package mirclike

import (
	"errors"
	"strconv"
	"strings"
	"time"

	"git.aiterp.net/rpdata/api/models"
)

// ErrNotPost is returned by parsePost if the line is empty or not a post.
var ErrNotPost = errors.New("not a post")

// ParsePost parses a post from a mirc-like line. If the previous post is included (it can be empty), it will be used
// to determine whether midnight has passed.
func ParsePost(line string, date time.Time, prev models.Post) (models.Post, error) {
	// Do basic validation
	line = strings.Trim(line, "  \t\n\r")
	if len(line) == 0 || !strings.HasPrefix(line, "[") {
		return models.Post{}, ErrNotPost
	}

	// Parse timestamp
	tsEndIndex := strings.IndexByte(line, ']')
	if tsEndIndex == -1 || len(line) < tsEndIndex+5 {
		return models.Post{}, ErrNotPost
	}
	tsStr := line[1:tsEndIndex]
	tsSplit := strings.Split(tsStr, ":")
	tsUnits := make([]int, len(tsSplit))
	if len(tsSplit) < 2 {
		return models.Post{}, ErrNotPost
	}
	for i := range tsSplit {
		n, err := strconv.Atoi(tsSplit[i])
		if err != nil {
			return models.Post{}, ErrNotPost
		}

		tsUnits[i] = n
	}
	if len(tsUnits) == 2 {
		tsUnits = append(tsUnits, 0)
	}

	// Determine timestamp from parsed data and previous post.
	ts := time.Date(date.Year(), date.Month(), date.Day(), tsUnits[0], tsUnits[1], tsUnits[2], 0, date.Location())
	if !prev.Time.IsZero() && prev.Time.Sub(ts) > 30*time.Minute {
		ts = time.Date(prev.Time.Year(), prev.Time.Month(), prev.Time.Day()+1, tsUnits[0], tsUnits[1], tsUnits[2], 0, date.Location())
	}

	if line[tsEndIndex+2] == '*' {
		split := strings.SplitN(line[tsEndIndex+4:], " ", 2)
		if len(split) == 1 {
			return models.Post{}, ErrNotPost
		}

		post := models.Post{
			ID:       "UNASSIGNED",
			LogID:    "UNASSIGNED",
			Time:     ts,
			Kind:     "action",
			Nick:     strings.TrimLeft(split[0], "+@!~"),
			Text:     split[1],
			Position: prev.Position + 1,
		}

		if post.Nick[0] == '=' {
			post.Kind = "scene"
		}

		return post, nil
	} else if line[tsEndIndex+2] == '<' {
		split := strings.SplitN(line[tsEndIndex+2:], " ", 2)
		if len(split) == 1 {
			return models.Post{}, ErrNotPost
		}

		post := models.Post{
			ID:       "UNASSIGNED",
			LogID:    "UNASSIGNED",
			Time:     ts,
			Kind:     "text",
			Nick:     strings.TrimLeft(split[0][1:len(split[0])-1], "+@!~"),
			Text:     split[1],
			Position: prev.Position + 1,
		}

		if post.Nick[0] == '=' {
			post.Kind = "scene"
		}

		return post, nil
	} else {
		return models.Post{}, ErrNotPost
	}
}