// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package app

import (
	"errors"
	"fmt"

	"gitea.dev/tea/internal/services"
	"gitea.dev/tea/internal/settings"
	"gitea.dev/tea/internal/terminal"
	"github.com/spf13/cobra"
)

// preferences applies environment overrides to the stored preferences, matching config get --show-source.
func (a *application) preferences() (settings.Preferences, error) {
	snapshot, err := a.settings()
	if err != nil {
		return settings.Preferences{}, err
	}
	preferences, _, err := a.effectivePreferences(snapshot)
	return preferences, err
}

func (a *application) colorEnabled() bool {
	preferences, _ := a.preferences()
	return terminal.ColorEnabled(preferences.Color, a.deps.Streams.OutTTY, a.deps.Getenv)
}

// display describes stdout for tables and views under the color, hyperlinks and markdown preferences.
func (a *application) display() terminal.Display {
	preferences, _ := a.preferences()
	streams := a.deps.Streams
	return terminal.Display{
		TTY:      streams.OutTTY,
		Color:    terminal.ColorEnabled(preferences.Color, streams.OutTTY, a.deps.Getenv),
		Links:    terminal.HyperlinksEnabled(preferences.Hyperlinks, streams.OutTTY, a.deps.Getenv),
		Markdown: terminal.MarkdownEnabled(preferences.Markdown, streams.OutTTY),
		Width:    streams.Width,
		Now:      a.deps.Now(),
	}
}

// writeHuman pages human list and view text; --no-input does not disable paging.
func (a *application) writeHuman(cmd *cobra.Command, text string) error {
	preferences, _ := a.preferences()
	return terminal.WriteHuman(cmd.Context(), a.deps.Streams, preferences.Pager, a.deps.Pager, text)
}

// writeJSON writes v as JSON, filtered by --json fields and --jq.
func (a *application) writeJSON(cmd *cobra.Command, v any) error {
	pretty := a.deps.Streams.OutTTY
	return terminal.JSONOutput{Fields: a.options.json, Allowed: commandOutputFields(cmd), Query: a.options.jq, Pretty: pretty, Color: pretty && a.colorEnabled()}.Write(cmd.OutOrStdout(), v)
}

// listSpec describes how a list command shows its items to people.
type listSpec[T any] struct {
	Columns []terminal.Column
	Row     func(T) []terminal.Cell
	// Empty, such as "no open issues in alice/x", goes to stderr on a TTY when nothing is listed.
	Empty string
	// Context names the listed items, such as "open issues in alice/x", for the line that heads the
	// table on a TTY: "Showing 30 of 112 open issues in alice/x".
	Context string
}

// listPage places a page of items in the whole listing.
type listPage struct {
	// Number is the 1-based --page value.
	Number int
	// More reports later pages. Total is the size of the whole listing when Counted.
	More    bool
	Total   int
	Counted bool
}

// writeTable writes items as a JSON array, or as a table through the pager: on a TTY with a header,
// the spec's Context line, or its Empty message on stderr; piped as TSV with the next-page hint on stderr.
func writeTable[T any](a *application, cmd *cobra.Command, items []T, spec listSpec[T], page listPage) error {
	if a.options.json != "" {
		return a.writeJSON(cmd, items)
	}
	d := a.display()
	if len(items) == 0 {
		if !d.TTY || spec.Empty == "" {
			return nil
		}
		_, err := fmt.Fprintln(cmd.ErrOrStderr(), spec.Empty)
		return err
	}
	rows := make([][]terminal.Cell, len(items))
	for i, item := range items {
		rows[i] = spec.Row(item)
	}
	text := terminal.Table(spec.Columns, rows, d)
	if d.TTY && spec.Context != "" {
		return a.writeHuman(cmd, showing(len(items), page, spec.Context)+"\n\n"+text)
	}
	if err := a.writeHuman(cmd, text); err != nil {
		return err
	}
	return a.morePagesHint(cmd, page.More, page.Number)
}

// showing is the context line above a table: "Showing 30 of 112 open issues in alice/x · next: --page 2".
func showing(shown int, page listPage, what string) string {
	line := fmt.Sprintf("Showing %d", shown)
	switch {
	case page.Counted:
		line += fmt.Sprintf(" of %d", page.Total)
	case !page.More && page.Number <= 1:
		line += fmt.Sprintf(" of %d", shown)
	}
	line += " " + what
	if page.More {
		line += fmt.Sprintf(" · next: --page %d", page.Number+1)
	}
	return line
}

// writeView writes item as a JSON object, or as a view through the pager.
func writeView[T any](a *application, cmd *cobra.Command, item T, view func(T) terminal.View) error {
	if a.options.json != "" {
		return a.writeJSON(cmd, item)
	}
	return a.writeHuman(cmd, view(item).Render(a.display()))
}

