<script lang="ts">
import {defineComponent} from 'vue';
import {SvgIcon} from '../svg.ts';
import {GET} from '../modules/fetch.ts';
import {generateElemId} from '../utils/dom.ts';

type Commit = {
  id: string,
  hovered: boolean,
  selected: boolean,
  summary: string,
  committer_or_author_name: string,
  time: string,
  short_sha: string,
}

type CommitListResult = {
  commits: Array<Commit>,
  last_review_commit_sha: string,
  locale: Record<string, string>,
}

export default defineComponent({
  components: {SvgIcon},
  data: () => {
    const el = document.querySelector('#diff-commit-select');
    return {
      menuVisible: false,
      isLoading: false,
      queryParams: el.getAttribute('data-queryparams'),
      issueLink: el.getAttribute('data-issuelink'),
      locale: {
        filter_changes_by_commit: el.getAttribute('data-filter_changes_by_commit'),
      } as Record<string, string>,
      mergeBase: el.getAttribute('data-merge-base'),
      commits: [] as Array<Commit>,
      hoverActivated: false,
      lastReviewCommitSha: '',
      uniqueIdMenu: generateElemId('diff-commit-selector-menu-'),
      uniqueIdShowAll: generateElemId('diff-commit-selector-show-all-'),
    };
  },
  computed: {
    commitsSinceLastReview() {
      if (this.lastReviewCommitSha) {
        return this.commits.length - this.commits.findIndex((x) => x.id === this.lastReviewCommitSha) - 1;
      }
      return 0;
    },
  },
  mounted() {
    document.body.addEventListener('click', this.onBodyClick);
    this.$el.addEventListener('keydown', this.onKeyDown);
    this.$el.addEventListener('keyup', this.onKeyUp);
  },
  unmounted() {
    document.body.removeEventListener('click', this.onBodyClick);
    this.$el.removeEventListener('keydown', this.onKeyDown);
    this.$el.removeEventListener('keyup', this.onKeyUp);
  },
  methods: {
    onBodyClick(event: MouseEvent) {
      // close this menu on click outside of this element when the dropdown is currently visible opened
      if (this.$el.contains(event.target)) return;
      if (this.menuVisible) {
        this.toggleMenu();
      }
    },
    onKeyDown(event: KeyboardEvent) {
      if (!this.menuVisible) return;
      const item = document.activeElement as HTMLElement;
      if (!this.$el.contains(item)) return;
      switch (event.key) {
        case 'ArrowDown': // select next element
          event.preventDefault();
          this.focusElem(item.nextElementSibling as HTMLElement, item);
          break;
        case 'ArrowUp': // select previous element
          event.preventDefault();
          this.focusElem(item.previousElementSibling as HTMLElement, item);
          break;
        case 'Escape': // close menu
          event.preventDefault();
          item.tabIndex = -1;
          this.toggleMenu();
          break;
      }
      if (event.key === 'ArrowDown' || event.key === 'ArrowUp') {
        const item = document.activeElement; // try to highlight the selected commits
        const commitIdx = item?.matches('.item') ? item.getAttribute('data-commit-idx') : null;
        if (commitIdx) this.highlight(this.commits[Number(commitIdx)]);
      }
    },
    onKeyUp(event: KeyboardEvent) {
      if (!this.menuVisible) return;
      const item = document.activeElement;
      if (!this.$el.contains(item)) return;
      if (event.key === 'Shift' && this.hoverActivated) {
        // shift is not pressed anymore -> deactivate hovering and reset hovered and selected
        this.hoverActivated = false;
        for (const commit of this.commits) {
          commit.hovered = false;
          commit.selected = false;
        }
      }
    },
    highlight(commit: Commit) {
      if (!this.hoverActivated) return;
      const indexSelected = this.commits.findIndex((x) => x.selected);
      const indexCurrentElem = this.commits.findIndex((x) => x.id === commit.id);
      for (const [idx, commit] of this.commits.entries()) {
        commit.hovered = Math.min(indexSelected, indexCurrentElem) <= idx && idx <= Math.max(indexSelected, indexCurrentElem);
      }
    },
    /** Focus given element */
    focusElem(elem: HTMLElement, prevElem: HTMLElement) {
      if (elem) {
        elem.tabIndex = 0;
        if (prevElem) prevElem.tabIndex = -1;
        elem.focus();
      }
    },
    /** Opens our menu, loads commits before opening */
    async toggleMenu() {
      this.menuVisible = !this.menuVisible;
      // load our commits when the menu is not yet visible (it'll be toggled after loading)
      // and we got no commits
      if (!this.commits.length && this.menuVisible && !this.isLoading) {
        this.isLoading = true;
        try {
          await this.fetchCommits();
        } finally {
          this.isLoading = false;
        }
      }
      // set correct tabindex to allow easier navigation
      this.$nextTick(() => {
        if (this.menuVisible) {
          this.focusElem(this.$refs.showAllChanges as HTMLElement, this.$refs.expandBtn as HTMLElement);
        } else {
          this.focusElem(this.$refs.expandBtn as HTMLElement, this.$refs.showAllChanges as HTMLElement);
        }
      });
    },

