(issueKey).(*models.Issue)

	if err := App(r).Issues.DeleteIssue(r.Context(), issue.ID); err != nil {
		http.Error(w, "Failed to delete issue", http.StatusInternalServerError)
		return
	}

	if HTMX(r).IsHxRequest() {
		// Check if 'from' parameter indicates board view
		from := r.URL.Query().Get("from")
		referer := r.Header.Get("Referer")
		boardView := from == "board" || strings.Contains(referer, "board=true")
		
		if boardView {
			w.Header().Set("HX-Redirect", "/?board=true")
		} else {
			w.Header().Set("HX-Redirect", "/")
		}
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

func CloseIssue(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	issueVal := r.Context().Value(issueKey)
	issue, ok := issueVal.(*models.Issue)
	if !ok || issue == nil {
		http.Error(w, "Issue not found in context", http.StatusInternalServerError)
		return
	}

	closeReason := r.FormValue("close_reason")

	if closeReason == "" {
		if HTMX(r).IsHxRequest() {
			w.WriteHeader(http.StatusBadRequest)
			HTMX(r).WriteString("<div class=\"alert alert-error\">Closing reason is required</div>")
		} else {
			http.Error(w, "Closing reason is required", http.StatusBadRequest)
		}
		return
	}

	if err := App(r).Issues.CloseIssue(r.Context(), issue.ID, closeReason, "web", ""); err != nil {
		if HTMX(r).IsHxRequest() {
			w.WriteHeader(http.StatusInternalServerError)
			HTMX(r).WriteString("<div class=\"alert alert-error\">Failed to close issue: " + html.EscapeString(err.Error()) + "</div>")
		} else {
			http.Error(w, "Failed to close issue: "+err.Error(), http.StatusInternalServerError)
		}
		return
	}

	if HTMX(r).IsHxRequest() {
		w.Header().Set("HX-Refresh", "true")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

func (f *IssueForm) toIssue() *models.Issue {
	return &models.Issue{
		Title:       f.Title,
		Description: f.Description,
		Status:      f.Status,
		IssueType:   f.IssueType,
		Priority:    f.Priority,
	}
}

func (f *UpdateIssueForm) toChanges() map[string]any {
	changes := make(map[string]any)
	if f.Title != nil {
		changes["title"] = *f.Title
	}
	if f.Description != nil {
		changes["description"] = *f.Description
	}
	if f.Status != nil {
		changes["status"] = *f.Status
	}
	if f.CloseReason != nil {
		changes["close_reason"] = *f.CloseReason
	}
	if f.IssueType != nil {
		changes["issue_type"] = *f.IssueType
	}
	if f.Priority != nil {
		changes["priority"] = *f.Priority
	}
	return changes
}