// Copyright 2016 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package gitgraph

import (
	"bufio"
	"bytes"
	"context"
	"strings"

	"gitea.dev/modules/git"
	"gitea.dev/modules/git/gitcmd"
	"gitea.dev/modules/setting"
)

const gitLogGraphFormatSep = "^" // disallowed char in git ref names

// GetCommitGraph return a list of commit (GraphItems) from all branches
func GetCommitGraph(ctx context.Context, gitRepo *git.Repository, page, maxAllowedColors int, hidePRRefs bool, refs, files []string) (*Graph, error) {
	format := "DATA:" + strings.Join([]string{
		"%D",  // ref names without the " (", ")" wrapping.
		"%H",  // commit hash
		"%ad", // author date (format respects --date= option)
		"%h",  // abbreviated commit hash
		"%s",  // subject
	}, gitLogGraphFormatSep)

	page = max(page, 1)
	graphCmd := gitcmd.NewCommand("log", "--graph", "--date-order", "--decorate=full")

	if hidePRRefs {
		graphCmd.AddArguments("--exclude=" + git.PullPrefix + "*")
	}

	if len(refs) == 0 {
		graphCmd.AddArguments("--tags", "--branches")
	}

	graphCmd.AddArguments("--find-copies", "--find-renames", "--date=iso-strict").
		AddOptionFormat("-n %d", setting.UI.GraphMaxCommitNum*page).
		AddOptionFormat("--pretty=format:%s", format)

	if len(refs) > 0 {
		graphCmd.AddDynamicArguments(refs...)
	}
	if len(files) > 0 {
		graphCmd.AddDashesAndList(files...)
	}
	graph := NewGraph()

	commitsToSkip := setting.UI.GraphMaxCommitNum * (page - 1)

	stdoutReader, stdoutReaderClose := graphCmd.MakeStdoutPipe()
	defer stdoutReaderClose()
	if err := graphCmd.
		WithRepo(gitRepo).
		WithPipelineFunc(func(ctx gitcmd.Context) error {
			scanner := bufio.NewScanner(stdoutReader)
			parser := &Parser{}
			parser.firstInUse = -1
			parser.maxAllowedColors = maxAllowedColors
			if maxAllowedColors > 0 {
				parser.availableColors = make([]int, maxAllowedColors)
				for i := range parser.availableColors {
					parser.availableColors[i] = i + 1
				}
			} else {
				parser.availableColors = []int{1, 2}
			}
			for commitsToSkip > 0 && scanner.Scan() {
				line := scanner.Bytes()
				dataIdx := bytes.Index(line, []byte("DATA:"))
				if dataIdx < 0 {
					dataIdx = len(line)
				}
				starIdx := bytes.IndexByte(line, '*')
				if starIdx >= 0 && starIdx < dataIdx {
					commitsToSkip--
				}
				parser.ParseGlyphs(line[:dataIdx])
			}

			row := 0

			// Skip initial non-commit lines
			for scanner.Scan() {
				line := scanner.Bytes()
				if bytes.IndexByte(line, '*') >= 0 {
					if err := parser.AddLineToGraph(graph, row, line); err != nil {
						return ctx.CancelPipeline(err)
					}
					break
				}
				parser.ParseGlyphs(line)
			}

			for scanner.Scan() {
				row++
				line := scanner.Bytes()
				if err := parser.AddLineToGraph(graph, row, line); err != nil {
					return ctx.CancelPipeline(err)
				}
			}
			return scanner.Err()
		}).
		RunWithStderr(ctx); err != nil {
		return graph, err
	}
	return graph, nil
}