    /** Load the commits to show in this dropdown */
    async fetchCommits() {
      const resp = await GET(`${this.issueLink}/commits/list`);
      const results = await resp.json() as CommitListResult;
      this.commits.push(...results.commits.map((x) => {
        x.hovered = false;
        return x;
      }));
      this.commits.reverse();
      this.lastReviewCommitSha = results.last_review_commit_sha || null;
      if (this.lastReviewCommitSha && !this.commits.some((x) => x.id === this.lastReviewCommitSha)) {
        // the lastReviewCommit is not available (probably due to a force push)
        // reset the last review commit sha
        this.lastReviewCommitSha = null;
      }
      Object.assign(this.locale, results.locale);
    },
    showAllChanges() {
      window.location.assign(`${this.issueLink}/files${this.queryParams}`);
    },
    /** Called when user clicks on since last review */
    changesSinceLastReviewClick() {
      window.location.assign(`${this.issueLink}/files/${this.lastReviewCommitSha}..${this.commits.at(-1).id}${this.queryParams}`);
    },
    /** Clicking on a single commit opens this specific commit */
    commitClicked(commitId: string, newWindow = false) {
      const url = `${this.issueLink}/commits/${commitId}${this.queryParams}`;
      if (newWindow) {
        window.open(url);
      } else {
        window.location.assign(url);
      }
    },
    /**
     * When a commit is clicked while holding Shift, it enables range selection.
     * - The range selection is a half-open, half-closed range, meaning it excludes the start commit but includes the end commit.
     * - The start of the commit range is always the previous commit of the first clicked commit.
     * - If the first commit in the list is clicked, the mergeBase will be used as the start of the range instead.
     * - The second Shift-click defines the end of the range.
     * - Once both are selected, the diff view for the selected commit range will open.
     */
    commitClickedShift(commit: Commit) {
      this.hoverActivated = !this.hoverActivated;
      commit.selected = true;
      // Second click -> determine our range and open links accordingly
      if (!this.hoverActivated) {
        // since at least one commit is selected, we can determine the range
        // find all selected commits and generate a link
        const firstSelected = this.commits.findIndex((x) => x.selected);
        const lastSelected = this.commits.findLastIndex((x) => x.selected);
        let beforeCommitID: string;
        if (firstSelected === 0) {
          beforeCommitID = this.mergeBase;
        } else {
          beforeCommitID = this.commits[firstSelected - 1].id;
        }
        const afterCommitID = this.commits[lastSelected].id;