// done reports a completed mutation on stderr, such as "✓ Closed issue alice/x#5 (Fix login)",
// when people read stdout: on a TTY and without --json.
func (a *application) done(cmd *cobra.Command, format string, args ...any) {
	if !a.deps.Streams.OutTTY || a.options.json != "" {
		return
	}
	a.feedback(cmd, "✓", "green", format, args...)
}

// warn reports on stderr a mutation that had nothing to do, such as "! Issue alice/x#5 (Fix login)
// is already closed", or a part of one that failed. Unlike done it is never silenced, so scripts
// and --json callers still learn about partial failures.
func (a *application) warn(cmd *cobra.Command, format string, args ...any) {
	a.feedback(cmd, "!", "yellow", format, args...)
}

func (a *application) feedback(cmd *cobra.Command, icon, color, format string, args ...any) {
	fmt.Fprintln(cmd.ErrOrStderr(), terminal.Colorize(color, icon, a.colorEnabled())+" "+terminal.SafeLine(fmt.Sprintf(format, args...)))
}

// jsonResult writes the result of a mutation when --json asks for it; people get a done line instead.
func (a *application) jsonResult(cmd *cobra.Command, item any) error {
	if a.options.json == "" {
		return nil
	}
	return a.writeJSON(cmd, item)
}

// created writes a created resource as JSON with --json, else its URL to stdout, so scripts can
// capture it: url=$(tea issue create …).
func (a *application) created(cmd *cobra.Command, item any, url string) error {
	if a.options.json != "" {
		return a.writeJSON(cmd, item)
	}
	_, err := fmt.Fprintln(cmd.OutOrStdout(), terminal.SafeLine(url))
	return err
}

// refLabel names an issue or pull request in feedback: "alice/x#5 (Fix login)".
func refLabel(repo string, number int64, title string) string {
	return fmt.Sprintf("%s#%d (%s)", repo, number, terminal.SafeLine(title))
}

// abortBatch stops a batch instead of recording an item failure.
type abortBatch struct{ error }

func (e abortBatch) Unwrap() error { return e.error }

// applyBatch applies run to each selection and continues past individual failures, which it
// returns prefixed with the selection's label. succeeded, when set, sees each result as it arrives.
func applyBatch[K, T any](cmd *cobra.Command, keys []K, label func(K) string, run func(K) (T, error), succeeded func(T)) ([]T, []error) {
	results := []T{}
	var failures []error
	for _, key := range keys {
		if err := cmd.Context().Err(); err != nil {
			failures = append(failures, err)
			break
		}
		item, err := run(key)
		if errors.As(err, new(abortBatch)) {
			failures = append(failures, err)
			break
		}
		if err != nil {
			failures = append(failures, fmt.Errorf("%s: %w", label(key), err))
			continue
		}
		results = append(results, item)
		if succeeded != nil {
			succeeded(item)
		}
	}
	return results, failures
}

// writeBatchJSON writes, with --json, an object for one selection (none if it failed), otherwise an array.
func writeBatchJSON[T any](a *application, cmd *cobra.Command, selections int, results []T) error {
	switch {
	case a.options.json == "":
		return nil
	case selections != 1:
		return a.writeJSON(cmd, results)
	case len(results) == 1:
		return a.writeJSON(cmd, results[0])
	}
	return nil
}

// batchDone applies a mutation to each selection like batch, reporting each success with a done
// line from report, such as "Closed issue alice/x#5 (Fix login)", and the results as JSON.
func batchDone[K, T any](a *application, cmd *cobra.Command, keys []K, label func(K) string, run func(K) (T, error), report func(T) string) error {
	results, failures := applyBatch(cmd, keys, label, run, func(item T) { a.done(cmd, "%s", report(item)) })
	return errors.Join(append(failures, writeBatchJSON(a, cmd, len(keys), results))...)
}

// stateColors colors issue, pull request and milestone states with the terminal's own palette.
var stateColors = map[string]string{"open": "green", "closed": "red", "merged": "magenta", "draft": "muted"}

// morePagesHint tells human readers on stderr that the listing continues past this page.
func (a *application) morePagesHint(cmd *cobra.Command, more bool, page int) error {
	if !more || a.options.json != "" {
		return nil
	}
	_, err := fmt.Fprintf(cmd.ErrOrStderr(), "more results available; use --page %d\n", page+1)
	return err
}

// yesNo renders a boolean cell.
func yesNo(value bool) string {
	if value {
		return "yes"
	}
	return "no"
}

// shortSHA abbreviates a commit ID to seven characters, as Gitea and Git show them.
func shortSHA(sha string) string {
	return sha[:min(len(sha), 7)]
}

// servicePage places a page of a service listing for writeTable.
func servicePage[T any](page services.Page[T], number int) listPage {
	return listPage{Number: number, More: page.More, Total: page.Total, Counted: page.Counted}
}