        if (firstSelected === lastSelected) {
          // if the start and end are the same, we show this single commit
          window.location.assign(`${this.issueLink}/commits/${afterCommitID}${this.queryParams}`);
        } else if (beforeCommitID === this.mergeBase && afterCommitID === this.commits.at(-1).id) {
          // if the first commit is selected and the last commit is selected, we show all commits
          window.location.assign(`${this.issueLink}/files${this.queryParams}`);
        } else {
          window.location.assign(`${this.issueLink}/files/${beforeCommitID}..${afterCommitID}${this.queryParams}`);
        }
      }
    },
  },
});
</script>
<template>
  <div class="ui scrolling dropdown custom diff-commit-selector">
    <button
      ref="expandBtn"
      class="ui tiny basic button"
      @click.stop="toggleMenu()"
      :data-tooltip-content="locale.filter_changes_by_commit"
      aria-haspopup="true"
      :aria-label="locale.filter_changes_by_commit"
      :aria-controls="uniqueIdMenu"
      :aria-activedescendant="uniqueIdShowAll"
    >
      <svg-icon name="octicon-git-commit"/>
    </button>
    <!-- this dropdown is not managed by Fomantic UI, so it needs some classes like "transition" explicitly -->
    <div class="left menu transition" :id="uniqueIdMenu" :class="{visible: menuVisible}" v-show="menuVisible" v-cloak :aria-expanded="menuVisible ? 'true': 'false'">
      <div class="loading-indicator is-loading" v-if="isLoading"/>
      <div v-if="!isLoading" class="item" :id="uniqueIdShowAll" ref="showAllChanges" role="menuitem" @keydown.enter="showAllChanges()" @click="showAllChanges()">
        <div class="gt-ellipsis">
          {{ locale.show_all_commits }}
        </div>
        <div class="gt-ellipsis text light-2 tw-mb-0">
          {{ locale.stats_num_commits }}
        </div>
      </div>
      <!-- only show the show changes since last review if there is a review AND we are commits ahead of the last review -->
      <div
        v-if="lastReviewCommitSha != null"
        class="item" role="menuitem"
        :class="{disabled: !commitsSinceLastReview}"
        @keydown.enter="changesSinceLastReviewClick()"
        @click="changesSinceLastReviewClick()"
      >
        <div class="gt-ellipsis">
          {{ locale.show_changes_since_your_last_review }}
        </div>
        <div class="gt-ellipsis text light-2">
          {{ commitsSinceLastReview }} commits
        </div>
      </div>
      <span v-if="!isLoading" class="info text light-2">{{ locale.select_commit_hold_shift_for_range }}</span>
      <template v-for="(commit, idx) in commits" :key="commit.id">
        <div
          class="item" role="menuitem"
          :class="{selected: commit.selected, hovered: commit.hovered}"
          :data-commit-idx="idx"
          @keydown.enter.exact="commitClicked(commit.id)"
          @keydown.enter.shift.exact="commitClickedShift(commit)"
          @mouseover.shift="highlight(commit)"
          @click.exact="commitClicked(commit.id)"
          @click.ctrl.exact="commitClicked(commit.id, true)"
          @click.meta.exact="commitClicked(commit.id, true)"
          @click.shift.exact.stop.prevent="commitClickedShift(commit)"
        >
          <div class="tw-flex-1 tw-flex tw-flex-col tw-gap-1">
            <div class="gt-ellipsis commit-list-summary">
              {{ commit.summary }}
            </div>
            <div class="gt-ellipsis text light-2">
              {{ commit.committer_or_author_name }}
              <span class="text right">
                <!-- TODO: make this respect the PreferredTimestampTense setting -->
                <relative-time prefix="" :datetime="commit.time" data-tooltip-content data-tooltip-interactive="true">{{ commit.time }}</relative-time>
              </span>
            </div>
          </div>
          <div class="tw-font-mono">
            {{ commit.short_sha }}
          </div>
        </div>
      </template>
    </div>
  </div>
</template>
<style scoped>
  .ui.dropdown.diff-commit-selector .menu {
    margin-top: 0.25em;
    overflow-x: hidden;
    max-height: 450px;
  }

  .ui.dropdown.diff-commit-selector .menu .loading-indicator {
    height: 200px;
    width: 350px;
  }

  .ui.dropdown.diff-commit-selector .menu > .item,
  .ui.dropdown.diff-commit-selector .menu > .info {
    display: flex;
    flex-direction: row;
    line-height: 1.4;
    gap: 0.25em;
    padding: 7px 14px !important;
  }

  .ui.dropdown.diff-commit-selector .menu > .item:not(:first-child),
  .ui.dropdown.diff-commit-selector .menu > .info:not(:first-child) {
    border-top: 1px solid var(--color-secondary) !important;
  }

  .ui.dropdown.diff-commit-selector .menu > .item:focus {
    background: var(--color-active);
  }

  .ui.dropdown.diff-commit-selector .menu > .item.hovered {
    background-color: var(--color-small-accent);
  }

  .ui.dropdown.diff-commit-selector .menu > .item.selected {
    background-color: var(--color-accent);
  }

  .ui.dropdown.diff-commit-selector .menu .commit-list-summary {
    max-width: min(380px, 96vw);
  }
</style>
